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BEGIN:VEVENT
SUMMARY:Rui Loja Fernandes (University of Illinois at Urbana-Champaign)
DTSTART:20200512T160000Z
DTEND:20200512T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/1
DESCRIPTION:Title: Non-commutative integrable systems and their singularities\nby R
ui Loja Fernandes (University of Illinois at Urbana-Champaign) as part of
Geometria em Lisboa (IST)\n\n\nAbstract\nThe theory of singularities of no
n-commutative integrable systems (a.k.a isotropic fibrations)\, in contras
t with the well-known theory for the commutative case (a.k.a. Lagrangian f
ibrations)\, is nonexistent. In this talk I will describe a few first step
s toward such a theory.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michael Singer (University College London)
DTSTART:20200519T153000Z
DTEND:20200519T163000Z
DTSTAMP:20260404T094148Z
UID:Geolis/2
DESCRIPTION:Title: A construction of $D_k$ asymptotically locally flat gravitational in
stantons from Atiyah-Hitchin and Taub-NUT geometries\nby Michael Singe
r (University College London) as part of Geometria em Lisboa (IST)\n\n\nAb
stract\nComplete hyperKaehler 4-manifolds with cubic volume growth (and su
itable decay of the curvature)\, also known as ALF gravitational instanton
s\, are known to come in two families\, according to the `fundamental grou
p at infinity’. This group must be a finite subgroup of $SU(2)$ and the
only possibilities compatible with cubic volume growth are the cyclic grou
ps ($A_k$) and binary dihedral groups ($D_k$).\n\nThis talk will be about
the construction of $D_k$ ALF gravitational instantons by a gluing constru
ction in which the ingredients are the moduli space of centred charge-2 mo
nopoles ($D_0$) and a particularly symmetric\, but singular\, $A_k$ ALF gr
avitational instanton. This construction was suggested in a paper of Sen (
1997). It is also closely related to a construction due to Foscolo\, in wh
ich hyperKaehler metrics are constructed on the $K3$ manifold that are `ne
arly’ collapsed to a 3-dimensional space.\n\nThis is joint work with Ber
nd Schroers.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xavier Roulleau (Université d’Aix-Marseille)
DTSTART:20200526T160000Z
DTEND:20200526T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/3
DESCRIPTION:Title: On a special configuration of 12 conics and a related K3 surface\nby Xavier Roulleau (Université d’Aix-Marseille) as part of Geometria
em Lisboa (IST)\n\n\nAbstract\nA generalized Kummer surface $X$ obtained
as the quotient of an abelian surface by a symplectic automorphism of orde
r 3 contains a $9{\\mathbf A}_{2}$-configuration of $(-2)$-curves (ie smoo
th rational curves). Such a configuration plays the role of the $16$ disjo
int $(-2)$-curves for the usual Kummer surfaces.
\nIn this talk we will
explain how construct $9$ other such $9{\\mathbf A}_{2}$-configurations o
n the generalized Kummer surface associated to the double cover of the pla
ne branched over the sextic dual curve of a cubic curve.
\nThe new $9{
\\mathbf A}_{2}$-configurations are obtained by taking the pullback of a c
ertain configuration of $12$ conics which are in special position with res
pect to the branch curve\, plus some singular quartic curves. We will then
explain how construct some automorphisms of the K3 surface sending one co
nfiguration to another.
\n(Joint work with David Kohel and Alessandra
Sarti).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Steve Zelditch (Northwestern University)
DTSTART:20200602T160000Z
DTEND:20200602T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/4
DESCRIPTION:Title: Probabilistic aspects of toric Kähler geometry\nby Steve Zeldit
ch (Northwestern University) as part of Geometria em Lisboa (IST)\n\n\nAbs
tract\nLet $(M\, \\omega\, L)$ be a polarized toric Kahler manifold with p
olytope $P$. Associated to this data is a family $\\mu_k^x$ of probability
measures on $P$ parametrized by $x \\in P.$ They generalize the multi-nom
ial measures on the simplex\, where $M = \\mathbb{CP}^n$ and $\\omega$ is
the Fubini-Study measure. As is well-known\, these measures satisfy a law
of large numbers\, a central limit theorem\, a large deviations principle
and entropy asymptotics. The measure of maximal entropy in this family cor
responds to the center of mass $x$ of $P$. All of these results generalize
to any toric Kahler manifold\, except the center of mass result\, which h
olds for Fano toric Kahler-Einstein manifolds.\n\nJoint work with Peng Zho
u and Pierre Flurin.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alessia Mandini (IST and Universidade Federal Fluminense)
DTSTART:20200616T160000Z
DTEND:20200616T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/5
DESCRIPTION:Title: Quasi-parabolic Higgs bundles and null hyperpolygon spaces\nby A
lessia Mandini (IST and Universidade Federal Fluminense) as part of Geomet
ria em Lisboa (IST)\n\n\nAbstract\nHyperpolygons spaces are a family of hy
perkähler manifolds\, that can be obtained from coadjoint orbits by hyper
kähler reduction. Jointly with L. Godinho\, we showed that these space ar
e isomorphic to certain families of parabolic Higgs bundles\, when a suita
ble condition between the parabolic weights and the spectra of the coadjoi
nt orbits is satisfied.\n\nIn analogy to this construction\, we introduce
two moduli spaces: the moduli spaces of quasi-parabolic $SL(2\,\\mathbb{C}
)$-Higgs bundles over $\\mathbb{CP}^1$ on one hand and the null hyperpolyg
on spaces on the other\, and establish an isomorphism between them.\nFinal
ly we describe the fixed loci of natural involutions defined on these spac
es and relate them to the moduli space of null hyperpolygons in the Minkow
ski $3$-space.\n\nThis is based in joint works with Leonor Godinho.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mario Garcia-Fernandez (ICMAT and Universidad Autónoma de Madrid)
DTSTART:20200623T160000Z
DTEND:20200623T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/6
DESCRIPTION:Title: Gauge theory for string algebroids\nby Mario Garcia-Fernandez (I
CMAT and Universidad Autónoma de Madrid) as part of Geometria em Lisboa (
IST)\n\n\nAbstract\nIn this talk I will overview recent joint work with Ro
berto Rubio and Carl Tipler in arXiv:2004.11399. We introduce a moment map
picture for string algebroids\, a special class of holomorphic Courant al
gebroids introduced in arXiv:1807.10329. An interesting feature of our con
struction is that the Hamiltonian gauge action is described by means of Mo
rita equivalences\, as suggested by higher gauge theory. The zero locus of
the moment map is given by the solutions of the Calabi system\, a coupled
system of equations which provides a unifying framework for the classical
Calabi problem and the Hull-Strominger system. Our main results are conce
rned with the geometry of the moduli space of solutions. Assuming a techni
cal condition\, we prove that the moduli space carries a pseudo-Kähler me
tric with Kähler potential given by the 'dilaton functional'\, a topologi
cal formula for the metric\, and an infinitesimal Donaldson-Uhlenbeck-Yau
type theorem. Finally\, we relate our topological formula to a physical pr
ediction for the gravitino mass in order to obtain a new conjectural obstr
uction for the Hull-Strominger system.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tara Holm (Cornell University)
DTSTART:20200630T160000Z
DTEND:20200630T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/7
DESCRIPTION:Title: Symplectic embeddings and infinite staircases\nby Tara Holm (Cor
nell University) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nMcDuf
f and Schlenk determined when a four-dimensional symplectic ellipsoid can
be symplectically embedded into a four-dimensional ball. They found that i
f the ellipsoid is close to round\, the answer is given by an infinite sta
ircase determined by Fibonacci numbers\, while if the ellipsoid is suffici
ently stretched\, all obstructions vanish except for the volume obstructio
n. Infinite staircases have also been found when embedding ellipsoids into
polydisks (Frenkel - Muller\, Usher) and into the ellipsoid E(2\,3) (Cris
tofaro-Gardiner - Kleinman). We will describe a general approach to the qu
estion of when embedding ellipsoids into a toric target has an infinite st
aircase\, where we provide the first obstruction to the existence of a sta
ircase. We use this obstruction to explore infinite staircases for toric s
ymplectic manifolds\, identifying three new infinite staircases\, and culm
inating in the conjecture that these are the only toric examples. We will
describe further work-in-progress on ellipsoid embedding functions with mo
re general targets. I will not assume any prior acquaintance with infinite
staircases and will motivate the talk with plentiful examples and picture
s. This talk is based on a number of collaborations with Dan Cristofaro-Ga
rdiner\, Alessia Mandini\, and Ana Rita Pires\; Maria Bertozzi\, Emily Maw
\, Dusa McDuff\, Grace Mwakyoma\, Ana Rita Pires\, Morgan Weiler\; and Nic
ki Magill.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kai Cieliebak (Augsburg University)
DTSTART:20200609T160000Z
DTEND:20200609T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/8
DESCRIPTION:Title: Partial orders on contactomorphism groups and their Lie algebras
\nby Kai Cieliebak (Augsburg University) as part of Geometria em Lisboa (I
ST)\n\n\nAbstract\nEliashberg\, Kim and Polterovich constructed nontrivial
partial orders on contactomorphism groups of certain contact manifolds. A
fter recalling their results\, the subject of this talk will be the remnan
ts of these partial orders on the orbits of the coadjoint action on their
Lie algebras.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tian-Jun Li (University of Minnesota)
DTSTART:20200714T160000Z
DTEND:20200714T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/9
DESCRIPTION:Title: Symplectic rational G-surfaces and the plane Cremona group\nby T
ian-Jun Li (University of Minnesota) as part of Geometria em Lisboa (IST)\
n\n\nAbstract\nWe give characterizations of a finite group $G$ acting symp
lectically on a rational surface ($\\mathbb{CP}^2$ blown up at two or more
points). In particular\, we obtain a symplectic version of the dichotomy
of $G$-conic bundles versus $G$-del Pezzo surfaces for the corresponding $
G$-rational surfaces\, analogous to the one in algebraic geometry. The con
nection with the symplectic mapping class group will be mentioned.\n\n\nTh
is is a joint work with Weimin Chen and Weiwei Wu (and partly with Jun Li)
.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rahul Pandharipande (ETH Zürich)
DTSTART:20200707T160000Z
DTEND:20200707T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/10
DESCRIPTION:Title: Moduli spaces of differentials on curves\nby Rahul Pandharipand
e (ETH Zürich) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nThe mo
duli of $(C\,f)$ where $C$ is a curve and $f$ is a rational function leads
to the well-developed theory of Hurwitz spaces. The study of the moduli o
f $(C\,\\omega)$ where $C$ is a curve and $\\omega$ is a meromorphic di
fferential is a younger subject. I will discuss recent developments in the
study of the moduli spaces of holomorphic/meromorphic differentials on cu
rves. Many of the basic questions about cycle classes and integrals have n
ow been solved (through the work of many people) -- but there are also sev
eral interesting open directions.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Colin Guillarmou (Laboratoire de Mathématiques d'Orsay\, Universi
té Paris-Sud)
DTSTART:20200721T160000Z
DTEND:20200721T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/11
DESCRIPTION:Title: On the marked length spectrum and geodesic stretch in negative curv
ature\nby Colin Guillarmou (Laboratoire de Mathématiques d'Orsay\, Un
iversité Paris-Sud) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nI
will review a couple of recent of results proved with T. Lefeuvre and G.
Knieper on the local rigidity of the marked length spectrum of negatively
curved metrics.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mark Gross (Department of Pure Mathematics and Mathematical Statis
tics\, University of Cambridge)
DTSTART:20200728T160000Z
DTEND:20200728T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/12
DESCRIPTION:Title: Intrinsic Mirror Symmetry\nby Mark Gross (Department of Pure Ma
thematics and Mathematical Statistics\, University of Cambridge) as part o
f Geometria em Lisboa (IST)\n\n\nAbstract\nI will talk about joint work wi
th Bernd Siebert\, proposing a general mirror construction for log Calabi-
Yau pairs\, i.e.\, a pair $(X\,D)$ with $D$ a "maximally degenerate" bound
ary divisor and $K_X+D=0$\, and for maximally unipotent degenerations of C
alabi - Yau manifolds. We accomplish this by constructing the coordinate r
ing or homogeneous coordinate ring respectively in the two cases\, using c
ertain kinds of Gromov-Witten invariants we call "punctured invariants"\,
developed jointly with Abramovich and Chen.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Robert Berman (Chalmers University of Technology)
DTSTART:20200915T100000Z
DTEND:20200915T110000Z
DTSTAMP:20260404T094148Z
UID:Geolis/13
DESCRIPTION:Title: Kähler-Einstein metrics\, Archimedean Zeta functions and phase tra
nsitions\nby Robert Berman (Chalmers University of Technology) as part
of Geometria em Lisboa (IST)\n\n\nAbstract\nWhile the existence of a uniq
ue Kähler-Einstein metrics on a canonically polarized manifold $X$ was es
tablished already in the seventies there are very few explicit formulas av
ailable (even in the case of complex curves!). In this talk I will give a
non-technical introduction to a probabilistic approach to Kähler-Einstein
metrics\, which\, in particular\, yields canonical approximations of the
Kähler-Einstein metric on $X$. The approximating metrics in question are
expressed as explicit period integrals and the conjectural extension to th
e case of a Fano variety leads to some intriguing connections with Zeta fu
nctions and the theory of phase transitions in statistical mechanics.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gonçalo Oliveira (Universidade Federal Fluminense\, Brazil)
DTSTART:20200929T160000Z
DTEND:20200929T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/14
DESCRIPTION:Title: $G_2$-monopoles (a summary)\nby Gonçalo Oliveira (Universidade
Federal Fluminense\, Brazil) as part of Geometria em Lisboa (IST)\n\n\nAb
stract\nThis talk is aimed at reviewing what is known about $G_2$-monopole
s and motivate their study. After this\, I will mention some recent result
s obtained in collaboration with Ákos Nagy and Daniel Fadel which investi
gate the asymptotic behavior of $G_2$-monopoles. Time permitting\, I will
mention a few possible future directions regarding the use of monopoles in
$G_2$-geometry.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Éveline Legendre (Université Paul Sabatier)
DTSTART:20201006T160000Z
DTEND:20201006T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/15
DESCRIPTION:Title: Localizing the Donaldson-Futaki invariant\nby Éveline Legendre
(Université Paul Sabatier) as part of Geometria em Lisboa (IST)\n\n\nAbs
tract\nWe will see how to represent the Donaldson-Futaki invariant as an i
ntersection of equivariant closed forms. We will use it to express this in
variant as the intersection on some specific subvarieties of the central f
ibre of the test configuration. As an application we provide a proof that
for Kähler orbifolds the Donaldson-Futaki invariant is the Futaki invaria
nt of the central fiber.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sílvia Anjos (Instituto Superior Técnico and CAMGSD)
DTSTART:20201117T170000Z
DTEND:20201117T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/16
DESCRIPTION:Title: Loops in the fundamental group of $\\mathrm{Symp}(M\,\\omega)$ whic
h are not represented by circle actions\nby Sílvia Anjos (Instituto S
uperior Técnico and CAMGSD) as part of Geometria em Lisboa (IST)\n\n\nAbs
tract\nIt was observed by J. Kędra that there are many symplectic 4-manif
olds $(M\, \\omega)$\, where $M$ is neither rational nor ruled\, that admi
t no circle action and $\\pi_1 (\\mathrm{Ham}( M))$ is nontrivial. In the
case $M={\\mathbb C\\mathbb P}^2\\#\\\,k\\overline{\\mathbb C\\mathbb P}\\
\,\\!^2$\, with $k \\leq 4$\, it follows from the work of several authors
that the full rational homotopy of $\\mathrm{Symp}(M\,\\omega)$\, and in p
articular their fundamental group\, is generated by circle actions on the
manifold. In this talk we study loops in the fundamental group of $\\mathr
m{Symp}_h({\\mathbb C\\mathbb P}^2\\#\\\,5\\overline{\\mathbb C\\mathbb P}
\\\,\\!^2) $ of symplectomorphisms that act trivially on homology\, and sh
ow that\, for some particular symplectic forms\, there are loops which can
not be realized by circle actions. Our work depends on Delzant classificat
ion of toric symplectic manifolds and Karshon's classification of Hamilton
ian circle actions\n\nThis talk is based in joint work with Miguel Barata\
, Martin Pinsonnault and Ana Alexandra Reis.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nick Sheridan (University of Edinburgh)
DTSTART:20200908T160000Z
DTEND:20200908T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/17
DESCRIPTION:Title: Lagrangian cobordism and Chow groups\nby Nick Sheridan (Univers
ity of Edinburgh) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nHomo
logical mirror symmetry predicts an equivalence of categories\, between th
e Fukaya category of one space and the derived category of another. We can
"decategorify" by taking the Grothendieck group of these categories\, to
get an isomorphism of abelian groups. The first of these abelian groups is
related\, by work of Biran-Cornea\, to the Lagrangian cobordism group\; t
he second is related\, via the Chern character\, to the Chow group. I will
define the Lagrangian cobordism and Chow groups (which is much easier tha
n defining the categories). Then I will describe joint work with Ivan Smit
h in which we try to compare them directly\, and find some interesting ana
logies.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ana Rita Pires (University of Edinburgh)
DTSTART:20200202T170000Z
DTEND:20200202T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/18
DESCRIPTION:Title: Many more infinite staircases in symplectic embedding functions
\nby Ana Rita Pires (University of Edinburgh) as part of Geometria em Lisb
oa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yang Li (Institute for Advanced Study)
DTSTART:20200922T160000Z
DTEND:20200922T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/19
DESCRIPTION:Title: Weak SYZ conjecture for hypersurfaces in the Fermat family\nby
Yang Li (Institute for Advanced Study) as part of Geometria em Lisboa (IST
)\n\n\nAbstract\nThe SYZ conjecture predicts that for polarised Calabi-Yau
manifolds undergoing the large complex structure limit\, there should be
a special Lagrangian torus fibration. A weak version asks if this fibratio
n can be found in the generic region. I will discuss my recent work provin
g this weak SYZ conjecture for the degenerating hypersurfaces in the Ferma
t family. Although these examples are quite special\, this is the first co
nstruction of generic SYZ fibrations that works uniformly in all complex d
imensions.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xiuxiong Chen (Stony Brook University)
DTSTART:20201013T160000Z
DTEND:20201013T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/20
DESCRIPTION:Title: On the space of Kähler metrics\nby Xiuxiong Chen (Stony Brook
University) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nInspired b
y the celebrated $C^0\, C^2$ and $C^3$ a priori estimate of Calabi\, Yau a
nd others on Kähler Einstein metrics\, we will present an expository repo
rt of a priori estimates on the constant scalar curvature Kähler metrics.
With this estimate\, we prove the Donaldson conjecture on geodesic stabil
ity and the properness conjecture on Mabuchi energy functional.\n\nThis is
a joint work with Cheng JingRui.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leonardo Macarini (Instituto Superior Técnico and CAMGSD)
DTSTART:20201124T170000Z
DTEND:20201124T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/21
DESCRIPTION:Title: Dynamical implications of convexity beyond dynamical convexity\
nby Leonardo Macarini (Instituto Superior Técnico and CAMGSD) as part of
Geometria em Lisboa (IST)\n\n\nAbstract\nWe will show sharp dynamical impl
ications of convexity on symmetric spheres that do not follow from dynamic
al convexity. It allows us to furnish new examples of dynamically convex c
ontact forms that are not equivalent to convex ones via contactomorphisms
that preserve the symmetry. Moreover\, these examples are $C^1$-stable in
the sense that they are actually not equivalent to convex ones via contact
omorphisms that are $C^1$-close to those preserving the symmetry. Other ap
plications are the multiplicity of symmetric non-hyperbolic closed Reeb or
bits under suitable pinching conditions and the existence of symmetric ell
iptic periodic Reeb orbits. \n\nThis is ongoing joint work with Miguel Abr
eu.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tristan C. Collins (MIT)
DTSTART:20201020T160000Z
DTEND:20201020T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/22
DESCRIPTION:Title: SYZ mirror symmetry for del Pezzo surfaces and rational elliptic su
rfaces\nby Tristan C. Collins (MIT) as part of Geometria em Lisboa (IS
T)\n\n\nAbstract\nI will discuss some aspects of SYZ mirror symmetry for p
airs $(X\,D)$ where $X$ is a del Pezzo surface or a rational elliptic surf
ace and $D$ is an anti-canonical divisor. In particular I will explain t
he existence of special Lagrangian fibrations\, mirror symmetry for (suita
bly interpreted) Hodge numbers and\, if time permits\, I will describe a p
roof of SYZ mirror symmetry conjecture for del Pezzo surfaces. \n\nThis
is joint work with Adam Jacob and Yu-Shen Lin.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrew Lobb (Durham University)
DTSTART:20201103T170000Z
DTEND:20201103T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/23
DESCRIPTION:Title: The rectangular peg problem\nby Andrew Lobb (Durham University)
as part of Geometria em Lisboa (IST)\n\n\nAbstract\nFor any smooth Jordan
curve and rectangle in the plane\, we show that there exist four points o
n the Jordan curve forming the vertices of a rectangle similar to the give
n one.\nJoint work with Josh Greene.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yaron Ostrover (Tel Aviv University)
DTSTART:20201027T170000Z
DTEND:20201027T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/24
DESCRIPTION:Title: On symplectic inner and outer radii of some convex domains\nby
Yaron Ostrover (Tel Aviv University) as part of Geometria em Lisboa (IST)\
n\n\nAbstract\nSymplectic embedding problems are at the heart of the study
of symplectic topology. In this talk we discuss how to use integrable sys
tems to compute the symplectic inner and outer radii of certain convex dom
ains.\n\nThe talk is based on a joint work with Vinicius Ramos.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simon K. Donaldson (Simons Center for Geometry and Physics Stony B
rook and Imperial College London)
DTSTART:20201215T170000Z
DTEND:20201215T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/25
DESCRIPTION:Title: Co-associative fibrations of $G_{2}$-manifolds and deformations of
singular sets\nby Simon K. Donaldson (Simons Center for Geometry and P
hysics Stony Brook and Imperial College London) as part of Geometria em Li
sboa (IST)\n\n\nAbstract\nThe first part of the talk will review backgroun
d material on the differential geometry of $7$-dimensional manifolds with
the exceptional holonomy group $G_{2}$. There are now many thousands of ex
amples of deformation classes of such manifolds and there are good reasons
for thinking that many of these have fibrations with general fibre diffeo
morphic to a $K3$ surface and some singular fibres: higher dimensional ana
logues of Lefschetz fibrations in algebraic geometry. In the second part o
f the talk we will discuss some questions which arise in the analysis of t
hese fibrations and their "adiabatic limits". The key difficulties involve
the singular fibres. This brings up a PDE problem\, analogous to a free b
oundary problem\, and similar problems have arisen in a number of areas of
differential geometry over the past few years\, such as in Taubes' work o
n gauge theory. We will outline some techniques for handling these questio
ns.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leonor Godinho (Instituto Superior Técnico and CAMGSD)
DTSTART:20210309T170000Z
DTEND:20210309T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/26
DESCRIPTION:Title: On the number of fixed points of periodic flows\nby Leonor Godi
nho (Instituto Superior Técnico and CAMGSD) as part of Geometria em Lisbo
a (IST)\n\n\nAbstract\nFinding the minimal number of fixed points of a per
iodic flow on a compact manifold is\, in general\, an open problem. We wil
l consider almost complex manifolds and see how one can obtain lower bound
s by retrieving information from a special Chern number.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Paul Biran (ETH Zurich)
DTSTART:20210202T170000Z
DTEND:20210202T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/27
DESCRIPTION:Title: Persistence and Triangulation in Lagrangian Topology\nby Paul B
iran (ETH Zurich) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nBoth
triangulated categories as well as persistence homology play an important
role in symplectic topology. The goal of this talk is to explain how to p
ut the two structures\ntogether\, leading to the notion of a triangulated
persistence category. The guiding principle comes from the theory of Lagra
ngian cobordism.\n\nThe talk is based on ongoing joint work with Octav Cor
nea and Jun Zhang.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dusa McDuff (Columbia University)
DTSTART:20210112T170000Z
DTEND:20210112T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/28
DESCRIPTION:Title: Counting curves and stabilized symplectic embedding conjecture\
nby Dusa McDuff (Columbia University) as part of Geometria em Lisboa (IST)
\n\n\nAbstract\nThis is a report on joint work with Kyler Siegel that deve
lops new ways to count $J$-holomorphic curves in $4$-dimensions\, both in
the projective plane with multi-branched tangency constraints\, and in non
compact cobordisms between ellipsoids. These curves stabilize\, i.e. if th
ey exist in a given four dimensional target manifold $X$ they still exist
in the product $X \\times {\\mathbb R}^{2k}$. This allows us to establish
new cases of the stabilized embedding conjecture for symplectic embeddings
of an ellipsoid into a ball (or ellipsoid).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thibaut Delcroix (Université de Montpellier)
DTSTART:20210105T170000Z
DTEND:20210105T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/29
DESCRIPTION:Title: On the Yau-Tian-Donaldson conjecture for spherical varieties\nb
y Thibaut Delcroix (Université de Montpellier) as part of Geometria em Li
sboa (IST)\n\n\nAbstract\nI will present how uniform $K-$stability transla
tes into a convex geometric problem for polarized spherical varieties.\nFr
om this\, we will derive a combinatorial sufficient condition of existence
of constant scalar curvature Kahler metrics on smooth singular varieties\
, and a complete solution to the Yau-Tian-Donaldson conjecture for cohomog
eneity one manifolds.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vicente Muñoz (Málaga University)
DTSTART:20210209T170000Z
DTEND:20210209T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/30
DESCRIPTION:Title: A Smale-Barden manifold admitting K-contact but not Sasakian struct
ure\nby Vicente Muñoz (Málaga University) as part of Geometria em Li
sboa (IST)\n\n\nAbstract\nSasakian manifolds are odd-dimensional counterpa
rts of Kahler manifolds in even dimensions\, with K-contact manifolds corr
esponding to symplectic manifolds. In this talk\, we give the first exampl
e of a simply connected compact 5-manifold (Smale-Barden manifold) which a
dmits a\nK-contact structure but does not admit any Sasakian structure\, s
ettling a long standing question of Boyer and Galicki. \n\nFor this\, we t
ranslate the question about K-contact 5-manifolds to constructing symplect
ic 4-orbifolds with cyclic singularities containing disjoint symplectic su
rfaces of positive genus. The question on Sasakian 5-manifolds translates
to the existence of algebraic surfaces with\ncyclic singularities containi
g disjoint complex curves of positive genus. A key step consists on boundi
ng universally the number of singular points of the algebraic surface.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emilio Franco (Instituto Superior Técnico and CAMGSD)
DTSTART:20201110T170000Z
DTEND:20201110T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/31
DESCRIPTION:Title: Torsion line bundles and branes on the Hitchin system\nby Emili
o Franco (Instituto Superior Técnico and CAMGSD) as part of Geometria em
Lisboa (IST)\n\n\nAbstract\nThe locus of the Higgs moduli space fixed unde
r tensorization by a torsion line bundle a key role in the work of Hausel
and Thaddeus on topological mirror symmetry. We shall describe the behavio
r under mirror symmetry of this fixed locus.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jonathan Weitsman (Northeastern University)
DTSTART:20210216T170000Z
DTEND:20210216T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/32
DESCRIPTION:by Jonathan Weitsman (Northeastern University) as part of Geom
etria em Lisboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexandru Oancea (Institut de Mathématiques de Jussieu\, Sorbonne
Université)
DTSTART:20210223T170000Z
DTEND:20210223T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/33
DESCRIPTION:Title: Duality and coproducts in Rabinowitz-Floer homology\nby Alexand
ru Oancea (Institut de Mathématiques de Jussieu\, Sorbonne Université) a
s part of Geometria em Lisboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cristiano Spotti (Aarhus University)
DTSTART:20210126T170000Z
DTEND:20210126T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/34
DESCRIPTION:by Cristiano Spotti (Aarhus University) as part of Geometria e
m Lisboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Justin Sawon (University of North Carolina at Chapel Hill)
DTSTART:20210119T170000Z
DTEND:20210119T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/35
DESCRIPTION:Title: Lagrangian fibrations by Prym varieties\nby Justin Sawon (Unive
rsity of North Carolina at Chapel Hill) as part of Geometria em Lisboa (IS
T)\n\n\nAbstract\nLagrangian fibrations on holomorphic symplectic manifold
s and orbifolds are higher-dimensional generalizations of elliptic K3 surf
aces. They are fibrations whose general fibres are abelian varieties that
are Lagrangian with respect to the symplectic form. Markushevich and Tikho
mirov described the first example whose fibres are Prym varieties\, and th
eir construction was further developed by Arbarello\, Ferretti\, and Sacca
and by Matteini to yield more examples. In this talk we describe the gene
ral framework\, and consider a new example. We describe its singularities
and show that it is a 'primitive' symplectic variety. We also construct th
e dual fibration\, using ideas of Menet. This is joint work with Chen Shen
.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giulia Saccà (Columbia University)
DTSTART:20210316T170000Z
DTEND:20210316T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/36
DESCRIPTION:Title: Compact Hyper-Kählers and Fano Manifolds\nby Giulia Saccà (Co
lumbia University) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nPro
jective hyper-Kähler (HK) manifolds are among the building blocks of proj
ective manifolds with trivial first Chern class. Fano manifolds are projec
tive manifolds with positive first Chern class.\n\nDespite the fact that t
hese two classes of algebraic varieties are very different (HK manifolds h
ave a holomorphic symplectic form which governs all of its geometry\, Fano
manifolds have no holomorphic forms) their geometries have some strong ti
es. For example\, starting from some special Fano manifolds one can someti
mes construct HK manifolds as parameter spaces of objects on the Fano. In
this talk I will explain this circle of ideas and focus on some recent wor
k exploring the converse: given a projective HK manifold\, how to recover
a Fano manifold from it?\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrew Neitzke (Yale University)
DTSTART:20210302T170000Z
DTEND:20210302T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/37
DESCRIPTION:by Andrew Neitzke (Yale University) as part of Geometria em Li
sboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lorenzo Foscolo (University College London)
DTSTART:20210323T170000Z
DTEND:20210323T180000Z
DTSTAMP:20260404T094148Z
UID:Geolis/38
DESCRIPTION:Title: Twistor constructions of non-compact hyperkähler manifolds\nby
Lorenzo Foscolo (University College London) as part of Geometria em Lisbo
a (IST)\n\n\nAbstract\nThe talk is based on joint work with Roger Bielawsk
i about twistor constructions of higher dimensional non-compact hyperkähl
er manifolds with maximal and submaximal volume growth. In the first part
of the talk\, based on arXiv:2012.14895\, I will discuss the case of hyper
kähler metrics with maximal volume growth: in the same way that ALE space
s are closely related to the deformation theory of Kleinian singularities\
, we produce large families of hyperkähler metrics asymptotic to cones ex
ploiting the theory of Poisson deformations of affine symplectic singulari
ties. In the second part of the talk\, I will report on work in progress a
bout the construction of hyperkähler metrics generalising to higher dimen
sions the geometry of ALF spaces of dihedral type. We produce candidate ho
lomorphic symplectic manifolds and twistor spaces from Hilbert schemes of
hypertoric manifolds with an action of a Weyl group. The spaces we define
are closely related to Coulomb branches of 3-dimensional supersymmetric ga
uge theories.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Mazzuchelli (École normale supérieure de Lyon)
DTSTART:20210406T160000Z
DTEND:20210406T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/39
DESCRIPTION:Title: What does a Besse contact sphere look like?\nby Marco Mazzuchel
li (École normale supérieure de Lyon) as part of Geometria em Lisboa (IS
T)\n\n\nAbstract\nA closed connected contact manifold is called Besse when
all of its Reeb orbits are closed (the terminology comes from Arthur Bess
e's monograph "Manifolds all of whose geodesics are closed"\, which deals
indeed with Besse unit tangent bundles). In recent years\, a few intriguin
g properties of Besse contact manifolds have been established: in particul
ar\, their spectral and systolic characterizations. In this talk\, I will
focus on Besse contact spheres. In dimension 3\, it turns out that such sp
heres are strictly contactomorphic to rational ellipsoids. In higher dimen
sions\, an analogous result is unknown and seems out of reach. Nevertheles
s\, I will show that at least those contact spheres that are convex still
"resemble" a contact ellipsoid: any stratum of the stratification defined
by their Reeb flow is an integral homology sphere\, and the sequence of th
eir Ekeland-Hofer capacities coincides with the full sequence of action va
lues\, each one repeated according to a suitable multiplicity. This is joi
nt work with Marco Radeschi.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Brian Collier (University of California Riverside)
DTSTART:20210413T160000Z
DTEND:20210413T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/40
DESCRIPTION:Title: Global Slodowy slices for moduli spaces of λ-connections\nby B
rian Collier (University of California Riverside) as part of Geometria em
Lisboa (IST)\n\n\nAbstract\nThe moduli spaces of Higgs bundles and holomor
phic connections both have important affine holomorphic Lagrangian subvari
eties\, these are the Hitchin section and the space of opers\, respectivel
y. Both of these spaces arise from the same Lie theoretic mechanism\, name
ly a regular nilpotent element of a Lie algebra. In this talk we will gene
ralize these parameterizations to other nilpotents. The resulting objects
are not related by the nonabelian Hodge correspondence\, but by an operati
on called the conformal limit. Time permitting\, we will also discuss thei
r relation to Higher Teichmuller spaces.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tomasso Pacini (SNS Pisa)
DTSTART:20210420T160000Z
DTEND:20210420T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/41
DESCRIPTION:Title: Minimal Lagrangian submanifolds\, totally real geometry and the ant
i-canonical line bundle\nby Tomasso Pacini (SNS Pisa) as part of Geome
tria em Lisboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Laura Schaposnik (University of Illinois at Chicago)
DTSTART:20210427T160000Z
DTEND:20210427T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/42
DESCRIPTION:Title: On generalized hyperpolygons\nby Laura Schaposnik (University o
f Illinois at Chicago) as part of Geometria em Lisboa (IST)\n\n\nAbstract\
nIn this talk we will introduce generalized hyperpolygons\, which arise as
Nakajima-type representations of a comet-shaped quiver\, following recent
work joint with Steven Rayan. After showing how to identify these represe
ntations with pairs of polygons\, we shall associate to the data an explic
it meromorphic Higgs bundle on a\ngenus-g Riemann surface\, where g is the
number of loops in the comet. We shall see that\, under certain assumptio
ns on flag types\, the moduli space of generalized hyperpolygons admits th
e structure of a completely integrable Hamiltonian system.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yu-Shen Lin (Boston University)
DTSTART:20210504T160000Z
DTEND:20210504T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/43
DESCRIPTION:Title: Correspondence theorem between holomorphic discs and tropical discs
on (Log)-Calabi-Yau Surfaces\nby Yu-Shen Lin (Boston University) as p
art of Geometria em Lisboa (IST)\n\n\nAbstract\nTropical geometry is a use
ful tool to study the Gromov-Witten type invariants\, which count the numb
er of holomorphic curves with incidence conditions. On the other hand\, ho
lomorphic discs with boundaries on the Lagrangian fibration of a Calabi-Ya
u manifold plays an important role in the quantum correction of the mirror
complex structure. In this talk\, I will introduce a version of open Grom
ov-Witten invariants counting such discs and the corresponding tropical ge
ometry on (log) Calabi-Yau surfaces. Using Lagrangian Floer theory\, we wi
ll establish the equivalence between the open Gromov-Witten invariants wit
h weighted count of tropical discs. In particular\, the correspondence the
orem implies the folklore conjecture that certain open Gromov-Witten invar
iants coincide with the log Gromov-Witten invariants with maximal tangency
for the projective plane.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marcos Jardim (Campinas State University)
DTSTART:20210511T160000Z
DTEND:20210511T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/44
DESCRIPTION:Title: Walls and asymptotics for Bridgeland stability conditions on 3-fold
s\nby Marcos Jardim (Campinas State University) as part of Geometria e
m Lisboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carolina Araujo (IMPA)
DTSTART:20210601T160000Z
DTEND:20210601T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/45
DESCRIPTION:Title: Higher Fano Manifolds\nby Carolina Araujo (IMPA) as part of Geo
metria em Lisboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Camilla Felisetti (Università di Trento)
DTSTART:20210518T160000Z
DTEND:20210518T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/46
DESCRIPTION:Title: P=W conjectures for character varieties with a symplectic resolutio
n\nby Camilla Felisetti (Università di Trento) as part of Geometria e
m Lisboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Antoine Song (Princeton)
DTSTART:20210615T160000Z
DTEND:20210615T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/47
DESCRIPTION:Title: The essential minimal volume of manifolds\nby Antoine Song (Pri
nceton) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nOne way to mea
sure the complexity of a smooth manifold M is to consider its minimal volu
me\, denoted by MinVol\, introduced by Gromov\, which is simply defined as
the infimum of the volume among metrics with sectional curvature between
-1 and 1. I will introduce a variant of MinVol\, called the essential mini
mal volume\, defined as the infimum of the volume over a closure of the sp
ace of metrics with sectional curvature between -1 and 1. I will discuss t
he main properties of this invariant\, and present estimates for negativel
y curved manifolds\, Einstein 4-manifolds and most complex surfaces.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yael Karshon (University of Toronto)
DTSTART:20210622T160000Z
DTEND:20210622T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/48
DESCRIPTION:Title: Bott canonical basis?\nby Yael Karshon (University of Toronto)
as part of Geometria em Lisboa (IST)\n\n\nAbstract\nTogether with Jihyeon
Jessie Yang\, we are resurrecting an old idea of Raoul Bott for using larg
e torus actions to construct canonical bases for unitary representations o
f compact Lie groups. Our methods are complex analytic\; we apply them to
families of Bott-Samelson manifolds parametrized by C^n. Our construction
requires the vanishing of higher cohomology of sheaves of holomorphic sect
ions of certain line bundles over the total spaces of such families\; this
vanishing is conjectural\, hence the question mark in the title.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alberto Abbondandolo (Ruhr-Universität Bochum)
DTSTART:20210525T160000Z
DTEND:20210525T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/50
DESCRIPTION:Title: Systolic questions in metric and symplectic geometry\nby Albert
o Abbondandolo (Ruhr-Universität Bochum) as part of Geometria em Lisboa (
IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/50/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mirko Mauri (Max Planck (Bonn))
DTSTART:20210608T160000Z
DTEND:20210608T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/51
DESCRIPTION:Title: On the geometric P=W conjecture\nby Mirko Mauri (Max Planck (Bo
nn)) as part of Geometria em Lisboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Siu-Cheong Lau (Boston University)
DTSTART:20210706T160000Z
DTEND:20210706T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/52
DESCRIPTION:Title: Kaehler geometry of quiver moduli in application to machine learnin
g\nby Siu-Cheong Lau (Boston University) as part of Geometria em Lisbo
a (IST)\n\n\nAbstract\nNeural network in machine learning has interesting
similarity with quiver representation theory. In this talk\, I will build
an algebro-geometric formulation of a `computing machine'\, which is well
-defined over the moduli space of representations. The main algebraic ing
redient is to extend noncommutative geometry of Connes\, Cuntz-Quillen\, G
inzburg to near-rings\, which capture the non-linear activation functions
in neural network. I will also explain a uniformization between spherical
\, Euclidean and hyperbolic moduli of framed quiver representations.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Olivia Dumitrescu (University of North Carolina at Chapel Hill)
DTSTART:20210720T160000Z
DTEND:20210720T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/53
DESCRIPTION:Title: On stratifications and moduli\nby Olivia Dumitrescu (University
of North Carolina at Chapel Hill) as part of Geometria em Lisboa (IST)\n\
n\nAbstract\nThere exist two approaches to the conformal limit mechanism:
first was defined by Gaiotto using Analysis techniques and the method of c
omputing was first established for the Hitchin Section and Opers in 2016.
The second approach to conformal limits as algebraic shifts via extension
classes of vector bundles was established by Dumitrescu and Mulase in 2017
for the lagrangians Hitchin section and opers. In this talk I will report
on work in progress with Jennifer Brown and Motohico Mulase of the algebr
aic approach of conformal limits to a family of Lagrangians covering the D
olbeault and the De Rham moduli space of Higgs bundles and irreducible con
nections over a curve in rank 2.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Umberto Hryniewicz (Aachen University)
DTSTART:20210727T160000Z
DTEND:20210727T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/54
DESCRIPTION:Title: Contact three-manifolds with exactly two simple Reeb orbits\nby
Umberto Hryniewicz (Aachen University) as part of Geometria em Lisboa (IS
T)\n\n\nAbstract\nThe goal of this talk is to present a complete character
ization of Reeb flows on closed 3-manifolds with precisely two periodic or
bits. The main step consists in showing that a contact form with exactly t
wo periodic Reeb orbits is non-degenerate. The proof combines the ECH volu
me formula with a study of the behavior of the ECH index under non-degener
ate perturbations of the contact form. As a consequence\, the ambient cont
act 3-manifold is a standard lens space\, the contact form is dynamically
convex\, the Reeb flow admits a rational disk-like global surface of secti
on and the dynamics are described by a pseudorotation of the 2-disk. Moreo
ver\, the periods and rotation numbers of the closed orbits satisfy the sa
me relations as (quotients of) irrational ellipsoids\, and in the case of
S^3 the transverse knot-type of the periodic orbits is determined. Joint w
ork with Cristofaro-Gardiner\, Hutchings and Liu.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniele Alessandrini (Columbia University)
DTSTART:20210907T153000Z
DTEND:20210907T163000Z
DTSTAMP:20260404T094148Z
UID:Geolis/55
DESCRIPTION:Title: The nilpotent cone in rank one and minimal surfaces\nby Daniele
Alessandrini (Columbia University) as part of Geometria em Lisboa (IST)\n
\n\nAbstract\nI will describe two interesting and closely related moduli s
paces: the nilpotent cone in the moduli spaces of Higgs bundles for SL_2(C
) and PSL_2(C)\, and the moduli space of equivariant minimal surfaces in t
he hyperbolic 3-space.\nA deep understanding of these objects is important
because of their relations with several fundamental constructions in geom
etry: singular fibers of the Hitchin fibration\, branes\, mirror symmetry\
, branched hyperbolic structures\, minimal surfaces in hyperbolic 3-manifo
lds and so on.\n\nA stratification of the nilpotent cone is well known and
was rediscovered by many people. The closures of the strata are the irred
ucible components of the nilpotent cone. The talk will focus on describing
the intersections between the different irreducible components.\n\nThis i
s joint work with Qiongling Li and Andrew Sanders\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christine Breiner (Brown University)
DTSTART:20210914T150000Z
DTEND:20210914T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/56
DESCRIPTION:Title: Harmonic branched coverings and uniformization of CAT(k) spheres\nby Christine Breiner (Brown University) as part of Geometria em Lisboa
(IST)\n\n\nAbstract\nConsider a metric space $(S\,d)$ with an upper curvat
ure bound in the sense of Alexandrov (i.e.~via triangle comparison). We sh
ow that if $(S\,d)$ is homeomorphically equivalent to the $2$-sphere\, the
n it is conformally equivalent to the $2$-sphere. The method of proof is t
hrough harmonic maps\, and we show that the conformal equivalence is achie
ved by an almost conformal harmonic map. The proof relies on the analysis
of the local behavior of harmonic maps between surfaces\, and the key step
is to show that an almost conformal harmonic map from a compact surface o
nto a surface with an upper curvature bound is a branched covering. This w
ork is joint with Chikako Mese.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Barbara Fantechi (SISSA)
DTSTART:20210928T153000Z
DTEND:20210928T163000Z
DTSTAMP:20260404T094148Z
UID:Geolis/57
DESCRIPTION:Title: Smoothability of non normal stable Gorenstein Godeaux surfaces\
nby Barbara Fantechi (SISSA) as part of Geometria em Lisboa (IST)\n\n\nAbs
tract\nThis is joint work with Marco Franciosi and Rita Pardini.\n\nGodeau
x surfaces\, with $K^2=1$ and $p_g=q=0$\, are the (complex projective) sur
faces of general type with the smallest possible invariants. A complete cl
assification\, i.e. an understanding of their moduli space\, has been an o
pen problem for many decades.\n\nThe KSBA (after Kollár\, Sheperd-Barron
and Alexeev) compactification of the moduli includes so called stable surf
aces. Franciosi\, Pardini and Rollenske classified all such surfaces in th
e boundary which are Gorenstein (i.e.\, not too singular).\n\nWe prove tha
t most of these surfaces corresponds to a point in the moduli which is non
singular of the expected dimension 8. We expect that the methods used (whi
ch include classical and recent infinitesimal deformation theory\, as well
as algebraic stacks and the cotangent complex) can be applied to all case
s\, and to more general moduli as well.\n\nThe talk is aimed at a non spec
ialist mathematical audience\, and will focus on the less technical aspect
s of the paper.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/57/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Felix Schlenk (Université de Neuchâtel)
DTSTART:20211012T153000Z
DTEND:20211012T163000Z
DTSTAMP:20260404T094148Z
UID:Geolis/58
DESCRIPTION:Title: On the group of symplectomorphisms of starshaped domains\nby Fe
lix Schlenk (Université de Neuchâtel) as part of Geometria em Lisboa (IS
T)\n\n\nAbstract\nTake a simply connected compact domain $K$ in $\\mathbb
R^{2n}$ with smooth boundary. We study the topology of the group $\\mathrm
{Symp} (K)$ of those symplectomorphisms of $K$ that are defined on a neigh
bourhood of $K$. A main tool is a Serre fibration $\\mathrm{Symp} (K) \\to
\\mathrm{SCont} (\\partial K)$ to the group of strict contactomorphisms o
f the boundary. The fiber is contractible if $K$ is 4-dimensional and star
shaped\, by Gromov's theorem. The topology (or at least the connectivity)
of the group $\\mathrm{SCont} (\\partial K)$ can be understood in many exa
mples. In case this group is connected\, so is $\\mathrm{Symp} (K)$. This
has applications to the problem of understanding the topology of the space
of symplectic embeddings of $K$ into any symplectic manifold. If $\\mathr
m{Symp} (K)$ is connected\, then for embeddings that are not related by an
ambient symplectomorphism there is not even an ambient symplectomorphism
that maps one image to the other. \n\nThe talk is based on work with Joé
Brendel and Grisha Mikhalkin.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/58/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pranav Chakravarthy (Hebrew University of Jerusalem)
DTSTART:20211102T163000Z
DTEND:20211102T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/59
DESCRIPTION:Title: Homotopy type of equivariant symplectomorphisms of rational ruled s
urfaces\nby Pranav Chakravarthy (Hebrew University of Jerusalem) as pa
rt of Geometria em Lisboa (IST)\n\n\nAbstract\nIn this talk\, we present r
esults on the homotopy type of the group of equivariant symplectomorphisms
of $S^2 \\times S^2$ and $CP^2$ blown up once\, under the presence of Ham
iltonian group actions of either $S^1$ or finite cyclic groups. For Hamilt
onian circle actions\, we prove that the centralizers are homotopy equival
ent to either a torus or to the homotopy pushout of two tori depending on
whether the circle action extends to a single toric action or to exactly t
wo non-equivalent toric actions. We can show that the same holds for the c
entralizers of most finite cyclic groups in the Hamiltonian group. Our res
ults rely on J-holomorphic techniques\, on Delzant's classification of tor
ic actions\, on Karshon's classification of Hamiltonian circle actions on
4-manifolds\, and on the Chen-Wilczynski smooth classification of $\\mathb
b Z_n$-actions on Hirzebruch surfaces.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/59/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ciprian Manolescu (Standford University)
DTSTART:20211207T163000Z
DTEND:20211207T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/61
DESCRIPTION:Title: Khovanov homology and the search for exotic 4-spheres\nby Cipri
an Manolescu (Standford University) as part of Geometria em Lisboa (IST)\n
\n\nAbstract\nA well-known strategy to disprove the smooth 4D Poincare con
jecture is to find a knot that bounds a disk in a homotopy 4-ball but not
in the standard 4-ball. Freedman\, Gompf\, Morrison and Walker suggested t
hat Rasmussen’s invariant from Khovanov homology could be useful for thi
s purpose. I will describe three recent results about this strategy: that
it fails for Gluck twists (joint work with Marengon\, Sarkar and Willis)\;
that an analogue works for other 4-manifolds (joint work with Marengon an
d Piccirillo)\; and that 0-surgery homeomorphisms provide a large class of
potential examples (joint work with Piccirillo).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/61/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luca Asselle (Ruhr University Bochum)
DTSTART:20211019T153000Z
DTEND:20211019T163000Z
DTSTAMP:20260404T094148Z
UID:Geolis/62
DESCRIPTION:Title: A Morse complex for the Hamiltonian action in cotangent bundles
\nby Luca Asselle (Ruhr University Bochum) as part of Geometria em Lisboa
(IST)\n\n\nAbstract\nCritical points having infinite Morse index and co-in
dex are invisible to homotopy theory\, since attaching an infinite dimensi
onal cell does not produce any change in the topology of sublevel sets. Th
erefore\, no classical Morse theory can possibly exist for strongly indefi
nite functionals (i.e. functionals whose all critical points have infinite
Morse index and co-index). In this talk\, we will briefly explain how to
instead construct a Morse complex for certain classes of strongly indefini
te functionals on a Hilbert manifold by looking at the intersection betwee
n stable and unstable manifolds of critical points whose difference of (su
itably defined) relative indices is one. As a concrete example\, we will c
onsider the case of the Hamiltonian action functional defined by a smooth
time-periodic Hamiltonian $H: S^1 \\times T^*Q \\to \\mathbb R$\, where $T
^*Q$ is the cotangent bundle of a closed manifold $Q$. As one expects\, in
this case the resulting Morse homology is isomorphic to the Floer homolog
y of $T^*Q$\, however the Morse complex approach has several advantages ov
er Floer homology which will be discussed if time permits. This is joint w
ork with Alberto Abbondandolo and Maciej Starostka.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/62/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ely Kerman (University of Illinois Urbana-Champaign)
DTSTART:20211123T163000Z
DTEND:20211123T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/63
DESCRIPTION:Title: On symplectic capacities and their blind spots\nby Ely Kerman (
University of Illinois Urbana-Champaign) as part of Geometria em Lisboa (I
ST)\n\n\nAbstract\nIn this talk I will discuss a joint work with Yuanpu Li
ang in which we establish some results concerning the symplectic capacitie
s defined by Gutt and Hutchings using $S^1$-equivariant symplectic homolog
y. Our primary result settles a version of the recognition question in the
negative. We prove that the Gutt-Hutchings capacities\, together with the
volume\, do not constitute a complete set of symplectic invariants for st
ar-shaped (in fact convex) domains with smooth boundary. We also prove tha
t\, even for star-shaped domains with smooth boundaries\, these capacities
are mutually independent and are independent from the volume. The constru
ctions that demonstrate these independence properties are not exotic. T
hey are convex and concave toric domains. The new tool used here is a sign
ificant simplification of the formulae of Gutt and Hutchings for the capac
ities of convex/concave toric domains\, that holds under an additional sym
metry assumption. This allows us to identify new mutual blind spots of the
capacities which are then used to construct the desired examples.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/63/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Henrique Bursztyn (IMPA)
DTSTART:20211116T163000Z
DTEND:20211116T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/64
DESCRIPTION:Title: Revisiting and extending Poisson-Nijenhuis structures\nby Henri
que Bursztyn (IMPA) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nPo
isson-Nijenhuis structures arise in various settings\, such as the theory
of integrable systems\, Poisson-Lie theory and quantization. By revisitin
g this notion from a new viewpoint\, I will show how it can be naturally e
xtended to the realm of Dirac structures\, with applications to integratio
n results in (holomorphic) Poisson geometry.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/64/
END:VEVENT
BEGIN:VEVENT
SUMMARY:André Neves (University of Chicago)
DTSTART:20211026T153000Z
DTEND:20211026T163000Z
DTSTAMP:20260404T094148Z
UID:Geolis/65
DESCRIPTION:Title: Minimal surfaces in hyperbolic manifolds\nby André Neves (Univ
ersity of Chicago) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nThe
study of geodesics in negatively curved manifolds is a rich subject which
has been at the core of geometry and dynamical systems. Comparatively\, m
uch less is known about minimal surfaces on those spaces. I will survey so
me of the recent progress in that area.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/65/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carlos Florentino (Faculty of Sciences - University of Lisbon)
DTSTART:20211109T163000Z
DTEND:20211109T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/66
DESCRIPTION:Title: The geometry of commuting varieties of reductive groups\nby Car
los Florentino (Faculty of Sciences - University of Lisbon) as part of Geo
metria em Lisboa (IST)\n\n\nAbstract\nLet $R_r(G)$ be the (connected compo
nent of the identity of the) variety of commuting $r$-tuples of elements o
f a complex reductive group $G$. We determine the mixed Hodge structure on
the cohomology of the representation variety $R_r(G)$ and of the characte
r variety $R_r(G)/G$\, for general $r$ and $G$. We also obtain explicit fo
rmulae (both closed and recursive) for the mixed Hodge polynomials\, Poinc
aré polynomials and Euler characteristics of these representation and cha
racter varieties. In the character variety case\, this gives the counting
polynomial over finite fields\, and some results also apply to character v
arieties of nilpotent groups.\n\nThis is joint work with S. Lawton and J.
Silva (arXiv:2110.07060).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/66/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alfonso Zamora (Polytechnic University of Madrid)
DTSTART:20211130T163000Z
DTEND:20211130T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/67
DESCRIPTION:Title: E-polynomials and geometry of character varieties\nby Alfonso Z
amora (Polytechnic University of Madrid) as part of Geometria em Lisboa (I
ST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/67/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hossein Movasati (IMPA)
DTSTART:20220118T163000Z
DTEND:20220118T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/68
DESCRIPTION:Title: A quest for new theories of automorphic forms: Gauss-Manin connecti
on in disguise\nby Hossein Movasati (IMPA) as part of Geometria em Lis
boa (IST)\n\n\nAbstract\nIn this talk I will consider a moduli space of pr
ojective varieties enhanced with a certain frame of its cohomology bundle.
In many examples such as elliptic curves\, abelian varieties and Calabi-Y
au varieties\, and conjecturally in general\, this moduli space is a quasi
-affine variety. There are certain vector fields on this moduli which are
algebraic incarnation of differential equations of automorphic forms. Usin
g these vector fields one can construct foliations with algebraic leaves r
elated to Hodge loci. The talk is based on my book "Modular and Automorphi
c Forms & Beyond\, Monographs in Number Theory\, World Scientific (2021)"
in which the Tupi name ibiporanga (pretty land) for such a moduli space is
suggested.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/68/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lars Sketnan (University of Gothenburg)
DTSTART:20220111T163000Z
DTEND:20220111T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/69
DESCRIPTION:Title: Blowing up extremal Kähler manifolds\nby Lars Sketnan (Univers
ity of Gothenburg) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nExt
remal Kähler metrics were introduced by Calabi in the 80’s as a type of
canonical Kähler metric on a Kähler manifold\, and are a generalisation
of constant scalar curvature Kähler metrics in the case when the manifol
d admits automorphisms. A natural question is when the blowup of a manifol
d in a point admits an extremal Kähler metric. We completely settle the q
uestion in terms of a finite dimensional moment map/GIT condition\, genera
lising work of Arezzo-Pacard\, Arezzo-Pacard-Singer and Székelyhidi. Our
methods also allow us to deal with a certain semistable case that has not
been considered before\, where the original manifold does not admit an ext
remal metric\, but is infinitesimally close to doing so. As a consequence
of this\, we solve the first non-trivial special case of a conjecture of D
onaldson. This is joint work with Ruadhaí Dervan.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/69/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eva Miranda (Universitat Politècnica de Catalunya)
DTSTART:20211221T163000Z
DTEND:20211221T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/70
DESCRIPTION:Title: Looking at the Euler flows through a contact mirror\nby Eva Mir
anda (Universitat Politècnica de Catalunya) as part of Geometria em Lisbo
a (IST)\n\n\nAbstract\nThe dynamics of an inviscid and incompressible flui
d flow on a Riemannian manifold is governed by the Euler equations. Recent
ly\, Tao [6\, 7\, 8] launched a programme to address the global existence
problem for the Euler and Navier-Stokes equations based on the concept of
universality. Inspired by this proposal\, we show that the stationary Eule
r equations exhibit several universality features\, in the sense that\, an
y non-autonomous flow on a compact manifold can be extended to a smooth st
ationary solution of the Euler equations on some Riemannian manifold of po
ssibly higher dimension [1].\n\nA key point in the proof is looking at the
h-principle in contact geometry through a contact mirror\, unveiled by Et
nyre and Ghrist in [4] more than two decades ago. We end this talk address
ing a question raised by Moore in [5] : “Is hydrodynamics capable of per
forming computations?”. The universality result above yields the Turing
completeness of the steady Euler flows on a 17-dimensional sphere. Can thi
s result be improved? In [2] we construct a Turing complete steady Euler f
low in dimension 3. Time permitting\, we discuss this and other generaliza
tions for t-dependent Euler flows contained in [3].\n\nIn all the construc
tions above\, the metric is seen as an additional "variable" and thus the
method of proof does not work if the metric is prescribed.\n\nIs it still
possible to construct a Turing complete Euler flow on a 3-dimensional spac
e with the standard metric? Yes\, see our recent preprint https://arxiv.or
g/abs/2111.03559 (joint with Cardona and Peralta).\n\nThis talk is based o
n several joint works with Cardona\, Peralta-Salas and Presas.\n\n[1] R. C
ardona\, E. Miranda\, D. Peralta-Salas\, F. Presas. Universality of Euler
flows and flexibility of Reeb embeddings\, arXiv:1911.01963.\n\n[2] R. Car
dona\, E. Miranda\, D. Peralta-Salas\, F. Presas. Constructing Turing comp
lete Euler flows in dimension 3. PNAS May 11\, 2021 118 (19) e2026818118\;
https://doi.org/10.1073/pnas.2026818118.\n\n[3] R. Cardona\, E. Miranda a
nd D. Peralta-Salas\, Turing universality of the incompressible Euler equa
tions and a conjecture of Moore\, International Mathematics Research Notic
es\, rnab233\, https://doi.org/10.1093/imrn/rnab233\n\n[4] J. Etnyre\, R.
Ghrist. Contact topology and hydrodynamics I. Beltrami fields and the Seif
ert conjecture. Nonlinearity 13 (2000) 441–458.\n\n[5] C. Moore. General
ized shifts: unpredictability and undecidability in dynamical systems. Non
linearity 4 (1991) 199–230.\n\n[6] T. Tao. On the universality of potent
ial well dynamics. Dyn. PDE 14 (2017) 219–238.\n\n[7] T. Tao. On the uni
versality of the incompressible Euler equation on compact manifolds. Discr
ete Cont. Dyn. Sys. A 38 (2018) 1553–1565.\n\n[8] T. Tao. Searching for
singularities in the Navier-Stokes equations. Nature Rev. Phys. 1 (2019) 4
18–419.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/70/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jonny Evans (University of Lancaster)
DTSTART:20220208T163000Z
DTEND:20220208T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/71
DESCRIPTION:Title: Symplectic cohomology of compound Du Val singularities\nby Jonn
y Evans (University of Lancaster) as part of Geometria em Lisboa (IST)\n\n
\nAbstract\n(Joint with Y. Lekili) If someone gives you a variety with a s
ingular point\, you can try and get some understanding of what the singula
rity looks like by taking its “link”\, that is you take the boundary o
f a neighbourhood of the singular point. For example\, the link of the com
plex plane curve with a cusp y^2 = x^3 is a trefoil knot in the 3-sphere.
I want to talk about the links of a class of 3-fold singularities which co
me up in Mori theory: the compound Du Val (cDV) singularities. These links
are 5-dimensional manifolds. It turns out that many cDV singularities hav
e the same 5-manifold as their link\, and to tell them apart you need to k
eep track of some extra structure (a contact structure). We use symplectic
cohomology to distinguish the contact structures on many of these links.\
n
LOCATION:https://stable.researchseminars.org/talk/Geolis/71/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Johannes Horn (Johann Wolfgang Goethe-Universität in Frankfurt)
DTSTART:20220201T163000Z
DTEND:20220201T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/72
DESCRIPTION:Title: Resolving the rank 2 Hitchin system by compactified Jacobians of se
mi-stable curves\nby Johannes Horn (Johann Wolfgang Goethe-Universitä
t in Frankfurt) as part of Geometria em Lisboa (IST)\n\n\nAbstract\n(joint
work with M. Möller) The complexity of singular fibers of the Hitchin sy
stem stems from the variety of singularities of the spectral curve. In thi
s talk I will explain how to modify the rank 2 Hitchin base\, such that th
e family of spectral curves can be resolved to a family of semi-stable nod
al curves. This allows to extend the Hitchin system to the singular locus
of the modified Hitchin base by well-understood compactified Jacobians of
semi-stable curves\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/72/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giancarlo Urzua (Pontificia Universidad Católica de Chile)
DTSTART:20220125T163000Z
DTEND:20220125T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/74
DESCRIPTION:Title: What is the right combinatorics for spheres in K3 surfaces?\nby
Giancarlo Urzua (Pontificia Universidad Católica de Chile) as part of Ge
ometria em Lisboa (IST)\n\n\nAbstract\nTogether with Javier Reyes\, in htt
ps://arxiv.org/abs/2110.10629 we have been able to construct compact 4-man
ifolds $3\\mathbb{CP}^2\\#(19-K^2)\\overline{\\mathbb{CP}}^2$ with complex
structures for $K^2=1\,2\,3\,4\,5\,6\,7\,8\,9$. The cases $K^2=7\,9$ are
completely new in the literature\, and this finishes with the whole range
allowed by the technique of Q-Gorenstein smoothing (rational blow-down). B
ut one can go further: Is it possible to find minimal exotic $3\\mathbb{CP
}^2\\#(19-K^2)\\overline{\\mathbb{CP}}^2$ for $K^2\\geq10$? Here it would
be much harder to prove the existence of complex structures\, but\, as a m
otivation\, there is not even one example for $K^2 > 15$\, and very few fo
r $10 \\leq K^2 \\leq 15$ (see e.g. works by Akhmedov\, Park\, Baykur). In
this talk I will explain the constructions in connection with the geograp
hy of spheres arrangements in $K3$ surfaces\, where the question of the ti
tle arises. We do not have an answer. So far we have been implementing wha
t we know in computer searches\, finding these very rare exotic surfaces f
or $K^2=10\,11\,12$. This is a new and huge world which promises more find
ings\, we have explored very little.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/74/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Louis Ioos (Max Planck Institute for Mathematics (Bonn))
DTSTART:20220222T163000Z
DTEND:20220222T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/75
DESCRIPTION:Title: Berezin-Toeplitz quantization in the Yau-Tian-Donaldson program
\nby Louis Ioos (Max Planck Institute for Mathematics (Bonn)) as part of G
eometria em Lisboa (IST)\n\n\nAbstract\nA celebrated conjecture of Yau sta
tes that the existence of a Kähler metric of constant scalar curvature on
a projective manifold should be equivalent to a purely algebraic stabilit
y condition. Much progress have been done on this conjecture\, which culmi
nated in what is now called the Yau-Tian-Donaldson program. In this talk\,
I will explain the key role played by quantization methods in this progra
m\, and how they can be improved by a semiclassical study of the quantum n
oise of Berezin-Toeplitz quantization.\nThis is partly based on joint work
s in collaboration with Victoria Kaminker\, Leonid Polterovich and Dor Shm
oish.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/75/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Richard Hind (University of Notre Dame)
DTSTART:20220215T163000Z
DTEND:20220215T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/76
DESCRIPTION:Title: The Gromov width of Lagrangian complements\nby Richard Hind (Un
iversity of Notre Dame) as part of Geometria em Lisboa (IST)\n\n\nAbstract
\nQuestions can be motivated from dynamical systems about the size of comp
lements of a disjoint collection of Lagrangian tori in a symplectic manifo
ld. We will discuss the simplest case\, namely the complement of the integ
ral product Lagrangians\, $L(k\,l)$ with $k\,l \\in \\mathbb{N}$\, inside
$\\mathbb{C}^2$. Here $L(k\,l) = \\{ |z_1| = k\, |z_2|=l \\}$. We will mak
e some computations of the Gromov width and then describe joint work with
Ely Kerman on the existence of Lagrangian tori in the complement.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/76/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joel Fine (Université Libre de Bruxelles)
DTSTART:20220315T163000Z
DTEND:20220315T173000Z
DTSTAMP:20260404T094148Z
UID:Geolis/77
DESCRIPTION:Title: Knots\, minimal surfaces and J-holomorphic curves\nby Joel Fine
(Université Libre de Bruxelles) as part of Geometria em Lisboa (IST)\n\n
\nAbstract\nLet K be a knot in the 3-sphere. I will explain how one can co
unt minimal discs in hyperbolic 4-space which have ideal boundary equal to
K\, and in this way obtain a knot invariant. In other words the number of
minimal discs depends only on the isotopy class of the knot. I think it s
hould actually be possible to define a family of link invariants\, countin
g minimal surfaces filling links\, but at this stage this is still just a
conjecture. “Counting minimal surfaces” needs to be interpreted carefu
lly here\, similar to how Gromov-Witten invariants “count” J-holomorph
ic curves. Indeed I will explain how these counts of minimal discs can be
seen as Gromov-Witten invariants for the twistor space of hyperbolic 4-spa
ce. Whilst Gromov-Witten theory suggests the overall strategy for defining
the minimal surface link-invariant\, there are significant differences in
how to actually implement it. This is because the geometry of both hyperb
olic space and its twistor space become singular at infinity. As a consequ
ence\, the PDEs involved (both the minimal surface equation and J-holomorp
hic curve equation) are degenerate rather than elliptic at the boundary. I
will try and explain how to overcome these complications.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/77/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ana Peón-Nieto (University of Birmingham)
DTSTART:20220308T160000Z
DTEND:20220308T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/78
DESCRIPTION:Title: Higher wobbly bundles\nby Ana Peón-Nieto (University of Birmin
gham) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nWobbly bundles a
re the complement to very stable bundles\, a dense open set of the moduli
space of vector bundles. This notion was generalised to arbitrary fixed po
ints of the C* action on the moduli space of Higgs bundles by Hausel and H
itchin. In this talk\, after introducing the meaningful notions and motiva
ting them\, I will analyse the geometry of higher wobbly components in ran
k three. In particular\, I will focus on an extension of Drinfeld's conjec
ture about pure codimensionality of the wobbly locus\, as well as the rela
tion with real forms. This is joint work with Pauly.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/78/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christian Pauly (Université de Nice Sophia-Antipolis)
DTSTART:20220405T150000Z
DTEND:20220405T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/79
DESCRIPTION:Title: On very stable bundles\nby Christian Pauly (Université de Nice
Sophia-Antipolis) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nA v
ery stable vector bundle over a curve is a vector bundle having no non-zer
o nilpotent Higgs fields. They were introduced by Drinfeld and studied by
Laumon in connection with the nilpotent cone of the Hitchin system. Accord
ing to Drinfeld non-very stable bundles\, also called wobbly bundles\, for
m a divisor in the moduli space of vector bundles. In this talk I will try
to explain the motivations for studying the properties of wobbly divisors
\, with a special focus on the rank-2 (joint work with S. Pal) and rank-3
case (joint work with A. Peon-Nieto).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/79/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michael R. Douglas (Simons Center for Geometry and Physics)
DTSTART:20220412T150000Z
DTEND:20220412T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/80
DESCRIPTION:Title: Holomorphic feedforward networks\nby Michael R. Douglas (Simons
Center for Geometry and Physics) as part of Geometria em Lisboa (IST)\n\n
\nAbstract\nA very popular model in machine learning is the feedforward ne
ural network (FFN). After a brief introduction to machine learning\, we de
scribe FFNs which represent sections of holomorphic line bundles on comple
x manifolds\, and software which uses them to get numerical approximations
to Ricci flat Kähler metrics.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/80/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yang Zhou (Shanghai Center for Mathematical Sciences\, Fudan Unive
rsity)
DTSTART:20220322T100000Z
DTEND:20220322T110000Z
DTSTAMP:20260404T094148Z
UID:Geolis/81
DESCRIPTION:Title: Quasimap wall-crossing in enumerative geometry\nby Yang Zhou (S
hanghai Center for Mathematical Sciences\, Fudan University) as part of Ge
ometria em Lisboa (IST)\n\n\nAbstract\nThe theory of Gromov-Witten invaria
nts is a curve counting theory defined by integration on the moduli of sta
ble maps. Varying the stability condition gives alternative compactificati
ons of the moduli space and defines similar invariants. One example is eps
ilon-stable quasimaps\, defined for a large class of GIT quotients. When e
psilon tends to infinity\, one recovers Gromov-Witten invariants. When eps
ilon tends to zero\, the invariants are closely related to the B-model in
physics. The space of epsilon's has a wall-and-chamber structure. In this
talk\, I will explain how wall-crossing helps to compute the Gromov-Witten
invariants and sketch a proof of the wall-crossing formula.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/81/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jun Li (University of Michigan-Ann Arbor)
DTSTART:20220329T150000Z
DTEND:20220329T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/82
DESCRIPTION:Title: Stability and isotopy of symplectomorphism groups of ruled surfaces
\nby Jun Li (University of Michigan-Ann Arbor) as part of Geometria em
Lisboa (IST)\n\n\nAbstract\nThe symplectomorphism groups $Symp(M\, \\omeg
a)$ of ruled surfaces have been started by Gromov\, McDuff\, and Abreu\, e
tc\, using J-holomorphic techniques. For rational ruled surfaces\, the top
ological structure of $Symp(M\, \\omega)$ is better understood\, while for
irrational cases our only knowledge is for minimal ruled surfaces. In thi
s talk\, we apply the J-inflation techniques of Anjos-Li-Li-Pinsonnault to
irrational non-minimal ruled surfaces and prove a stability result for $S
ymp(M\, \\omega)$. As an application\, we find symplectic mapping classes
that are smoothly but not symplectically isotopic to identity. The talk is
based on joint works with Olguta Buse.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/82/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Miguel Abreu (Instituto Superior Técnico - University of Lisbon)
DTSTART:20220510T150000Z
DTEND:20220510T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/83
DESCRIPTION:Title: Contact invariants of Q-Gorenstein toric contact manifolds and the
Ehrhart (quasi-) polynomials of their toric diagrams\nby Miguel Abreu
(Instituto Superior Técnico - University of Lisbon) as part of Geometria
em Lisboa (IST)\n\n\nAbstract\nQ-Gorenstein toric contact manifolds provid
e an interesting class of examples of contact manifolds with torsion first
Chern class. They are completely determined by certain rational convex po
lytopes\, called toric diagrams. The main goal of this talk is to describe
how the cylindrical contact homology invariants of a Q-Gorenstein toric c
ontact manifold are related to the Ehrhart (quasi-)polynomial of its toric
diagram. This is part of joint work with Leonardo Macarini and Miguel Mor
eira (arXiv:2202.00442).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/83/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vincent Humilière (Institut de Mathématiques de Jussieu - Paris
Rive Gauche)
DTSTART:20220517T150000Z
DTEND:20220517T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/84
DESCRIPTION:Title: Groups of area preserving homeomorphisms and their simplicity\n
by Vincent Humilière (Institut de Mathématiques de Jussieu - Paris Rive
Gauche) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nAlbert Fathi p
roved in the late 70's that the group of volume preserving homeomorphisms
of the n-sphere is simple for n at least 3\, but the case of the 2-sphere
remained open until recently. In this talk\, I will present results obtain
ed in several works with Dan Cristofaro-Gardiner\, Cheuk-Yu Mak\, Sobhan S
eyfaddini and Ivan Smith on the structure of the group of area preserving
homeomorphisms of surfaces\, which include in particular a solution of thi
s problem. Even if the considered objects are not smooth (they are just ho
meomorphisms)\, the tools we use come from symplectic topology.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/84/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Miguel Pereira (University of Augsburg)
DTSTART:20220419T150000Z
DTEND:20220419T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/85
DESCRIPTION:Title: The Lagrangian capacity of toric domains\nby Miguel Pereira (Un
iversity of Augsburg) as part of Geometria em Lisboa (IST)\n\n\nAbstract\n
A symplectic capacity is a functor that to each symplectic manifold (possi
bly in a restricted subclass) assigns a nonnegative number. The Lagrangian
capacity is an example of such an object. In this talk\, I will state a c
onjecture concerning the Lagrangian capacity of a toric domain. Then\, I w
ill present two results concerning this conjecture. First\, I will explain
a proof of the conjecture in the case where the toric domain is convex an
d 4-dimensional. This proof makes use of the Gutt-Hutchings capacities as
well as the McDuff-Siegel capacities. Second\, I will explain a proof of t
he conjecture in full generality\, but assuming the existence of a suitabl
e virtual perturbation scheme which defines the curve counts of linearized
contact homology. This second proof makes use of Siegel's higher symplect
ic capacities.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/85/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lucas Ambrozio (IMPA)
DTSTART:20220426T150000Z
DTEND:20220426T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/86
DESCRIPTION:Title: Analogues of Zoll surfaces in minimal surface theory\nby Lucas
Ambrozio (IMPA) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nA Riem
annian metric on a closed manifold is called Zoll when all of its geodesic
s are closed and have the same period. An infinite dimensional family of Z
oll metrics on the two-dimensional sphere were constructed by Otto Zoll in
the beginning of 1900's\, but many questions about them remain unanswered
. In this talk\, I will explain my motivation to look for higher dimension
al analogues of Zoll metrics\, where closed geodesics are replaced by embe
dded minimal spheres of codimension one. Then\, I will discuss some recent
results about the construction and geometric understanding of these new g
eometries. This is a joint project with F. Marques (Princeton) and A. Neve
s (UChicago).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/86/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gleb Smirnov (University of Geneve)
DTSTART:20220524T150000Z
DTEND:20220524T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/87
DESCRIPTION:Title: Symplectic mapping class groups of K3 surfaces and gauge theory
\nby Gleb Smirnov (University of Geneve) as part of Geometria em Lisboa (I
ST)\n\n\nAbstract\nWe will discuss a simple proof that the symplectic mapp
ing class groups of many K3s are infinitely generated\, extending a recent
result of Sheridan and Smith. The argument will be based on some basic fa
mily Seiberg-Witten theory and algebraic geometry.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/87/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vinicius Ramos (Instituto de Matemática Pura e Aplicada)
DTSTART:20220607T150000Z
DTEND:20220607T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/88
DESCRIPTION:Title: The Toda lattice and the Viterbo conjecture\nby Vinicius Ramos
(Instituto de Matemática Pura e Aplicada) as part of Geometria em Lisboa
(IST)\n\n\nAbstract\nThe Toda lattice is one of the earliest examples of n
on-linear completely integrable systems. Under a large deformation\, the H
amiltonian flow can be seen to converge to a billiard flow in a simplex. I
n the 1970s\, action-angle coordinates were computed for the standard syst
em using a non-canonical transformation and some spectral theory. In this
talk\, I will explain how to adapt these coordinates to the situation to a
large deformation and how this leads to new examples of symplectomorphism
s of Lagrangian products with toric domains. In particular\, we find a seq
uence of Lagrangian products whose symplectic systolic ratio is one and we
prove that they are symplectomorphic to balls. This is joint work with Y.
Ostrover and D. Sepe.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/88/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michael Albanese (Université du Québec à Montréal)
DTSTART:20220614T150000Z
DTEND:20220614T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/89
DESCRIPTION:Title: The Yamabe Invariant of Complex Surfaces\nby Michael Albanese (
Université du Québec à Montréal) as part of Geometria em Lisboa (IST)\
n\n\nAbstract\nThe Yamabe invariant is a real-valued diffeomorphism invari
ant coming from Riemannian geometry. Using Seiberg-Witten theory\, LeBrun
showed that the sign of the Yamabe invariant of a Kähler surface is deter
mined by its Kodaira dimension. We consider the extent to which this remai
ns true when the Kähler hypothesis is removed. This is joint work with Cl
aude LeBrun.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/89/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aleksandar Milivojevic (Max Planck Institute for Mathematics - Bon
n)
DTSTART:20220621T150000Z
DTEND:20220621T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/90
DESCRIPTION:Title: Holomorphic notions of formality and Massey products\nby Aleksa
ndar Milivojevic (Max Planck Institute for Mathematics - Bonn) as part of
Geometria em Lisboa (IST)\n\n\nAbstract\nI will discuss joint work with Jo
nas Stelzig in which we consider the beginnings of a bigraded analogue of
rational homotopy theory adapted to complex manifolds\, in a somewhat diff
erent fashion than that of Neisendorfer-Taylor which appeared in the 1970
’s soon after Sullivan’s Infinitesimal Computations in Topology. Takin
g cues from an additive decomposition theorem for double complexes\, we de
fine two natural notions of formality for our basic objects — commutativ
e bigraded bidifferential algebras — which place both bigraded component
s of the de Rham differential on equal footing. These notions are related
by the ddbar-lemma (the additive property used to show formality\, in the
usual sense\, of compact complex manifolds admitting a Kähler metric). We
consider obstructions to these notions of formality\, taking in Bott-Cher
n cohomology classes and outputting classes in a chain complex of Demailly
-Schweitzer\, whose construction mimics those of classical Massey products
and extends the triple products landing in Aeppli cohomology considered b
y Angella-Tomassini\; we also touch upon their behavior under blow-ups and
more generally positive-degree holomorphic maps.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/90/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bruno de Oliveira (University of Miami)
DTSTART:20220705T150000Z
DTEND:20220705T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/91
DESCRIPTION:Title: $A_n$ singularities and bigness of the cotangent bundle\nby Bru
no de Oliveira (University of Miami) as part of Geometria em Lisboa (IST)\
n\n\nAbstract\nIt is well known that for surfaces the positivity property
of the cotangent bundle $\\Omega^1_X$ called bigness implies hyperbolic pr
operties. We give a criterion for bigness of $\\Omega^1_X$ involving the s
ingularities of the canonical model of $X$ and compare it with other crite
rions. The criterion involves invariants of the canonical singularities wh
ose values were unknown. We describe a method to find the invariants and o
btain formulas for the $A_n$ singularities. An application of this work is
to determine for which degrees do hypersurfaces in $\\mathbb {P}^3$ have
deformations with big cotangent bundles and have symmetric differentials o
f low degrees.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/91/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexander Givental (University of Berkeley)
DTSTART:20220916T150000Z
DTEND:20220916T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/92
DESCRIPTION:Title: K-theoretic Gromov-Witten invariants and their adelic characterizat
ion\nby Alexander Givental (University of Berkeley) as part of Geometr
ia em Lisboa (IST)\n\n\nAbstract\nGromov-Witten invariants of a given Kahl
er target space are defined as suitable intersection numbers in moduli spa
ces of stable maps of complex curves into the target space. Their K-theore
tic analogues are defined as holomorphic Euler characteristics of suitable
vector bundles over these moduli spaces.\nWe will describe how the Kawasa
ki-Riemann-Roch theorem expressing holomorphic Euler characteristics in co
homological terms leads to the adelic formulas for generating functions en
coding K-theoretic Gromov-Witten invariants.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/92/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Inder Kaur (Goethe University Frankfurt am Main)
DTSTART:20220531T150000Z
DTEND:20220531T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/93
DESCRIPTION:Title: Birational geometry of blow-ups of projective spaces\nby Inder
Kaur (Goethe University Frankfurt am Main) as part of Geometria em Lisboa
(IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/93/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simon Jubert (Université du Québec à Montréal)
DTSTART:20221108T160000Z
DTEND:20221108T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/94
DESCRIPTION:Title: A Yau-Tian-Donaldson correspondence on a class of toric fibration\nby Simon Jubert (Université du Québec à Montréal) as part of Geome
tria em Lisboa (IST)\n\n\nAbstract\nThe Yau-Tian-Donaldson (YTD) conjectur
e predicts that the existence of an extremal metric (in the sense of Calab
i) in a given Kahler class of Kahler manifold is equivalent to a certain a
lgebro-geometric notion of stability of this class. In this talk\, we will
discuss the resolution of this conjecture for a certain class of toric fi
brations\, called semisimple principal toric fibrations. After an introduc
tion to the Calabi Problem for general Kahler manifolds\, we will focus on
the toric setting. Then we will see how to reduce the Calabi problem on t
he total space of a semisimple principal toric fibration to a weighted con
stant scalar curvature K\\"ahler problem on the toric fibers. If the time
allows\, I will give elements of proof.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/94/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matias del Hoyo (Universidade Federal Fluminense)
DTSTART:20221115T160000Z
DTEND:20221115T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/95
DESCRIPTION:Title: Completeness of metrics and linearization of Lie groupoids\nby
Matias del Hoyo (Universidade Federal Fluminense) as part of Geometria em
Lisboa (IST)\n\n\nAbstract\nEvery smooth fiber bundle admits a complete Eh
resmann connection. I will talk about the story of this theorem and its re
lation with Riemannian submersions. Then\, after discussing some foundatio
ns of Riemannian geometry of Lie groupoids and stacks\, I will present a g
eneralization of the theorem into this framework\, which somehow answers a
n open problem on linearization. Talk based on collaborations with my form
er student M. de Melo.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/95/
END:VEVENT
BEGIN:VEVENT
SUMMARY:João Pimentel Nunes (Instituto Superior Técnico)
DTSTART:20221122T160000Z
DTEND:20221122T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/96
DESCRIPTION:Title: The geometric interpretation of the Peter-Weyl theorem\nby Joã
o Pimentel Nunes (Instituto Superior Técnico) as part of Geometria em Lis
boa (IST)\n\n\nAbstract\nLet $K$ be a compact Lie group. I will review the
construction of Mabuchi geodesic families of $K\\times K-$invariant Kahle
r structures on $T^*K$\, via Hamiltonian flows in imaginary time generated
by a strictly convex invariant function on $Lie \\\, K$\, and the corresp
onding geometric quantization. At infinite geodesic time\, one obtains a r
ich mixed polarization of $T^*K$\, the Kirwin-Wu polarization\, which is t
hen continuously connected to the vertical polarization of $T^*K$. The geo
metric quantization of $T^*K$ along this family of polarizations is descri
bed by a generalized coherent state transform that\, as geodesic time goes
to infinity\, describes the convergence of holomorphic sections to distri
butional sections supported on Bohr-Sommerfeld cycles. These are in corres
pondence with coadjoint orbits $O_{\\lambda+\\rho}$. One then obtains a co
ncrete (quantum) geometric interpretation of the Peter-Weyl theorem\, wher
e terms in the non-abelian Fourier series are directly related to geometri
c cycles in $T^*K$. The role of a singular torus action in this constructi
on will also be emphasized. This is joint work with T.Baier\, J. Hilgert\,
O. Kaya and J. Mourão.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/96/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gustavo Granja (Instituto Superior Técnico - Universidade de Lisb
oa)
DTSTART:20221004T150000Z
DTEND:20221004T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/97
DESCRIPTION:Title: Topology of almost complex structures\nby Gustavo Granja (Insti
tuto Superior Técnico - Universidade de Lisboa) as part of Geometria em L
isboa (IST)\n\n\nAbstract\nI will report on joint work in progress with Al
eksandar Milivojevic (MPIM Bonn) on the elementary topology of the space o
f almost complex structures on a manifold. First I will describe a certain
natural parametrization and associated stratification of the space of lin
ear complex structures on a vector space and give a lower bound for the nu
mber of complex k-planes jointly preserved by two linear complex structure
s. Then I will focus on dimension 6 and prove a formula for the homologica
l intersection of two orthogonal almost complex structures on a Riemannian
6-manifold when these are regarded as sections of the twistor space.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/97/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Antonella Grassi (Università di Bologna)
DTSTART:20221011T150000Z
DTEND:20221011T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/98
DESCRIPTION:Title: A family of threefolds with several unusual features\nby Antone
lla Grassi (Università di Bologna) as part of Geometria em Lisboa (IST)\n
\n\nAbstract\nI will discuss some of the unusual properties\, in geometry
and physics\, of a family of Calabi-Yau threefolds fibered by elliptic cur
ves. I will compare it to a construction by Elkies and a classical results
of Burkhardt. This leads to some open questions.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/98/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lino Amorim (Kansas State University)
DTSTART:20220927T150000Z
DTEND:20220927T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/99
DESCRIPTION:Title: From categories to Gromov-Witten invariants\nby Lino Amorim (Ka
nsas State University) as part of Geometria em Lisboa (IST)\n\n\nAbstract\
nKontsevich suggested that enumerative predictions of Mirror Symmetry shou
ld follow directly from Homological Mirror Symmetry. This requires a natur
al construction of analogues of Gromov-Witten invariants associated to any
A-infinity Calabi-Yau category\, with some extra choices. I will explain
what these choices are and survey two approaches to this construction\, on
e in genus zero and another (conjectural) in all genera.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/99/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Miguel Moreira (ETH Zurich)
DTSTART:20221018T150000Z
DTEND:20221018T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/100
DESCRIPTION:Title: Virasoro constraints in sheaf theory\nby Miguel Moreira (ETH Z
urich) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nVirasoro constr
aints for Gromov-Witten invariants have a rich history tied to the very be
ginning of the subject\, but recently there have been many developments on
the sheaf side. In this talk I will survey those developments and talk ab
out joint work with A. Bojko and W. Lim where we propose a general conject
ure of Virasoro constraints for moduli spaces of sheaves and formulate it
using the vertex algebra that D. Joyce recently introduced to study wall-c
rossing. Using Joyce's framework we can show compatibility between wall-cr
ossing and the constraints\, which we then use to prove that they hold for
moduli of stable sheaves on curves and surfaces with $h^{0\,1}=h^{0\,2}=0
$. In the talk I will give a rough overview of the vertex algebra story an
d focus on the ideas behind the proof in the case of curves.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/100/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luis Diogo (Uppsala University)
DTSTART:20221220T160000Z
DTEND:20221220T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/101
DESCRIPTION:Title: Lagrangian tori in the cotangent bundle of the 2-sphere\nby Lu
is Diogo (Uppsala University) as part of Geometria em Lisboa (IST)\n\n\nAb
stract\nGiven a symplectic manifold\, one can ask what Lagrangian submanif
olds it contains. I will discuss this question for one of the simplest exa
mples of a non-trivial symplectic manifold\, namely the cotangent bundle o
f the 2-sphere. Specifically\, I will present a result about monotone Lagr
angian tori as objects in the Fukaya category. If time permits\, I will al
so discuss the problem of classifying Lagrangian tori up to Hamiltonian is
otopy.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/101/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sofia Tirabassi (Stockholm University)
DTSTART:20221206T160000Z
DTEND:20221206T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/102
DESCRIPTION:Title: Characterization of quasi-abelian surfaces\nby Sofia Tirabassi
(Stockholm University) as part of Geometria em Lisboa (IST)\n\n\nAbstract
\nWe give an effective characterization of quasi-abelian surfaces extendin
g to the quasi-projective setting results of Enriques and Chen--Hacon. Thi
s is a joint work with M. Mendes Lopes and R. Pardini.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/102/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicki Magill (Cornell University)
DTSTART:20221213T160000Z
DTEND:20221213T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/103
DESCRIPTION:Title: Symplectic embeddings of Hirzebruch surfaces\nby Nicki Magill
(Cornell University) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nT
he four dimensional ellipsoid embedding function of a toric symplectic man
ifold M measures when a symplectic ellipsoid embeds into M. It generalizes
the Gromov width and ball packing numbers. In 2012\, McDuff and Schlenk c
omputed this function for a ball. The function has a delicate structure kn
own as an infinite staircase. This implies infinitely many obstructions ar
e needed to know when an embedding can exist. Based on work with McDuff\,
Pires\, and Weiler\, we will discuss the classification of which Hirzebruc
h surfaces have infinite staircases. We will focus on the part of the argu
ment where symplectic embeddings are constructed via almost toric fibratio
ns.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/103/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sobhan Seyfaddini (Institut de Mathématiques de Jussieu - Paris R
ive Gauche)
DTSTART:20221129T160000Z
DTEND:20221129T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/104
DESCRIPTION:Title: On the algebraic structure of groups of area-preserving homeomorph
isms\nby Sobhan Seyfaddini (Institut de Mathématiques de Jussieu - Pa
ris Rive Gauche) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nIn an
influential article from the 1970s\, Albert Fathi\, having proven that th
e group of compactly supported volume-preserving homeomorphisms of the $n$
-ball is simple for $n\\geq 3$\, asked if the same statement holds in dime
nsion $2$. In a joint work with Cristofaro-Gardiner and Humilière\, we pr
oved that the group of compactly supported area-preserving homeomorphisms
of the $2$-disc is not simple. This answers Fathi's question and settles w
hat is known as "the simplicity conjecture" in the affirmative.\n\nIn fact
\, Fathi posed a more general question about all compact surfaces: is the
group of "Hamiltonian homeomorphisms" (which I will define) simple? In my
talk\, I will review recent joint work with Cristofaro-Gardiner\, Humiliè
re\, Mak and Smith answering this more general question of Fathi. The talk
will be for the most part elementary and will only briefly touch on Floer
homology which is a crucial ingredient of the solution.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/104/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leonardo Macarini (Instituto Superior Técnico\, Universidade de L
isboa)
DTSTART:20230103T160000Z
DTEND:20230103T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/106
DESCRIPTION:Title: Symmetric periodic Reeb orbits on the sphere\nby Leonardo Maca
rini (Instituto Superior Técnico\, Universidade de Lisboa) as part of Geo
metria em Lisboa (IST)\n\n\nAbstract\nA long standing conjecture in Hamilt
onian Dynamics states that every contact form on the standard contact sphe
re $S^{2n+1}$ has at least $n+1$ simple periodic Reeb orbits. In this talk
\, I will consider a refinement of this problem when the contact form has
a suitable symmetry and we ask if there are at least $n+1$ simple symmetri
c periodic orbits. We show that there is at least one symmetric periodic o
rbit for any contact form and at least two symmetric closed orbits wheneve
r the contact form is dynamically convex. This is joint work with Miguel A
breu and Hui Liu.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/106/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stéphanie Cupit-Foutou (Ruhr-Universität Bochum)
DTSTART:20230207T160000Z
DTEND:20230207T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/107
DESCRIPTION:Title: The Gromov width of compact toric manifolds\nby Stéphanie Cup
it-Foutou (Ruhr-Universität Bochum) as part of Geometria em Lisboa (IST)\
n\n\nAbstract\nAfter some basic recalls on the notion of Gromov width of a
symplectic manifold\, I will focus on the case of toric manifolds. I shal
l explain how this symplectic capacity can be estimated and even computed.
This is a joint work with C. Bonala.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/107/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emilio Franco (Universidad Autónoma de Madrid)
DTSTART:20230110T160000Z
DTEND:20230110T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/108
DESCRIPTION:Title: Lagrangians of Hecke cycles in the moduli space of Higgs bundles\nby Emilio Franco (Universidad Autónoma de Madrid) as part of Geometri
a em Lisboa (IST)\n\n\nAbstract\nThe moduli space of Higgs bundles over a
curve is a well known (singular) variety with an extremely rich geometry\,
in particular it is hyperKähler and becomes an integrable system after b
eing equipped with the so called Hitchin morphism which\, to any Higgs bun
dle\, associates a finite cover of the base curve named spectral curve. As
sociated to the hyperKähler structure\, Kapustin and Witten introduced in
2007\, BBB and BAA-branes\, predicting that they occur in pairs dual unde
r mirror symmetry. An example of BBB-brane is a hyperKähler bundle suppor
ted on hyperKähler subvariety\, and an example of BAA-brane is a flat bun
dle supported on a complex Lagrangian subvariety. Hitchin described in 201
9 a family of subintegral systems lying on the critical loci of the Hitchi
n integrable system parametrized by spectral curves with a fixed number of
singularities. The critical subsystem obtained by considering spectral cu
rves with maximal number of singularities is a hyperKähler subvariety and
the author\, along with Oliveira\, Peón-Nieto and Gothen\, studied the B
BB-branes constructed over it\, and their image under Fourier-Mukai transf
orm\, which are supported on complex Lagrangian subvarieties. Surprinsingl
y\, Hitchin showed that the critical subsystem obtained by considering spe
ctral curves with 1 singularity is not a hyperKähler subvariety and he co
njectured that only the critical subsystem with a maximal number of singul
arities is hyperKähler.\n\nIn this work\, joint with Hanson\, Horn and Ol
iveira\, we study the critical subsystems with any number of singularities
\, showing that their image under Fourier-Mukai is supported on a certain
family of complex Lagrangian subvarieties which we describe.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/108/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yaiza Canzani (University of North Carolina at Chapel Hill)
DTSTART:20230117T160000Z
DTEND:20230117T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/109
DESCRIPTION:Title: Counting closed geodesics and improving Weyl’s law for predomina
nt sets of metrics\nby Yaiza Canzani (University of North Carolina at
Chapel Hill) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nWe discus
s the typical behavior of two important quantities on compact manifolds wi
th a Riemannian metric g: the number\, c(T\, g)\, of primitive closed geod
esics of length smaller than T\, and the error\, E(L\, g)\, in the Weyl la
w for counting the number of Laplace eigenvalues that are smaller than L.
For Baire generic metrics\, the qualitative behavior of both of these quan
tities has been understood since the 1970’s and 1980’s. In terms of qu
antitative behavior\, the only available result is due to Contreras and it
says that an exponential lower bound on c(T\, g) holds for g in a Baire-g
eneric set. Until now\, no upper bounds on c(T\, g) or quantitative improv
ements on E(L\, g) were known to hold for most metrics\, not even for a de
nse set of metrics. In this talk\, we will introduce the concept of predom
inance in the space of Riemannian metrics. This is a notion that is analog
ous to having full Lebesgue measure in finite dimensions\, and which\, in
particular\, implies density. We will then give stretched exponential uppe
r bounds for c(T\, g) and logarithmic improvements for E(L\, g) that hold
for a predominant set of metrics. This is based on joint work with J. Galk
owski.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/109/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gonçalo Oliveira (Instituto Superior Técnico\, Universidade de L
isboa)
DTSTART:20230214T160000Z
DTEND:20230214T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/110
DESCRIPTION:Title: From electrostatics to geodesics in K3 surfaces\nby Gonçalo O
liveira (Instituto Superior Técnico\, Universidade de Lisboa) as part of
Geometria em Lisboa (IST)\n\n\nAbstract\nMotivated by some conjectures ori
ginating in the Physics literature\, I have recently been looking for clos
ed geodesics in the K3 surfaces constructed by Lorenzo Foscolo. It turns o
ut to be possible to locate several such with high precision and compute t
heir index (their length is also approximately known). Interestingly\, in
my view\, the construction of these geodesics is related to an open proble
m in electrostatics posed by Maxwell in 1873.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/110/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tiago Guerreiro (University of Essex)
DTSTART:20230228T160000Z
DTEND:20230228T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/111
DESCRIPTION:Title: On the birational geometry of Fano threefold complete intersection
s\nby Tiago Guerreiro (University of Essex) as part of Geometria em Li
sboa (IST)\n\n\nAbstract\nThe Minimal Model Program (MMP) is a far reachin
g conjecture in birational geometry which aims at constructing a good repr
esentative (minimal model) of any given complex projective variety W. When
such a model exists it might not be unique and so it becomes natural to s
tudy the relations between them. In the case when W is covered by rational
curves\, its minimal model is a Mori fibre space\, that is\, a fibration
whose generic fibre is positively curved\, and its uniqueness is encoded i
n the notion of birational rigidity. In this talk we will give an introduc
tion to the ideas of the MMP with the background of Fano threefold complet
e intersections.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/111/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yunhyung Cho (Sungkyunkwan University)
DTSTART:20230119T160000Z
DTEND:20230119T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/112
DESCRIPTION:Title: Monotone Lagrangian tori and Mirror symmetry of Fano varieties
\nby Yunhyung Cho (Sungkyunkwan University) as part of Geometria em Lisboa
(IST)\n\n\nAbstract\nThis is a survey talk of current progress of mirror
symmetry of Fano varieties. For a given smooth Fano variety X\, it has bee
n conjectured that there exists a Laurent polynomial called a (weak) Landa
u-Ginzburg mirror (or weak LG mirror shortly) which encodes a quantum coho
mology ring structure of X. Tonkonog proved that one can find a weak LG mi
rror using a monotone Lagrangian torus in X. In this talk I will explain h
ow to find a monotone Lagrangian torus using a Fano toric degeneration of
X. If time permits\, I will also describe a monotone Lagrangian torus in a
given flag variety.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/112/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vestislav Apostolov (Université du Québec à Montréal)
DTSTART:20230411T150000Z
DTEND:20230411T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/113
DESCRIPTION:Title: A Calabi type problem in generalized Kahler geometry\nby Vesti
slav Apostolov (Université du Québec à Montréal) as part of Geometria
em Lisboa (IST)\n\n\nAbstract\nThe notion of a generalized Kahler (GK) str
ucture was introduced in the early 2000's by Hitchin and Gualtieri in orde
r to provide a mathematically rigorous framework of certain nonlinear sigm
a model theories in physics. Since then\, the subject has developed rapidl
y. It is now realized\, thanks to more recent works of Hitchin\, Goto\, Gu
altieri\, Bischoff and Zabzine\, that GK structures are naturally attached
to Kahler manifolds endowed with a holomorphic Poisson structure. Inspire
d by Calabi's program in Kahler geometry\, which aims at finding a "canoni
cal" Kahler metric in a fixed deRham class\, I will present in this talk a
n approach towards a “generalized Kahler" version of Calabi's problem mo
tivated by an infinite dimensional moment map formalism\, and using the Bi
smut-Ricci flow introduced by Streets and Tian as analytical tool. As an a
pplication\, we give an essentially complete resolution of the problem in
the case of a toric complex Poisson variety. Based on a joint works with J
. Streets and Y. Ustinovskiy.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/113/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ruobing Zhang (Princeton University)
DTSTART:20230307T160000Z
DTEND:20230307T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/114
DESCRIPTION:Title: Degenerations and metric geometry of collapsing Calabi-Yau manifol
ds\nby Ruobing Zhang (Princeton University) as part of Geometria em Li
sboa (IST)\n\n\nAbstract\nWe will give a complete picture of the metric ge
ometry of Calabi-Yau manifolds along degenerations of complex structures\,
which holds for all dimensions. In particular\, we will classify the Gro
mov-Hausdorff limits on all scales\, describe the singularity formation\,
and formulate a more general conjecture. This is based on my joint work wi
th Song Sun (arXiv: 1906.03368).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/114/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Weiwei Wu (Zhejiang University)
DTSTART:20230321T130000Z
DTEND:20230321T140000Z
DTSTAMP:20260404T094148Z
UID:Geolis/115
DESCRIPTION:Title: Symplectic Torelli groups for positive rational surfaces\nby W
eiwei Wu (Zhejiang University) as part of Geometria em Lisboa (IST)\n\n\nA
bstract\nDonaldson (folklore) asked whether Lagrangian Dehn twists always
generate the symplectic mapping class groups in real dimension four. So fa
r\, all known examples indicate this is true\, even though the symplectic
Torelli group is generally much larger than the algebraic one. Yet there a
re only very few cases people could prove this as a theorem.\n\nWe will de
fine a notion of "positive rational surfaces"\, which is equivalent to the
ambient symplectic manifolds of (symplectic) log Calabi-Yau pairs. We com
pute the symplectic Torelli group for the positive rational surfaces and c
onfirm Donaldson's conjecture as a result. We also answer several other qu
estions about the symplectic Torelli groups in dimension $4$.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/115/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Song Sun (University of California\, Berkeley)
DTSTART:20230328T150000Z
DTEND:20230328T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/116
DESCRIPTION:Title: Complete Calabi-Yau metrics asymptotic to cones\nby Song Sun (
University of California\, Berkeley) as part of Geometria em Lisboa (IST)\
n\n\nAbstract\nComplete Calabi-Yau metrics provide singularity models for
limits of Kahler-Einstein metrics. We study complete Calabi-Yau metrics wi
th Euclidean volume growth and quadratic curvature decay. It is known that
under these assumptions the metric is always asymptotic to a unique cone
at infinity. Previous work of Donaldson-S. gives a 2-step degeneration to
the cone in the algebro-geometric sense\, via a possible intermediate obje
ct (a K-semistable cone). We will show that such intermediate K-semistable
cone does not occur. This is in sharp contrast to the case of local singu
larities. This result together with the work of Conlon-Hein also give a co
mplete algebro-geometric classification of these metrics\, which in partic
ular confirms Yau’s compactification conjecture in this setting. I will
explain the proof in this talk\, and if time permits I will describe a con
jectural picture in general when the curvature decay condition is removed.
Based on joint work with Junsheng Zhang (UC Berkeley).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/116/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joé Brendel (School of Mathematical Sciences\, Tel Aviv Universit
y)
DTSTART:20230418T150000Z
DTEND:20230418T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/117
DESCRIPTION:Title: Symmetric probes and classification of toric fibres\nby Joé B
rendel (School of Mathematical Sciences\, Tel Aviv University) as part of
Geometria em Lisboa (IST)\n\n\nAbstract\nToric symplectic manifolds contai
n an interesting and well-studied family of Lagrangian tori\, called toric
fibres. In this talk\, we address the natural question of which toric fib
res are equivalent under Hamiltonian diffeomorphisms of the ambient space.
On one hand\, we use a symmetric version of McDuff's probes to construct
such equivalences and on the other hand\, we give certain obstructions com
ing from Chekanov's classification of product tori in symplectic vector sp
aces combined with a lifting trick from toric geometry. We will discuss ma
ny four-dimensional examples in which a full classification can be achieve
d.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/117/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Umut Varolgunes (Bogazici University)
DTSTART:20230314T160000Z
DTEND:20230314T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/118
DESCRIPTION:Title: Heaviness and SH-visibility\nby Umut Varolgunes (Bogazici Univ
ersity) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nConsider a com
pact subset K of a closed symplectic manifold M. We say that K is SH-visib
le if its relative symplectic cohomology does not vanish over the Novikov
field. With Cheuk Yu Mak and Yuhan Sun\, we recently proved that SH-visibi
lity is equivalent to K being heavy as defined by Entov-Polterovich. l wil
l recall these notions and explain the proof. If time permits I will also
discuss some consequences.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/118/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Claude LeBrun (Stony Brook University)
DTSTART:20230316T153000Z
DTEND:20230316T163000Z
DTSTAMP:20260404T094148Z
UID:Geolis/119
DESCRIPTION:Title: Einstein Manifolds\, Self-Dual Weyl Curvature\, and Conformally K
ähler Geometry\nby Claude LeBrun (Stony Brook University) as part of
Geometria em Lisboa (IST)\n\n\nAbstract\nThere are certain compact 4-manif
olds\, such as real and complex hyperbolic 4-manifolds\, 4-tori\, and K3\,
where we completely understand the moduli space of Einstein metrics. But
there are vast numbers of other 4-manifolds where we know that Einstein me
trics exist\, but cannot currently determine whether or not there might al
so exist other Einstein metrics on them that are utterly different from th
e ones we currently know.\n\nIn this lecture\, I will present two quite di
fferent characterizations of the known Einstein metrics on del Pezzo surfa
ces. These results imply\, in particular\, that the known Einstein metrics
exactly sweep out a single connected component of the Einstein moduli spa
ce. I will then briefly indicate the role these results play in current av
enues of research.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/119/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Žan Grad (Instituto Superior Técnico)
DTSTART:20230509T150000Z
DTEND:20230509T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/120
DESCRIPTION:Title: Lie categories\nby Žan Grad (Instituto Superior Técnico) as
part of Geometria em Lisboa (IST)\n\n\nAbstract\nWhat does it mean for a c
ategory to be endowed with a compatible differentiable structure? In this
talk\, we will discuss the interplay of a categorical structure with that
of a smooth manifold\, and show how to describe such categories infinitesi
mally\, similarly as to how we construct the Lie algebra of a Lie group. W
e will generalise the notion of rank from linear algebra to morphisms of L
ie categories\, and introduce the notion of an extension of a Lie category
to a groupoid. Examples of Lie categories arising in differential geometr
y and in physics will be highlighted.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/120/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jörg Teschner (DESY\, Theory Group)
DTSTART:20230516T150000Z
DTEND:20230516T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/121
DESCRIPTION:Title: Separation of variables and analytic Langlands correspondence\
nby Jörg Teschner (DESY\, Theory Group) as part of Geometria em Lisboa (I
ST)\n\n\nAbstract\nFamous results of N. Hitchin establish existence of an
integrable structure of the Hitchin moduli spaces. The goal of this talk w
ill be to discuss a more explicit approach known in the integrable models
literature as separation of variables\, how it can be applied to the quant
isation of the Hitchin system\, and how the result is related to the analy
tic Langlands correspondence studied by Etingof\, Frenkel and Kazhdan.\n\n
Partly based on arXiv:1707.07873\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/121/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Valery Alexeev (University of Georgia)
DTSTART:20230516T133000Z
DTEND:20230516T143000Z
DTSTAMP:20260404T094148Z
UID:Geolis/122
DESCRIPTION:Title: Compact moduli of K3 surfaces and tropical spheres with 24 singula
r points\nby Valery Alexeev (University of Georgia) as part of Geometr
ia em Lisboa (IST)\n\n\nAbstract\nI will talk about geometric compactifica
tions of moduli spaces of K3 surfaces\, similar in spirit to the Deligne-M
umford moduli spaces of stable curves. Constructions borrow ideas from the
tropical and integral-affine geometry and mirror symmetry. The main resul
t is that in many common situations there exists a geometric compactificat
ion which is toroidal\, and many of these compactifications can be describ
ed explicitly using tropical spheres with 24 singular points. Much of this
talk is based on the joint work with Philip Engel.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/122/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bruno de Oliveira (University of Miami)
DTSTART:20230620T150000Z
DTEND:20230620T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/123
DESCRIPTION:Title: On the geography of surfaces with big cotangent bundle\nby Bru
no de Oliveira (University of Miami) as part of Geometria em Lisboa (IST)\
n\n\nAbstract\nBigness of the cotangent bundle is a negativity property of
the curvature which has important complex analytic consequences\, such as
on the Kobayashi hyperbolicity properties and the GGL-conjecture for surf
aces. We present a birational criterion for a surface to have big cotangen
t bundle that takes in account the singularities present in the minimal mo
del and describe how it improves upon other criterions. The criterion allo
ws certain geographic regions of surfaces of general type to have big cota
ngent bundle\, that other criterions can not reach. In this spirit\, we pr
oduce the examples with the lowest slope $c_1^2/c_2$ having big cotangent
bundle that are currently known.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/123/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex Waldron (University of Wisconsin - Madison)
DTSTART:20230606T150000Z
DTEND:20230606T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/124
DESCRIPTION:Title: Strong gap theorems via Yang-Mills flow\nby Alex Waldron (Univ
ersity of Wisconsin - Madison) as part of Geometria em Lisboa (IST)\n\n\nA
bstract\nGiven a principal bundle over a compact Riemannian 4-manifold or
special-holonomy manifold\, it is natural to ask whether a uniform gap exi
sts between the instanton energy and that of any non-minimal Yang-Mills co
nnection. This question is quite open in general\, although positive resul
ts exist in the literature. We'll review several of these gap theorems and
strengthen them to statements of the following type: the space of all con
nections below a certain energy deformation retracts (under Yang-Mills flo
w) onto the space of instantons. As applications\, we recover a theorem of
Taubes on path-connectedness of instanton moduli spaces on the 4-sphere\,
and obtain a method to construct instantons on quaternion-Kähler manifol
ds with positive scalar curvature.\n\nThe talk is based on joint work in p
rogress with Anuk Dayaprema (UW-Madison).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/124/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Brayan Ferreira (Universidade Federal do Espírito Santo)
DTSTART:20231003T150000Z
DTEND:20231003T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/125
DESCRIPTION:Title: Symplectic embeddings into disk cotangent bundles of spheres\n
by Brayan Ferreira (Universidade Federal do Espírito Santo) as part of Ge
ometria em Lisboa (IST)\n\n\nAbstract\nThe question whether a symplectic m
anifold embeds into another is central in symplectic topology. Since Gromo
v nonsqueezing theorem\, it is known that this is a different problem from
volume preserving embedding. There are several nice results about symplec
tic embeddings between open subsets of $\\mathbb R^{2n}$ showing that even
for those examples the question can be completely nontrivial. The problem
is substantially more well understood when the manifolds are toric domain
s and have dimension $4$\, mostly because of obstructions coming from embe
dded contact homology (ECH). In this talk we are going to discuss symplect
ic embedding problems in which the target manifold is the disk cotangent b
undle of a two-dimensional sphere\, i.e.\, the set consisting of the covec
tors with norm less than $1$ over a Riemannian sphere. We shall talk about
some tools such as ECH capacities and action angle coordinates. Much of t
his talk is based on joint works with Vinicius Ramos and Alejandro Vicente
.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/125/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Manuel Krannich (Karlsruhe Institute of Technology)
DTSTART:20231010T150000Z
DTEND:20231010T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/126
DESCRIPTION:Title: Exotic tori\, actions by $\\mathrm{SL}_d(\\mathbb Z)$\, and mappin
g class groups\nby Manuel Krannich (Karlsruhe Institute of Technology)
as part of Geometria em Lisboa (IST)\n\n\nAbstract\nOne of the distinctiv
e feature of the $d$-dimensional torus $T^d$ is that it admits a faithful
smooth action by $\\mathrm{SL}_d(\\mathbb Z)$\, so one might wonder whethe
r such an action (or any nontrivial action) also exists for exotic tori i.
e. smooth $d$-manifolds that are homeomorphic but not diffeomorphic to $T^
d$. I will discuss this and related questions in the talk\, based on joint
work with M. Bustamante\, A. Kupers\, and B. Tshishiku.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/126/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Martin Pinsonnault (University of Western Ontario)
DTSTART:20231017T150000Z
DTEND:20231017T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/127
DESCRIPTION:Title: Embeddings of symplectic balls in $\\mathbb{C}P^2$ and configurati
on spaces\nby Martin Pinsonnault (University of Western Ontario) as pa
rt of Geometria em Lisboa (IST)\n\n\nAbstract\nExistence of symplectic emb
eddings of $k$ disjoint balls of given capacites $c_1\,\\ldots\, c_k$ into
a given symplectic manifold is a central problem in symplectic topology.
However\, beside a few examples\, very little is known about the space of
all such embeddings. In this talk\, I will discuss the case of rational $4
$-manifolds of small Euler numbers\, with a special attention to the minim
al manifolds $\\mathbb{C}P^2$ and $S^2\\times S^2$. For rational manifolds
\, a very rich and intricate picture emerges that blends symplectic topolo
gy\, complex geometry\, and algebraic topology.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/127/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carlos Florentino (Faculdade de Ciências da Universidade de Lisbo
a)
DTSTART:20230926T150000Z
DTEND:20230926T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/128
DESCRIPTION:Title: Symplectic resolutions of moduli spaces of G-Higgs bundles over ab
elian varieties\nby Carlos Florentino (Faculdade de Ciências da Unive
rsidade de Lisboa) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nFol
lowing A. Beauville\, a complex algebraic variety $X$ is said to be symple
ctic if it admits a holomorphic symplectic form $\\omega$ on its smooth lo
cus such that\, for every resolution $\\pi: Y \\to X$\, $\\pi^*\\omega$ ex
tends to a holomorphic $2$-form on $Y$. When this extension is actually no
n-degenerate (a de facto symplectic form) on $Y$\, we call $\\pi$ a symple
ctic (or crepant) resolution.\n\nLet $G$ be a complex reductive group and
$A$ an abelian variety of dimension $d$. The aim of this talk is to show t
hat all moduli spaces of $G$-Higgs bundles over $A$ are symplectic varieti
es\, and that\, for $G=\\mathrm{GL}(n\,\\mathbb C)$\, the canonical Hilber
t-Chow morphism is a symplectic resolution if and only if $d=1$.\n\nMoreov
er\, using a little representation theory\, we can obtain explicit express
ions for the Poincaré polynomials of all Hilbert-Chow resolutions (either
$d=1$\, all $n$\; or $n=1\,2\,3$ and all $d$). This is joint work with I.
Biswas and A. Nozad.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/128/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eleonora Di Nezza (Sorbonne Université (IMJ-PRG) and École Norma
le Supérieure de Paris (DMA))
DTSTART:20231031T160000Z
DTEND:20231031T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/129
DESCRIPTION:Title: Singular Kähler-Einstein metrics\nby Eleonora Di Nezza (Sorbo
nne Université (IMJ-PRG) and École Normale Supérieure de Paris (DMA)) a
s part of Geometria em Lisboa (IST)\n\n\nAbstract\nStudying metrics with s
pecial curvature properties on compact Kähler manifolds is a fundamental
problem in Kähler geometry.\nIn this talk\, I will focus on the existence
and uniqueness of singular Kähler-Einstein metrics whose singular behavi
or is prescribed.\nThese results are based on a series of joint works with
T. Darvas and C. Lu.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/129/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cinzia Casagrande (Università di Torino)
DTSTART:20231107T160000Z
DTEND:20231107T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/130
DESCRIPTION:Title: Fano $4$-folds with large Picard number are products of surfaces\nby Cinzia Casagrande (Università di Torino) as part of Geometria em L
isboa (IST)\n\n\nAbstract\nLet $X$ be a smooth\, complex Fano $4$-fold\, a
nd $\\rho(X)$ its Picard number. We will discuss the following theorem: if
$\\rho(X)>12$\, then $X$ is a product of del Pezzo surfaces. This implies
\, in particular\, that the maximal Picard number of a Fano $4$-fold is $1
8$. After an introduction and a discussion of examples\, we explain some o
f the ideas and techniques involved in the proof.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/130/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Benoit Charbonneau (University of Waterloo)
DTSTART:20231107T143000Z
DTEND:20231107T153000Z
DTSTAMP:20260404T094148Z
UID:Geolis/131
DESCRIPTION:Title: Symmetric instantons\nby Benoit Charbonneau (University of Wat
erloo) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nWith Spencer Wh
itehead\, we developed a systematic framework to study instantons on $\\ma
thbb R^4$ that are invariant under groups of isometries. In this presentat
ion\, I will describe this framework and some results obtained using it.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/131/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maarten Mol (Max Planck Institute for Mathematics)
DTSTART:20231121T160000Z
DTEND:20231121T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/132
DESCRIPTION:Title: Kähler manifolds with a high degree of torus bundle symmetry\
nby Maarten Mol (Max Planck Institute for Mathematics) as part of Geometri
a em Lisboa (IST)\n\n\nAbstract\nIn this talk I will discuss a natural gen
eralization of symplectic toric manifolds\, for which the symmetry is give
n by a (symplectic) torus bundle\, rather than a torus. The aim will be to
explain how the Abreu-Guillemin theory of toric Kähler metrics extends t
o this setting. This is based on an ongoing project with Miguel Abreu and
Rui Loja Fernandes.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/132/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sheila Sandon (IRMA-Strasbourg)
DTSTART:20240227T160000Z
DTEND:20240227T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/133
DESCRIPTION:Title: Contact non-squeezing at large scale via generating functions\
nby Sheila Sandon (IRMA-Strasbourg) as part of Geometria em Lisboa (IST)\n
\n\nAbstract\nThe symplectic non-squeezing theorem\, discovered by Gromov
in 1985\, has been the first result showing a fundamental difference betwe
en symplectic transformations and volume preserving ones. A similar but mo
re subtle phenomenon in contact topology was found by Eliashberg\, Kim and
Polterovich in 2006\, and refined by Fraser in 2016 and Chiu in 2017: in
this case\nnon-squeezing depends on the size of the domains\, and only app
ears above a certain quantum scale.\n\nIn my talk I will outline the geome
tric ideas behind a proof of this general contact non-squeezing theorem th
at uses generating functions\, a classical method based on finite dimensio
nal Morse theory. This is a joint work with Maia Fraser and Bingyu Zhang.\
n
LOCATION:https://stable.researchseminars.org/talk/Geolis/133/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Naichung Conan Leung (The Chinese University of Hong Kong)
DTSTART:20240321T160000Z
DTEND:20240321T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/134
DESCRIPTION:Title: Quantization of Kähler manifolds\nby Naichung Conan Leung (Th
e Chinese University of Hong Kong) as part of Geometria em Lisboa (IST)\n\
n\nAbstract\nI will explain recent work on relationships among geometric q
uantization\, deformation quantization\, Berezin-Toeplitz quantization and
brane quantization.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/134/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Levi Lima (Universidade Federal do Ceará)
DTSTART:20240206T160000Z
DTEND:20240206T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/135
DESCRIPTION:Title: Rigidity of non-compact static domains in hyperbolic space via pos
itive mass theorems\nby Levi Lima (Universidade Federal do Ceará) as
part of Geometria em Lisboa (IST)\n\n\nAbstract\nWe introduce a notion of
staticity for non-compact spaces which encompasses several known examples
including any domain in hyperbolic space whose boundary is a non-compact t
otally umbilical hypersurface. For a (time-symmetric) initial data set mod
eled at infinity on any of these latter examples\, we formulate and prove
a positive mass theorem in the spin category under natural dominant energy
conditions (both on the interior and along the boundary) whose rigidity s
tatement in particular retrieves a recent result by Souam to the effect th
at no such umbilical hypersurface admits a compactly supported deformation
keeping the original lower bound for the mean curvature. A key ingredient
in our approach is the consideration of a new boundary condition on spino
rs which somehow interpolates between chirality and MIT bag boundary condi
tions. Joint work with S. Almaraz (arXiv:2206.09768\, to appear in ASNS Pi
sa).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/135/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Filip Živanović (Simons Center for Geometry and Physics at Stony
Brook)
DTSTART:20231212T160000Z
DTEND:20231212T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/136
DESCRIPTION:Title: Filtrations on cohomology from Floer theory of contracting $\\math
bb C^*$-actions\nby Filip Živanović (Simons Center for Geometry and
Physics at Stony Brook) as part of Geometria em Lisboa (IST)\n\n\nAbstract
\nWe study open symplectic manifolds with pseudoholomorphic $\\mathbb C^*$
-actions whose $S^1$-part is Hamiltonian\, and construct their associated
symplectic cohomology. From this construction\, we obtain a filtration on
quantum/ordinary cohomology that depends on the choice of the $\\mathbb C^
*$-action. One should think about this filtration as a Floer-theoretic ana
logue of the Atiyah-Bott filtration. We construct filtration functional on
the Floer chain complex\, allowing us to compute the aforementioned filtr
ation via Morse-Bott spectral sequence that converges to symplectic cohomo
logy\, which is readily computable in examples. We compare our filtration
with known ones from algebraic geometry/representation theory literature.
Time-allowing\, I may present the $S^1$-equivariant picture as well. This
is joint work with Alexander Ritter.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/136/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Liat Kessler (University of Haifa)
DTSTART:20240116T160000Z
DTEND:20240116T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/137
DESCRIPTION:Title: Extending cyclic actions to circle actions\nby Liat Kessler (U
niversity of Haifa) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nIt
is natural to ask whether an action of a finite cyclic group extends to a
circle action. Here\, the action is on a symplectic manifold of dimension
four. Admitting a circle action implies that a simply connected closed sy
mplectic four-manifold is either the projective plane or obtained from an
$S^2$ bundle over $S^2$ by k blowups. I will show that for k small enough\
, any cyclic action that is trivial on homology extends to a circle action
\, and present a case in which the action does not extend. I will also dis
cuss how we approach this question for a general k. The proofs combine hol
omorphic and combinatorial methods. The talk is based on a joint work with
River Chiang.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/137/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jason Lotay (University of Oxford)
DTSTART:20240109T160000Z
DTEND:20240109T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/138
DESCRIPTION:Title: Translators in Lagrangian mean curvature flow\nby Jason Lotay
(University of Oxford) as part of Geometria em Lisboa (IST)\n\n\nAbstract\
nLagrangian mean curvature flow is potentially a powerful tool in solving
problems in symplectic topology. One of the key challenges is the understa
nding of formation of singularities\, which is conjectured to have links t
o J-holomorphic curves\, stability conditions and the Fukaya category. Unl
ike the usual mean curvature flow for hypersurfaces\, here one is expected
to have to tackle singularities modelled on translating solutions to the
flow. I will describe joint work with Felix Schulze and Gabor Szekelyhidi
which allows one to recognize a singularity model in Lagrangian mean curva
ture flow as a translator - this is the first such result in any form of m
ean curvature flow beyond curves.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/138/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rémi Leclercq (Université Paris-Saclay)
DTSTART:20231219T160000Z
DTEND:20231219T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/139
DESCRIPTION:Title: Essential loops of Hamiltonian homeomorphisms\nby Rémi Lecler
cq (Université Paris-Saclay) as part of Geometria em Lisboa (IST)\n\n\nAb
stract\nIn 1987\, Gromov and Eliashberg showed that if a sequence of diffe
omorphisms preserving a symplectic form C⁰ converges to a diffeomorphism
\, the limit also preserves the symplectic form -- even though this is a C
¹ condition. This result gave rise to the notion of symplectic homeomorph
isms\, i.e. elements of the C⁰-closure of the group of symplectomorphism
s in that of homeomorphisms\, and started the study of "continuous symplec
tic geometry".\n\nIn this talk\, I will present recent progress in underst
anding the fundamental group of the C⁰-closure of the group of Hamiltoni
an diffeomorphisms in that of homeomorphisms. More precisely\, I will expl
ain a sufficient condition which ensures that certain essential loops of H
amiltonian diffeomorphisms remain essential when seen as "Hamiltonian home
omorphisms". I will illustrate this method (and its limits) on toric manif
olds\, namely complex projective spaces\, rational products of 2-spheres\,
and rational 1-point blow-ups of CP².\n\nOur condition is based on (expl
icit) computation of the spectral norm of loops of Hamiltonian diffeomorph
isms which is of independent interest. For example\, in the case of 1-poin
t blow-ups of CP²\, I will show that the spectral norm exhibits a surpris
ing behavior which heavily depends on the choice of the symplectic form. T
his is joint work with Vincent Humilière and Alexandre Jannaud.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/139/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yang Li (Massachusetts Institute of Technology)
DTSTART:20240123T160000Z
DTEND:20240123T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/140
DESCRIPTION:Title: On the Thomas-Yau conjecture\nby Yang Li (Massachusetts Instit
ute of Technology) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nThe
Thomas-Yau conjecture is an open-ended program to relate special Lagrangi
ans to stability conditions in Floer theory\, but the precise notion of st
ability is subject to many interpretations. I will focus on the exact case
(Stein Calabi-Yau manifolds)\, and deal only with almost calibrated Lagra
ngians. I will attempt a formulation of Thomas-Yau semistability condition
(meant to be less ambitious than Joyce’s program)\, and focus primarily
on the symplectic aspects\, and the technique of integration over the mod
uli space of holomorphic discs.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/140/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rita Pardini (Universita' di Pisa)
DTSTART:20240220T160000Z
DTEND:20240220T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/141
DESCRIPTION:Title: Exploring the boundary of the moduli space of stable surfaces: som
e explicit examples\nby Rita Pardini (Universita' di Pisa) as part of
Geometria em Lisboa (IST)\n\n\nAbstract\nI will briefly recall the notion
of stable surfaces and of the corresponding moduli space. Then I will outl
ine a partial description of the boundary points in the case of surfaces w
ith $K^2=1$\, $p_g=2$ (joint work with Stephen Coughlan\, Marco Franciosi\
, Julie Rana and Soenke Rollenske\, in various combinations) and\, time pe
rmitting\, in the case of Campedelli and Burniat surfaces (joint work with
Valery Alexeev).\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/141/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shira Tanny (Institute for Advanced Study\, Princeton)
DTSTART:20240305T160000Z
DTEND:20240305T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/142
DESCRIPTION:Title: From Gromov-Witten invariants to dynamics\nby Shira Tanny (Ins
titute for Advanced Study\, Princeton) as part of Geometria em Lisboa (IST
)\n\n\nAbstract\nGiven a flow on a manifold\, how to perturb it in order t
o create a periodic orbit passing through a given region? This question wa
s originally asked by Poincaré and was initially studied in the 60s. Howe
ver\, various facets of it remain largely open. Recently\, several advance
s were made in the context of Hamiltonian and contact flows. I will discus
s a connection between this problem and Gromov-Witten invariants\, which a
re ``counts" of holomorphic curves. This is based on a joint work with Jul
ian Chaidez.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/142/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giordano Cotti (Grupo de Física Matemática\, Universidade de Lis
boa)
DTSTART:20240130T160000Z
DTEND:20240130T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/143
DESCRIPTION:Title: Gromov-Witten theory\, quantum differential equations\, and derive
d categories\nby Giordano Cotti (Grupo de Física Matemática\, Univer
sidade de Lisboa) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nEnum
erative geometry sinks its roots many centuries back in time. In the last
decades\, ideas coming from physics brought innovation to this research ar
ea\, with both new techniques and the emergence of new rich geometrical st
ructures. As an example\, Gromov--Witten theory\, focusing on symplectic i
nvariants defined as counting numbers of curves on a target space\, led to
the notion of quantum cohomology and quantum differential equations (qDEs
).\n\nThe qDEs define a class of ordinary differential equations in the co
mplex domain\, whose study represents a challenging active area in both co
ntemporary geometry and mathematical physics. The qDEs define rich invaria
nts attached to smooth projective varieties. These equations\, indeed\, en
capsulate information not only about the enumerative geometry of varieties
but even (conjecturally) of their topology and complex geometry. The way
to disclose such a huge amount of data is through the study of the asympto
tics and monodromy of their solutions. This talk will be a gentle introduc
tion to the study of qDE's\, their relationship with derived categories of
coherent sheaves (in both non-equivariant and equivariant settings)\, and
a theory of integral representations for its solutions. Overall\, the tal
k will be a survey of the results of the speaker in this research area.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/143/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Frol Zapolsky (University of Haifa & MISANU)
DTSTART:20240227T143000Z
DTEND:20240227T153000Z
DTSTAMP:20260404T094148Z
UID:Geolis/144
DESCRIPTION:Title: Big fiber theorems and symplectic rigidity\nby Frol Zapolsky (
University of Haifa & MISANU) as part of Geometria em Lisboa (IST)\n\n\nAb
stract\nIn many areas of mathematics there are theorems of the following k
ind: Any map in a suitable class has a big fiber. The classes of maps and
the notions of size vary from field to field. In my talk I'll present seve
ral examples of this phenomenon. I'll show how Gromov's notion of ideal va
lued-measures derived from cohomology can be used to prove some of them. I
'll also introduce objects which are a suitable generalization of ideal-va
lued measures in the context of symplectic geometry\, called ideal-valued
quasi-measures\, indicate how they can be constructed using relative sympl
ectic cohomology\, a tool recently introduced by U. Varolgunes\, and demon
strate how they can be used to obtain new symplectic rigidity results. Bas
ed on joint work with A. Dickstein\, Y. Ganor\, and L. Polterovich.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/144/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cristiano Spotti (Aarhus University)
DTSTART:20240312T160000Z
DTEND:20240312T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/145
DESCRIPTION:Title: Algebro geometric aspects of bubbling of Kähler-Einstein metrics<
/a>\nby Cristiano Spotti (Aarhus University) as part of Geometria em Lisbo
a (IST)\n\n\nAbstract\nGiven a degenerating family of Kähler-Einstein met
rics it is natural to study from a differential geometric perspective the
collection of all metric limits at all possible scales\, a typical example
being the emergence of Kronheimer’s ALE spaces near the formation of or
bifold singularities for Einstein 4-manifolds. In this talk\, I will descr
ibe\, focusing on the discussion of some concrete and elementary examples\
, how it should be possible to use algebro geometric tools to investigate
such problem for algebraic families\, leading in the non-collapsing case t
o an inductive argument identifying the so-called metric bubble tree at a
singularity (made of a collection of asymptotically conical Calabi-Yau var
ieties) with a subset of the non-Archimedean Berkovich analytification of
the family. Based on joint work with M. de Borbon.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/145/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joé Brendel (Université de Neuchâtel)
DTSTART:20240402T150000Z
DTEND:20240402T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/146
DESCRIPTION:Title: Local constructions of exotic Lagrangian tori\nby Joé Brendel
(Université de Neuchâtel) as part of Geometria em Lisboa (IST)\n\n\nAbs
tract\nCertain simple symplectic manifolds (symplectic vector space\, Miln
or fibres of certain complex surface singularities\,...) contain sets of s
ymplectically distinct Lagrangian tori which have the following remarkable
property: they remain symplectically distinct under embeddings into any r
easonable (i.e. geometrically bounded) symplectic manifold. This leads to
a vast extension of the class of spaces in which the existence of exotic t
ori is known\, especially in dimensions six and above. In this talk we mai
nly focus on recent joint work with Johannes Hauber and Joel Schmitz which
treats the more intricate case of dimension four.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/146/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Diogo Oliveira e Silva (Instituto Superior Técnico)
DTSTART:20240716T150000Z
DTEND:20240716T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/147
DESCRIPTION:Title: Sharp extension inequalities on finite fields\nby Diogo Olivei
ra e Silva (Instituto Superior Técnico) as part of Geometria em Lisboa (I
ST)\n\n\nAbstract\nSharp restriction theory and the finite field extension
problem have both received much attention in the last two decades\, but s
o far they have not intersected. In this talk\, we discuss our first resul
ts on sharp restriction theory on finite fields. Even though our methods f
or dealing with paraboloids and cones borrow some inspiration from their e
uclidean counterparts\, new phenomena arise which are related to the under
lying arithmetic and discrete structures. The talk is based on recent join
t work with Cristian González-Riquelme.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/147/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kiumars Kaveh (University of Pittsburgh)
DTSTART:20240618T150000Z
DTEND:20240618T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/148
DESCRIPTION:Title: A spherical logarithm map\nby Kiumars Kaveh (University of Pit
tsburgh) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nThe logarithm
map from complex algebraic torus to the Euclidean space\, sends an n-tupl
e of nonzero complex numbers to the logarithms of their absolute values. T
he image of a subvariety in the torus under the logarithm map is called "
amoeba" and it contains geometric information about the variety. In this t
alk we explore the extension of the notion of logarithm map and amoeba to
the non-commutative setting\, that is for a spherical homogeneous space G/
H where G is a connected complex reductive algebraic group. This is relate
d to Victor Batyrev's question of describing K-orbits in G/H.\nThe talk is
based on a join work with Victor Batyrev\, Megumi Harada and Johannes Hof
scheier.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/148/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leander Stecker (Instituto Superior Técnico)
DTSTART:20240430T150000Z
DTEND:20240430T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/149
DESCRIPTION:Title: Canonical Submersions and 3-$(\\alpha\, \\delta)$-Sasaki geometry
*\nby Leander Stecker (Instituto Superior Técnico) as part of Geometr
ia em Lisboa (IST)\n\n\nAbstract\nWe introduce the classical results of de
Rham and Berger on the holonomy of a Riemannian manifold. We compare thes
e to the situation of parallel skew-torsion\, where we obtain Riemannian s
ubmersions from reducible holonomy. If time permits I will give an introdu
ction to 3-$(\\alpha\, \\delta)$-Sasaki manifolds and their submersion ont
o quaternionic Kähler manifolds.\n*if time permits\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/149/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Robalo (Institut de Mathematiques de Jussieu-Paris Rive Gauc
he)
DTSTART:20240507T150000Z
DTEND:20240507T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/150
DESCRIPTION:Title: Gluing Invariants of Donaldson-Thomas Type\nby Marco Robalo (I
nstitut de Mathematiques de Jussieu-Paris Rive Gauche) as part of Geometri
a em Lisboa (IST)\n\n\nAbstract\nIn this talk I will explain a general mec
hanism\, based on derived symplectic geometry\, to glue the local invarian
ts of singularities that appear naturally in Donaldson-Thomas theory. Our
mechanism recovers the categorified vanishing cycles sheaves constructed b
y Brav-Bussi-Dupont-Joyce\, and provides a new more evolved gluing of Orlo
v’s categories of matrix factorisations\, answering a conjecture of Kont
sevich-Soibelman and Y.Toda. This is a joint work with B. Hennion (Orsay)
and J. Holstein (Hamburg). The talk will be accessible to a general audien
ce.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/150/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alex Waldron (University of Wisconsin -Madison)
DTSTART:20240702T150000Z
DTEND:20240702T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/151
DESCRIPTION:Title: Łojasiewicz inequalities for maps of the 2-sphere\nby Alex Wa
ldron (University of Wisconsin -Madison) as part of Geometria em Lisboa (I
ST)\n\n\nAbstract\nInfinite-time convergence of geometric flows\, as even
for finite-dimensional gradient flows\, is a notoriously subtle problem. T
he best (or only) bet is to get a ``Łojasiewicz(-Simon) inequality'' stat
ing that a power of the gradient dominates the distance to the critical en
ergy value. I'll introduce a Łojasiewicz inequality between the tension f
ield and Dirichlet energy of a map from the 2-sphere to itself\, removing
the technical restrictions from an estimate of Topping (Annals '04). The i
nequality guarantees convergence of weak solutions of harmonic map flow fr
om $S^2$ to $S^2$ assuming that the body map is nonconstant.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/151/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pazit Haim-Kislev (Tel-Aviv University)
DTSTART:20240528T150000Z
DTEND:20240528T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/152
DESCRIPTION:Title: On the existence of symplectic barriers\nby Pazit Haim-Kislev
(Tel-Aviv University) as part of Geometria em Lisboa (IST)\n\n\nAbstract\n
Lagrangian submanifold rigidity has been a fundamental topic in symplectic
topology\, contributing to key theories like the Arnold-Givental conjectu
re and Lagrangian Floer theory. These theories often show that intersectio
ns between Lagrangian submanifolds are unavoidable via symplectic maps\, e
xemplified by Biran's concept of Lagrangian Barriers (2001).\nConversely\,
submanifolds not containing Lagrangian submanifolds usually exhibit flexi
bility\, and can often be symplectically displaced. In this joint work wit
h Richard Hind and Yaron Ostrover\, we introduce what appears to be the fi
rst illustration of Symplectic Barriers\, demonstrating necessary intersec
tions of symplectic embeddings with symplectic (non-Lagrangian) submanifol
ds. The key point is that Lagrangian submanifolds are not the sole barrier
s\, and there exist situations where a symplectic submanifold is not flexi
ble. \nIn our work\, we also answer a question by Sackel–Song–Varolgu
nes–Zhu and calculate the optimal symplectic ball embedding in the ball
after removing a codimension 2 hyperplane with a prescribed Kähler angle.
\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/152/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alejandro Cabrera (Universidade Federal do Rio de Janeiro)
DTSTART:20240625T150000Z
DTEND:20240625T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/153
DESCRIPTION:Title: About an instanton-type PDE for Poisson geometry\nby Alejandro
Cabrera (Universidade Federal do Rio de Janeiro) as part of Geometria em
Lisboa (IST)\n\n\nAbstract\nIn this talk\, I will present an instanton-typ
e PDE associated with a Poisson manifold M. After reviewing its role in an
underlying field theory\, we present the main theorem showing existence a
nd classification of its solutions. Finally\, we discuss its geometric sig
nificance leading to a generating function for a symplectic groupoid\, Lie
-theoretic\, integration of M.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/153/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mingyang Li (University of Berkeley)
DTSTART:20240521T150000Z
DTEND:20240521T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/154
DESCRIPTION:Title: Classification results for Hermitian non-Kähler gravitational ins
tantons\nby Mingyang Li (University of Berkeley) as part of Geometria
em Lisboa (IST)\n\n\nAbstract\nWe will discuss some classification results
for Hermitian non-Kähler gravitational instantons. There are three main
results: (1) Non-existence of certain Hermitian non-Kähler ALE gravitatio
nal instantons. (2) Complete classification for Hermitian non-Kähler ALF/
AF gravitational instantons. (3) Non-existence of Hermitian non-Kähler gr
avitational instantons under suitable curvature decay condition\, when the
re is more collapsing at infinity (ALG\, ALH\, etc.). These are achieved b
y a thorough analysis of the collapsing geometry at infinity and compactif
ications.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/154/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dan Wang (CAMGSD\, Instituto Superior Técnico)
DTSTART:20241119T160000Z
DTEND:20241119T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/155
DESCRIPTION:Title: Dependence of quantum spaces on different polarizations on toric v
arieties\nby Dan Wang (CAMGSD\, Instituto Superior Técnico) as part o
f Geometria em Lisboa (IST)\n\n\nAbstract\nA crucial problem in geometric
quantization is to understand the relationship among quantum spaces associ
ated to different polarizations. Two types of polarizations on toric varie
ties\, Kähler and real\, have been studied extensively. This talk will fo
cus on the quantum spaces associated with mixed polarizations and explore
their relationships with those associated with Kähler polarizations on to
ric varieties.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/155/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Miguel Moreira (MIT)
DTSTART:20250107T160000Z
DTEND:20250107T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/156
DESCRIPTION:Title: Intersection theory on moduli spaces of parabolic bundles\nby
Miguel Moreira (MIT) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nT
he geometry\, topology and intersection theory of moduli spaces of stable
vector bundles on curves have been topics of interest for more than 50 yea
rs. In the 90s\, Jeffrey and Kirwan managed to prove a formula proposed by
Witten for the intersection numbers of tautological classes on such modul
i spaces. In this talk\, I will explain a different way to calculate those
numbers and\, more generally\, intersection numbers on moduli of paraboli
c bundles. Enriching the problem with a parabolic structure gives access t
o powerful tools\, such as wall-crossing\, Hecke transforms and Weyl symme
try. If time allows\, I will explain how this approach gives a new proof o
f (a generalization to the parabolic setting of) a vanishing result conjec
tured by Newstead and proven by Earl and Kirwan.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/156/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dario Di Pinto (CMUC\, University of Lisbon)
DTSTART:20241001T150000Z
DTEND:20241001T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/157
DESCRIPTION:Title: Geometry and topology of anti-quasi-Sasakian manifolds\nby Dar
io Di Pinto (CMUC\, University of Lisbon) as part of Geometria em Lisboa (
IST)\n\n\nAbstract\nIn the present talk I will introduce a new class of al
most contact metric manifolds\, called anti-quasi-Sasakian (aqS for short)
. They are non-normal almost contact metric manifolds $(M\,\\varphi\,\\xi\
,\\eta\,g)$\, locally fibering along the 1-dimensional foliation generated
by $\\xi$ onto Kähler manifolds endowed with a closed 2-form of type (2\
,0). Various examples of anti-quasi-Sasakian manifolds will be provided\,
including compact nilmanifolds\, $\\mathbb{S}^1$-bundles and manifolds adm
itting a $Sp(n)\\times \\{1\\}$-reduction of the structural group of the f
rame bundle. Then\, I will discuss some geometric obstructions to the exis
tence of aqS structures\, mainly related to curvature and topological prop
erties. In particular\, I will focus on compact manifolds endowed with aqS
structures of maximal rank\, showing that they cannot be homogeneous and
they must satisfy some restrictions on the Betti numbers.\n\nThis is based
on joint works with Giulia Dileo (Bari) and Ivan Yudin (Coimbra).\n\nRefe
rences\n\n1. D. Di Pinto\, On anti-quasi-Sasakian manifolds of maximal ran
k J. Geom. Phys. 200 (2024)\, Paper no. 105174\, 10 pp.\n\n2. D. Di Pinto\
, G. Dileo\, Anti-quasi-Sasakian manifolds\, Ann. Global Anal. Geom. 64 (1
)\, Article no. 5 (2023)\, 35 pp.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/157/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Francisco Nascimento (Instituto Superior Técnico\, Universidade d
e Lisboa)
DTSTART:20241203T160000Z
DTEND:20241203T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/158
DESCRIPTION:Title: Kinematic formulas in convex geometry\nby Francisco Nascimento
(Instituto Superior Técnico\, Universidade de Lisboa) as part of Geometr
ia em Lisboa (IST)\n\n\nAbstract\nWe present a systematic study of kinemat
ic formulas in convex geometry. We first give a classical presentation of
kinematic formulas for integration with respect to the rotation group $SO(
n)$\, where Steiner's Formula\, the intrinsic volumes and Hadwiger's Chara
cterization Theorem play a crucial role. Then we will show a new extension
to integration along the general linear group $GL(n)$. Using the bijectio
n of matrix polar decomposition and a Gaussian measure to integrate along
positive definite matrices\, a new formula is obtained\, for which the cla
ssical $SO(n)$ formula is a particular case. We also reference the unitary
group $U(n)$ case and its corresponding extension to the symplectic group
$Sp(2n\,\\mathbb{R})$.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/158/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Saman Habibi Esfahani (Duke University)
DTSTART:20241105T160000Z
DTEND:20241105T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/159
DESCRIPTION:Title: On the Donaldson-Scaduto conjecture\nby Saman Habibi Esfahani
(Duke University) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nThis
talk is based on a joint work with Yang Li. Motivated by collapsing Calab
i-Yau 3-folds and G2-manifolds with Lefschetz K3 fibrations in the adiabat
ic setting\, Donaldson and Scaduto conjectured the existence of a special
Lagrangian pair-of-pants in the Calabi-Yau 3-fold $X \\times \\mathbb R^2$
\, where $X$ is either a hyperkähler K3 surface (global version) or an A2
-type ALE hyperkähler 4-manifold (local version). After a brief introduct
ion to the subject\, we discuss the significance of this conjecture in the
study of Calabi-Yau 3-folds and G2-manifolds\, and then prove the local v
ersion of the conjecture\, which in turn implies the global version for an
open subset of the moduli of K3 surfaces.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/159/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yu-Shen Lin (Boston University)
DTSTART:20241112T160000Z
DTEND:20241112T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/160
DESCRIPTION:Title: Special Lagrangians in Calabi-Yau $3$-folds with a K3-fibration\nby Yu-Shen Lin (Boston University) as part of Geometria em Lisboa (IST)
\n\n\nAbstract\nSpecial Lagrangians form an important class of minimal sub
manifolds in Calabi-Yau manifolds. In this talk\, we will consider the Cal
abi-Yau $3$-folds with a K3-fibration and the size of the K3-fibres are sm
all. Motivated by tropical geometry\, Donaldson-Scaduto conjectured that s
pecial Lagrangian collapse to ``gradient cycles" when the K3-fibres collap
se. This phenomenon is similar to holomorphic curves in Calabi-Yau manifol
ds with collapsing special Lagrangian fibrations converging to tropical cu
rves. Similar to the realization problem in tropical geometry\, one might
expect to reconstruct special Lagrangians from gradient cycles. In this ta
lk\, I will report the first theorem of this kind based on a joint work wi
th Shih-Kai Chiu.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/160/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Naichung Conan Leung (The Chinese University of Hong Kong)
DTSTART:20241217T160000Z
DTEND:20241217T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/161
DESCRIPTION:Title: 3d mirror symmetry is mirror symmetry\nby Naichung Conan Leung
(The Chinese University of Hong Kong) as part of Geometria em Lisboa (IST
)\n\n\nAbstract\n3d mirror symmetry is a mysterious duality for certian pa
irs of hyperkähler manifolds\, or more generally complex symplectic manif
olds/stacks. In this talk\, we will describe its relationships with 2d mir
ror symmetry. This could be regarded as a 3d analog of the paper "Mirror S
ymmetry is T-Duality" by Strominger\, Yau and Zaslow which described 2d mi
rror symmetry via 1d dualities.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/161/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Samuel Muñoz-Echániz (University of Cambridge)
DTSTART:20250114T160000Z
DTEND:20250114T170000Z
DTSTAMP:20260404T094148Z
UID:Geolis/162
DESCRIPTION:Title: Mapping class groups of h-cobordant manifolds\nby Samuel Muño
z-Echániz (University of Cambridge) as part of Geometria em Lisboa (IST)\
n\n\nAbstract\nA cobordism W between compact manifolds M and M’ is an h-
cobordism if the inclusions of M and M’ into W are both homotopy equival
ences. These sort of cobordisms play an important role in the classificati
on of high-dimensional manifolds\, as h-cobordant manifolds are often diff
eomorphic.\n\nWith this in mind\, given two h-cobordant manifolds M and M'
\, how different can their diffeomorphism groups Diff(M) and Diff(M') be?
The homotopy groups of these two spaces are the same “up to extensions
” in a range of strictly positive degrees. Contrasting this\, I will pre
sent examples of h-cobordant manifolds in high-dimensions with different m
apping class groups. In doing so\, I will review the classical theory of h
-cobordisms and introduce several moduli spaces of manifolds that shed lig
ht on this question.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/162/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nick Sheridan (University of Edinburgh)
DTSTART:20250311T150000Z
DTEND:20250311T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/163
DESCRIPTION:Title: Quantum cohomology as a deformation of symplectic cohomology\n
by Nick Sheridan (University of Edinburgh) as part of Geometria em Lisboa
(IST)\n\n\nAbstract\nWhen M is a Fano variety and D is an anticanonical di
visor in M\, mirror symmetry suggests that the quantum cohomology of M sho
uld be a deformation of the symplectic cohomology of M \\ D. We prove that
this holds under even weaker hypotheses on D (although not in general)\,
and explain the consequences for mirror symmetry. We also explain how our
methods give rise to interesting symplectic rigidity results for subsets o
f M. Along the way we hope to give a brief introduction to Varolgunes' `re
lative symplectic cohomology'\, which is the key technical tool used to pr
ove our symplectic rigidity results\, but which is of far broader signific
ance in symplectic topology and mirror symmetry as it makes the computatio
n of quantum cohomology `local'. This is joint work with Strom Borman\, Mo
hamed El Alami\, and Umut Varolgunes.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/163/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ana Rita Pires (University of Edinburgh)
DTSTART:20250218T150000Z
DTEND:20250218T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/164
DESCRIPTION:Title: Infinite staircases in ball packing problems\nby Ana Rita Pire
s (University of Edinburgh) as part of Geometria em Lisboa (IST)\n\n\nAbst
ract\nThe symplectic version of the problem of packing K balls into a ball
in the densest way possible (in 4 dimensions) can be extended to that of
symplectically embedding an ellipsoid into a ball as small as possible. A
classic result due to McDuff and Schlenk asserts that the function that en
codes this problem has a remarkable structure: its graph has infinitely ma
ny corners\, determined by Fibonacci numbers\, that fit together to form a
n infinite staircase.\n\nThis ellipsoid embedding function can be equally
defined for other targets\, and this talk will be about other targets for
which the function has and does not have an infinite staircase. Firstly we
will see how in the case when these targets have lattice moment polygons\
, the targets with infinite staircases seem to be exactly those whose poly
gon is reflexive (i.e.\, has one interior lattice point). Secondly\, we wi
ll look at the family of one-point blowups of CP^2\, where the answer invo
lves self-similar behaviour akin to the Cantor set.\n\nThis talk is based
on various projects\, joint with Dan Cristofaro-Gardiner\, Tara Holm\, Ale
ssia Mandini\, Maria Bertozzi\, Tara Holm\, Emily Maw\, Dusa McDuff\, Grac
e Mwakyoma\, Morgan Weiler\, and Nicki Magill.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/164/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gonçalo Oliveira (Instituto Superior Técnico - University of Lis
bon)
DTSTART:20250225T150000Z
DTEND:20250225T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/165
DESCRIPTION:Title: Special Lagrangians and mean curvature flow on Gibbons-Hawking man
ifolds\nby Gonçalo Oliveira (Instituto Superior Técnico - University
of Lisbon) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nMirror sym
metry is a somewhat mysterious phenomenon that relates the geometry of two
distinct Calabi-Yau manifolds. In the realm of trying to understand this
relationship several conjectures on the existence of so-called special Lag
rangian submanifolds appeared. In this talk\, I will report on joint work
with Jason Lotay on which we prove versions of the Thomas and Thomas-Yau c
onjectures regarding the existence of these special Lagrangian submanifold
s and the role of Lagrangian mean curvature flow as a way to find them. I
will also report on some more recent work towards proving more recent conj
ectures due to Joyce.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/165/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ana Cannas (ETH Zurich)
DTSTART:20250506T140000Z
DTEND:20250506T150000Z
DTSTAMP:20260404T094148Z
UID:Geolis/166
DESCRIPTION:Title: Real Toric Lagrangians\nby Ana Cannas (ETH Zurich) as part of
Geometria em Lisboa (IST)\n\n\nAbstract\nWe fix an arbitrary symplectic to
ric manifold M. Its real toric lagrangians are the lagrangian submanifolds
of M whose intersection with each torus orbit is clean and an orbit of th
e subgroup of elements that square to the identity of the torus (basically
that subgroup is $\\{ 1 \, -1\\}^n$). In particular\, real toric lagrangi
ans are transverse to the principal torus orbits and retain as much symmet
ry as possible.\n\nThis talk will explain why any two real toric lagrangia
ns in M are related by an equivariant symplectomorphism and\, therefore\,
any real toric lagrangian must be the real locus for a real structure pres
erving the moment map. This is joint work with Yael Karshon.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/166/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leonardo Macarini (IMPA)
DTSTART:20250909T140000Z
DTEND:20250909T150000Z
DTSTAMP:20260404T094148Z
UID:Geolis/167
DESCRIPTION:Title: Existence and localization of closed magnetic geodesics with low e
nergy\nby Leonardo Macarini (IMPA) as part of Geometria em Lisboa (IST
)\n\n\nAbstract\nMagnetic flows are generalizations of geodesic flows that
describe the motion of a charged particle in a magnetic field. While ever
y closed Riemannian manifold admits at least one closed geodesic\, the ana
logous problem for magnetic orbits (also known as magnetic geodesics) is s
ignificantly more challenging and has received considerable attention in r
ecent decades. I will present a result establishing that every low energy
level of any magnetic flow admits at least one contractible closed orbit\,
assuming only that the magnetic strength is not identically zero\, has a
compact strict local maximum K\, and that the cohomology class of the magn
etic field is spherically rational. Moreover\, this magnetic geodesic can
be localized within an arbitrarily small neighborhood of K. This is joint
work with Valerio Assenza and Gabriele Benedetti.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/167/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Martin Pinsonnault (University of Western Ontario in London)
DTSTART:20250605T143000Z
DTEND:20250605T153000Z
DTSTAMP:20260404T094148Z
UID:Geolis/168
DESCRIPTION:Title: Embeddings of more than 8 symplectic balls in $\\mathbb CP^2$\
nby Martin Pinsonnault (University of Western Ontario in London) as part o
f Geometria em Lisboa (IST)\n\n\nAbstract\nWe prove that the space of symp
lectic embeddings of $n\\geq 1$ standard balls\, each of capacity at most
$\\frac{1}{n}$\, into the standard complex projective plane $\\mathbb CP^2
$ is homotopy equivalent to the configuration space of $n$ points in $\\ma
thbb CP^2$. Our techniques also suggest that for every $n \\geq 9$\, there
may exist infinitely many homotopy types of spaces of symplectic ball emb
eddings.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/168/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jarek Kedra (University of Aberdeen)
DTSTART:20250624T140000Z
DTEND:20250624T150000Z
DTSTAMP:20260404T094148Z
UID:Geolis/169
DESCRIPTION:Title: Configuration spaces of symplectic balls\nby Jarek Kedra (Univ
ersity of Aberdeen) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nI
will report on the work in progress with S.Anjos and M.Pinsonnault concern
ing configuration spaces of symplectic balls in the standard complex proje
ctive plane. A few weeks ago Martin showed that when the balls are small t
heir configuration space is homotopy equivalent to the configuration space
of points. I will discuss what is happening if the balls are bigger. I wi
ll also try to put it into a more general context of configuration of rigi
d balls in domains of a Euclidean space.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/169/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Da Rong Cheng (University of Miami)
DTSTART:20250527T140000Z
DTEND:20250527T150000Z
DTSTAMP:20260404T094148Z
UID:Geolis/170
DESCRIPTION:Title: SU(2) Yang-Mills-Higgs functional with self-interaction term on 3-
manifolds\nby Da Rong Cheng (University of Miami) as part of Geometria
em Lisboa (IST)\n\n\nAbstract\nI will talk about recent joint work with D
aniel Fadel (University of São Paulo) and Luiz Lara (Unicamp)\, where we
study the SU(2) Yang-Mills-Higgs functional with positive coupling constan
t on 3-manifolds. Motivated by the work of Alessandro Pigati and Daniel St
ern (2021) on the U(1)-version of the functional\, we also include a scali
ng parameter.\n\nWhen the 3-manifold is closed and the parameter is small
enough\, by adapting to our context the min-max method used by Pigati and
Stern\, we construct non-trivial critical points satisfying energy upper a
nd lower bounds that are natural from the point of view of scaling.\n\nThe
n\, over 3-manifolds with bounded geometry\, we show that\, in the limit a
s the parameter tends to zero\, and under the above-mentioned energy upper
bound\, a sequence of critical points exhibits concentration phenomenon a
t a finite collection of points\, while the remaining energy goes into an
$L^2$ harmonic 1-form. Moreover\, the concentrated energy at each point is
accounted for by finitely many "bubbles"\, that is\, non-trivial critical
points on $R^3$ with the scaling parameter set to 1.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/170/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rui Loja Fernandes (University of Illinois Urbana-Champaign)
DTSTART:20250612T093000Z
DTEND:20250612T103000Z
DTSTAMP:20260404T094148Z
UID:Geolis/171
DESCRIPTION:Title: Extremal Kähler Metrics on Toric Lagrangian Fibrations\nby Ru
i Loja Fernandes (University of Illinois Urbana-Champaign) as part of Geom
etria em Lisboa (IST)\n\n\nAbstract\nA toric Lagrangian fibration is a Lag
rangian fibration whose singular fibers are all of elliptic type. I will b
egin by explaining how such fibrations can be viewed as Hamiltonian spaces
associated with symplectic torus bundles. I will then discuss a generaliz
ation to this class of fibrations of the Abreu–Guillemin–Donaldson the
ory of extremal Kähler metrics on toric symplectic manifolds. Integral af
fine geometry plays a central role in this generalization\, as the Delzant
polytope is replaced by a more general domain contained in an integral af
fine manifold. This talk is based on on-going work with Miguel Abreu and M
aarten Mol.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/171/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alejandro Cabrera (Universidade Federal do Rio de Janeiro)
DTSTART:20250715T140000Z
DTEND:20250715T150000Z
DTSTAMP:20260404T094148Z
UID:Geolis/172
DESCRIPTION:Title: Numerical approximation of Hamiltonian flows on Poisson manifolds
and groupoid multiplication\nby Alejandro Cabrera (Universidade Federa
l do Rio de Janeiro) as part of Geometria em Lisboa (IST)\n\n\nAbstract\nT
he idea is to construct numerical integrator methods for Hamiltonian type
of ODE’s which are defined in an ambient Poisson geometry. The goal is t
o approximate the exact dynamical solutions of this ODE while\, at the sam
e time\, preserve the Poisson structure to a certain controlled degree. Th
is is a non-trivial and long-range generalization of the notion of symplec
tic method in which the Poisson geometry is non-degenerate\, thus\, symple
ctic. We first outline a first approach to such methods which uses the geo
metry of so-called approximate symplectic realizations based on recent joi
nt work with D. Martín de Diego and M. Vaquero. Finally\, we describe a s
econd approach based on theoretical results coming from Lie-theoretic aspe
cts and which use an underlying groupoid multiplication\, based on work in
progress with D. Iglesias and J.C. Marrero.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/172/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marcelo Atallah (University of Sheffield)
DTSTART:20251007T140000Z
DTEND:20251007T150000Z
DTSTAMP:20260404T094148Z
UID:Geolis/173
DESCRIPTION:Title: C⁰-rigidity of the Hamiltonian diffeomorphism group of symplecti
c rational surfaces\nby Marcelo Atallah (University of Sheffield) as p
art of Geometria em Lisboa (IST)\n\n\nAbstract\nA natural question bridgin
g the celebrated Gromov–Eliashberg theorem and the C⁰-flux conjecture
is whether the identity component of the group of symplectic diffeomorphis
ms is C⁰-closed in Symp(M\,ω). Beyond surfaces and the cases in which t
he Torelli subgroup of Symp(M\,ω) coincides with the identity component\,
little is known. In joint work with Cheuk Yu Mak and Wewei Wu\, we show t
hat\, for all but a few positive rational surfaces\, the group of Hamilton
ian diffeomorphisms is the C⁰-connected component of the identity in Sym
p(M\,ω)\, thereby giving a positive answer in this setting. Here\, “pos
itive rational surface” essentially means a k-point blow-up of CP² whos
e symplectic form evaluates positively on the first Chern class.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/173/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marta Batoreo (Universidade Federal do Espírito Santo)
DTSTART:20250923T140000Z
DTEND:20250923T150000Z
DTSTAMP:20260404T094148Z
UID:Geolis/174
DESCRIPTION:Title: On the number of periodic points of symplectomorphisms on surfaces
\nby Marta Batoreo (Universidade Federal do Espírito Santo) as part o
f Geometria em Lisboa (IST)\n\n\nAbstract\nIn this talk I will survey some
results on the existence of periodic points of symplectomorphisms defined
on closed orientable surfaces of positive genus g. Namely\, I will descri
be some symplectic flows on such surfaces possessing finitely many periodi
c points and describe a non-Hamiltonian variant of the Hofer-Zehnder conje
cture for symplectomorphisms defined on surfaces\; this conjecture provide
s a quantitative threshold on the number of fixed points (possibly counted
homologically) which forces the existence of infinitely many periodic poi
nts. This is joint work in progress with Marcelo Atallah and Brayan Ferrei
ra.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/174/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mingyang Li (Simons Center for Geometry and Physics)
DTSTART:20251028T150000Z
DTEND:20251028T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/175
DESCRIPTION:Title: Gravitational instantons and harmonic maps\nby Mingyang Li (Si
mons Center for Geometry and Physics) as part of Geometria em Lisboa (IST)
\n\n\nAbstract\nIt is known from general relativity that axisymmetric stat
ionary black holes can be reduced to axisymmetric harmonic maps into the h
yperbolic plane H^2\, while in the Riemannian setting\, 4d Ricci-flat metr
ics with torus symmetry can also be locally reduced to such harmonic maps
satisfying a tameness condition. We study such harmonic maps. Applications
include a construction of infinitely many new complete\, asymptotically f
lat\, Ricci-flat 4-manifolds with arbitrarily large b_2. Joint work with S
ong Sun.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/175/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joé Brendel (ETH Zurich)
DTSTART:20251118T150000Z
DTEND:20251118T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/176
DESCRIPTION:Title: Knotted bi-disk embeddings\nby Joé Brendel (ETH Zurich) as pa
rt of Geometria em Lisboa (IST)\n\n\nAbstract\nA classical result by McDuf
f shows that the space of symplectic ball embeddings into many simple symp
lectic four-manifolds is connected. In this talk\, on the other hand\, we
show that the space of symplectic bi-disk embeddings often has infinitely
many connected components\, even for simple target spaces like the complex
projective plane\, or the symplectic ball. This extends earlier results b
y Gutt-Usher and Dimitroglou-Rizell. The proof uses almost toric fibration
s and exotic Lagrangian tori. Furthermore\, we will discuss natural quanti
tative questions arising in this context. This talk is based on joint work
in progress with Grigory Mikhalkin and Felix Schlenk.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/176/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tristan Ozuch (Massachusetts Institute of Technology)
DTSTART:20251209T150000Z
DTEND:20251209T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/177
DESCRIPTION:by Tristan Ozuch (Massachusetts Institute of Technology) as pa
rt of Geometria em Lisboa (IST)\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/177/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rui Loja Fernandes (University of Illinois Urbana-Champaign)
DTSTART:20260106T150000Z
DTEND:20260106T160000Z
DTSTAMP:20260404T094148Z
UID:Geolis/178
DESCRIPTION:Title: Resolutions of proper actions and toric manifolds\nby Rui Loja
Fernandes (University of Illinois Urbana-Champaign) as part of Geometria
em Lisboa (IST)\n\n\nAbstract\nI will define a notion of resolution of a p
roper action. Such resolutions always exist but are not canonical. However
\, for so-called polar actions I will describe a canonical construction of
a resolution\, which can be used to show that the leaf space has the stru
cture of an orbifold. I will illustrate this construction with two example
s: (i) the adjoint action\, where it allows one to identify the classical
Weyl group with the orbifold fundamental group\; and (ii) toric manifolds\
, where the resolution can be described in terms of the real part of the t
oric manifold.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/178/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pierre Martinez (Université de Bretagne Occidentale)
DTSTART:20260219T140000Z
DTEND:20260219T150000Z
DTSTAMP:20260404T094148Z
UID:Geolis/179
DESCRIPTION:Title: Bigraded cohomology for real algebraic varieties and its arithmeti
c variant\nby Pierre Martinez (Université de Bretagne Occidentale) as
part of Geometria em Lisboa (IST)\n\n\nAbstract\nI will first introduce t
he bigraded cohomology for real algebraic varieties developed by Johannes
Huisman and Dewi Gleuher. This is a cohomology theory that refines the equ
ivariant cohomology "à la Kahn-Krasnov" of the complex points of a real v
ariety\, the latter often being preferred (by the algebraic geometers) in
the cohomological study of real algebraic varieties. Since the constructio
n of this bigraded cohomology and its associated characteristic classes re
lies on the sheaf exponential morphism\, I will explain how to produce an
arithmetic (or algebraic) variant of these cohomology groups\, whose main
advantage is toeliminate topological or transcendental conditions. I will
conclude by comparing these two versions of bigraded cohomology.\n
LOCATION:https://stable.researchseminars.org/talk/Geolis/179/
END:VEVENT
END:VCALENDAR