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BEGIN:VEVENT
SUMMARY:Henri Guenancia (CNRS - Univ. Toulouse)
DTSTART:20200508T150000Z
DTEND:20200508T163000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/1
DESCRIPTION:Title: Families of singular Kähler-Einstein metrics\nby Henri Guenanci
a (CNRS - Univ. Toulouse) as part of CRM - Séminaire du CIRGET / Géomét
rie et Topologie\n\n\nAbstract\nI will outline the main results and ideas
from a recent joint work with E. Di Nezza and V. Guedj. The general theme
is as follows: let p:X\\to Y be a holomorphic\, proper surjective map from
a complex Kähler space X and assume that the fibers X_y admit some (poss
ibly twisted) singular Kähler-Einstein metric. We show that the potential
s of these metrics admit uniform bounds when y varies in compact subsets.
If time permits\, I will mention a connection with an earlier work (joint
with J. Cao and M. Paun) on the psh variation of the Kähler-Einstein metr
ic on families of manifolds of general type.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ekaterina Amerik (Univ. Paris Sud)
DTSTART:20200515T150000Z
DTEND:20200515T163000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/2
DESCRIPTION:Title: Around the cone conjecture for hyperkähler manifolds\nby Ekater
ina Amerik (Univ. Paris Sud) as part of CRM - Séminaire du CIRGET / Géom
étrie et Topologie\n\n\nAbstract\nThe Morrison-Kawamata cone conjecture s
tates that the automorphism group of a Calabi-Yau manifold acts with finit
ely many orbits on the set of faces of its ample cone. I shall sketch its
proof in the hyperkähler case with some emphasis on a statement on Lie gr
oups behind it. All results\nare joint work with Misha Verbitsky.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Patrick Orson (Boston College)
DTSTART:20200522T150000Z
DTEND:20200522T163000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/3
DESCRIPTION:Title: Topologically embedding spheres in knot traces\nby Patrick Orson
(Boston College) as part of CRM - Séminaire du CIRGET / Géométrie et T
opologie\n\n\nAbstract\nKnot traces are smooth 4-manifolds with boundary\,
that are homotopic to the 2-sphere\, and obtained by attaching a 2-handle
to the 4-ball along a framed knot in the 3-sphere. I will give a complete
characterisation for when the generator of the second homotopy group of a
knot trace can be represented by a locally flat embedded 2-sphere with ab
elian exterior fundamental group. The answer is in terms of\nclassical and
computable invariants of the knot. This is a joint project with Feller\,
Miller\, Nagel\, Powell\, and Ray.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lukas Lewark (Univ. Regensburg)
DTSTART:20200529T150000Z
DTEND:20200529T163000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/4
DESCRIPTION:Title: Squeezed knots\nby Lukas Lewark (Univ. Regensburg) as part of CR
M - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nA knot
is called squeezed if it is a slice of a smooth cobordism of minimal genus
between a positive knot and a negative knot. Most small knots are squeeze
d\, as are many classes of knots\, such as alternating knots. However\, Kh
ovanov homology and related tools may obstruct squeezedness. This is joint
work in progress with Peter Feller and Andrew Lobb.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ben Weinkove (Northwestern Univ.)
DTSTART:20200605T150000Z
DTEND:20200605T163000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/5
DESCRIPTION:Title: The Chern-Ricci flow\nby Ben Weinkove (Northwestern Univ.) as pa
rt of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\
nThe Chern-Ricci flow is a flow of Hermitian metrics by their Chern-Ricci
form. It generalizes the Kahler-Ricci flow to the setting of non-Kahler m
etrics on complex manifolds. I will give an overview of known results for
this flow and describe some open problems.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eiji Inoue (Tokyo Univ.)
DTSTART:20200612T150000Z
DTEND:20200612T163000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/6
DESCRIPTION:Title: mu-cscK metrics and muK-stability of polarized manifolds\nby Eij
i Inoue (Tokyo Univ.) as part of CRM - Séminaire du CIRGET / Géométrie
et Topologie\n\n\nAbstract\nI will talk about a framework unifying both th
e frameworks on "cscK metrics and K-stability of polarized manifolds" and
"Kahler-Ricci solitons and modified K-stability of Fano manifolds". There
are two divided contents as follows. \n\n1. Formulation of mu-cscK metrics
and brief remarks on results parallel to the usual canonical metrics. On
some attractive special features/phenomenon of mu-cscK metrics\; "extremal
limit" and "phase transition". On a little examples. \n\n2. How to formul
ate/derive/express mu-Futaki invariant of test configurations with general
singularities. On a counterpart of CM line bundle for muK-stability. \n\n
If time permits\, I will also propose future problems/projects and its app
lications\, especially towards the algebraic moduli problems of Fano varie
ties admitting Kahler-Ricci solitons.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Martin Bobb (UT Austin)
DTSTART:20200626T150000Z
DTEND:20200626T163000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/7
DESCRIPTION:Title: Decomposition along flats for convex projective manifolds\nby Ma
rtin Bobb (UT Austin) as part of CRM - Séminaire du CIRGET / Géométrie
et Topologie\n\n\nAbstract\nReal convex projective geometry generalizes hy
perbolic geometry in a way that allows for interesting deformation theory
and also aspects of non-positive curvature. In this talk I will introduce
convex projective geometry\, and we will discuss a natural decomposition o
f compact convex projective manifolds along their codimension-1 flat subst
ructures. This extends a celebrated 2006 result of Benoist: a 'geometric J
SJ-decomposition' for compact convex projective 3-manifolds to manifolds o
f every dimension (greater than 2).\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vaibhav Gadre (Univ. of Glasgow)
DTSTART:20200619T150000Z
DTEND:20200619T163000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/8
DESCRIPTION:Title: Statistical hyperbolicity of Teichmuller spaces\nby Vaibhav Gadr
e (Univ. of Glasgow) as part of CRM - Séminaire du CIRGET / Géométrie e
t Topologie\n\n\nAbstract\nThe notion of statistical hyperbolicity introdu
ced by Duchin-Lelievre-Mooney encapsulates whether a space is on average h
yperbolic at large scales\, that is\, whether average distance between pai
rs of points on large spheres of radius R is 2R. In this talk\, I will exp
lain how Teichmuller spaces are statistically hyperbolic with respect to s
tationary measures arising random walks on mapping class groups. This is j
oint work with Aitor Azemar and Luke Jeffreys and extends previous work of
Dowdall-Duchin-Masur.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gabriele Mondello (Univ. di Roma "Sapienza")
DTSTART:20200710T150000Z
DTEND:20200710T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/9
DESCRIPTION:Title: On spherical surfaces of genus 1 with 1 conical point\nby Gabrie
le Mondello (Univ. di Roma "Sapienza") as part of CRM - Séminaire du CIRG
ET / Géométrie et Topologie\n\n\nAbstract\nA spherical metric on a surfa
ce is a metric of constant curvature 1.\nSuch a metric has a conical point
x of angle $2\\pi\\theta$ if it has vanishing order $(\\theta-1)$ at x.\n
A spherical metric in an assigned conformal class can be viewed on one han
d as a solution of a suitable singular Liouville equation.\nOn the other h
and\, when the conformal class is not prescribed\, isotopy classes of sphe
rical metrics can be considered as flat (SO(3\,R)\,S^2)-structure\, and so
their moduli space has a natural finite-dimensional real-analytic structu
re.\n\nI will discuss recent results on the topology of such moduli space
of spherical metrics with conical points of assigned angles.\nI will then
focus on the case of genus 1 with 1 conical point.\n\nThis is joint work w
ith Eremenko-Panov and with Eremenko-Gabrielov-Panov.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicolina Istrati (Tel Aviv Univ.)
DTSTART:20200703T150000Z
DTEND:20200703T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/10
DESCRIPTION:Title: Variational problems in conformal geometry\nby Nicolina Istrati
(Tel Aviv Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et T
opologie\n\n\nAbstract\nI will present several natural functionals defined
on a conformal class of almost Hermitian metrics on a compact manifold\,
and I will establish their Euler-Lagrange equations. I will show that the
Gauduchon metrics appear naturally as the unique extremal metrics of one s
uch functional. Next\, a new class of metrics will be introduced\, also ap
pearing as extremal in complex dimension two. I will show that these new m
etrics\, while not Gauduchon in general\, give again unique representative
s\, up to constant multiples\, of conformal classes of almost Hermitian me
trics. This is joint work with D. Angella\, A. Otiman and N. Tardini.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joshua Howie (UC Davis)
DTSTART:20200717T150000Z
DTEND:20200717T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/11
DESCRIPTION:by Joshua Howie (UC Davis) as part of CRM - Séminaire du CIRG
ET / Géométrie et Topologie\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Livio Liechti (Université de Fribourg)
DTSTART:20200724T150000Z
DTEND:20200724T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/12
DESCRIPTION:Title: Divide knots of maximal genus defect\nby Livio Liechti (Univers
ité de Fribourg) as part of CRM - Séminaire du CIRGET / Géométrie et T
opologie\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrew Lobb (University of Durham\, UK)
DTSTART:20200911T150000Z
DTEND:20200911T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/13
DESCRIPTION:Title: The rectangular peg problem\nby Andrew Lobb (University of Durh
am\, UK) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\
n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carlo Scarpa (SISSA\, Italy)
DTSTART:20200918T150000Z
DTEND:20200918T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/14
DESCRIPTION:Title: The Hitchin-cscK system\nby Carlo Scarpa (SISSA\, Italy) as par
t of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\n
A classic result in the study of Kähler metrics with special curvature pr
operties is that the cscK equation can be realized as the moment map equat
ion for an infinite-dimensional Kähler reduction. We present a natural hy
perkähler extension of this moment map picture\, obtaining a new system o
f equations reminiscent of Hitchin's equations for Higgs bundles. We will
discuss some recent existence results\, particularly obstructions to solut
ions to the problem.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jonathan Johnson (University of Texas at Austin\, US)
DTSTART:20200925T150000Z
DTEND:20200925T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/15
DESCRIPTION:Title: Bi-Orderability and Pretzel Knots\nby Jonathan Johnson (Univers
ity of Texas at Austin\, US) as part of CRM - Séminaire du CIRGET / Géom
étrie et Topologie\n\n\nAbstract\nThis talk concerns the bi-orderability
of pretzel knot groups which appears to have a weird connection to the Hee
gaard Floer properties of the cyclic branched covers of the knots. In a re
cent paper\, several new examples of bi-orderable pretzel knots are found.
We\nwill discuss these results and some of their implications to this str
ange coincidence of orderability and Heegaard Floer.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Junyan Cao (Université de Nice\, France)
DTSTART:20201002T150000Z
DTEND:20201002T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/16
DESCRIPTION:Title: On the Ohsawa-Takegoshi extension theorem\nby Junyan Cao (Unive
rsité de Nice\, France) as part of CRM - Séminaire du CIRGET / Géométr
ie et Topologie\n\n\nAbstract\nSince it was established\, the Ohsawa-Takeg
oshi extension theorem turned out to be a fundamental tool in complex geom
etry. We establish a new extension result for twisted canonical forms defi
ned on a hypersurface with simple normal crossings of a projective manifol
d with a control on its L^2 norme. It is a joint work with Mihai Pãun.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christina Tonnesen-Friedman (Union College\, US)
DTSTART:20201009T150000Z
DTEND:20201009T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/17
DESCRIPTION:Title: Sasaki-Einstein metrics and the Iterated join\nby Christina Ton
nesen-Friedman (Union College\, US) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\n\nAbstract\nIn this talk\, which is based on
joint works with Charles Boyer\, I will discuss the idea of using the joi
n construction in Sasakian Geometry in a non-trivial iterative way in orde
r to arrive at some explicit Sasaki-Einstein examples in higher dimensions
.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yi Ni (Caltech\, US)
DTSTART:20201016T150000Z
DTEND:20201016T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/18
DESCRIPTION:Title: Seifert fibered surgeries on hyperbolic fibered knots\nby Yi Ni
(Caltech\, US) as part of CRM - Séminaire du CIRGET / Géométrie et Top
ologie\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aru Ray (MPIM Bonn\, Germany)
DTSTART:20201023T150000Z
DTEND:20201023T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/19
DESCRIPTION:Title: Embedding surfaces in 4-manifolds\nby Aru Ray (MPIM Bonn\, Germ
any) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\
nAbstract\nI will present a surface embedding theorem for 4-manifolds with
good fundamental group in the presence of potentially unframed\, immersed
dual spheres. The essential obstruction is the Kervaire-Milnor invariant
and a goal of the talk is to describe how it may be computed. This is base
d on joint work with Daniel Kasprowski\, Mark Powell\, and Peter Teichner.
\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hugues Auvray (Paris Orsay\, France)
DTSTART:20201030T150000Z
DTEND:20201030T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/20
DESCRIPTION:Title: Noyaux de Bergman sur les surfaces de Riemann épointées\nby H
ugues Auvray (Paris Orsay\, France) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\n\nAbstract\nDans des travaux en commun avec
X. Ma (Paris 7) et G. Marinescu (Cologne)\, nous obtenons des asymptotique
s raffinées pour des noyaux de Bergman calculées à partir de données s
ingulières. On travaille sur le complémentaire d'un nombre fini de point
s\, vus comme singularités\, dans une surface de Riemann compacte\, que l
'on munit d'une métrique étendant la métrique cusp de Poincaré autour
des singularités \; on se donne également un fibré en droites holomorph
e polarisant pour cette métrique. J'expliquerai comment une description a
vancée du modèle (sur le disque unité épointé) et des techniques de l
ocalisation dans un contexte à poids permettent de décrire les noyaux de
Bergman associés à de telles surfaces de Riemann\, et ce jusque aux sin
gularités. \n\nSi le temps le permet\, je préciserai également des inte
rprétations géométriques\, voire arithmétiques\, de tels résultats.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Philip Griffiths (Institute for Advanced Study\, University of Mia
mi)
DTSTART:20201106T160000Z
DTEND:20201106T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/21
DESCRIPTION:Title: Some geometric applications of Hodge theory\nby Philip Griffith
s (Institute for Advanced Study\, University of Miami) as part of CRM - S
éminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nModern Hodge
theory is both a subject of study in its own right and a subject that is
used in many areas of current mathematical research\, especially in but no
means restricted to algebraic geometry. This talk will be an informal and
partial overview of some of its uses with emphasis on those in algebraic
geometry. We will also discuss some of the historical development of the s
ubject\; how did it originate and how did it get to its current state? Her
e the emphasis will be on the period up until the time of Hodge and will o
nly touch on a few of the major recent milestones.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michelle Chu (University of Illinois at Chicago)
DTSTART:20201113T160000Z
DTEND:20201113T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/22
DESCRIPTION:Title: Prescribed virtual torsion in the homology of 3-manifolds\nby M
ichelle Chu (University of Illinois at Chicago) as part of CRM - Séminair
e du CIRGET / Géométrie et Topologie\n\n\nAbstract\nHongbin Sun showed t
hat a closed hyperbolic 3-manifold virtually contains any prescribed torsi
on subgroup as a direct factor in homology. In this talk we will discuss j
oint work with Daniel Groves generalizing Sun’s result to irreducible 3-
manifolds which are not graph-manifolds.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Neil Hoffman (Oklahoma State University)
DTSTART:20201120T160000Z
DTEND:20201120T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/23
DESCRIPTION:Title: Conjectures related to knot complement commensurability\nby Nei
l Hoffman (Oklahoma State University) as part of CRM - Séminaire du CIRGE
T / Géométrie et Topologie\n\n\nAbstract\nTwo manifolds $M_1$ and $M_2$
are commensurable if there is a third manifold $M_3$ that is a finite shee
ted cover of $M_1$ and $M_2$. Neumann and Reid conjecture that at most 3 h
yperbolic knot complements can be commensurable with each other. I will di
scuss what is known about the conjecture and open questions surrounding co
mmensurable knot complements.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mykola Matviichuk (McGill University)
DTSTART:20201127T160000Z
DTEND:20201127T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/25
DESCRIPTION:Title: A local Torelli theorem for log symplectic manifolds\nby Mykola
Matviichuk (McGill University) as part of CRM - Séminaire du CIRGET / G
éométrie et Topologie\n\n\nAbstract\nWe will discuss how to deform a hol
omorphic symplectic form that has logarithmic poles along a normal crossin
gs divisor. We will introduce an appropriate deformation complex and expla
in how to calculate its cohomology using natural local systems on the stra
ta of the polar divisor. An analysis of the L-infinity structure on the co
homology of the deformation complex leads to a simple combinatorial descri
ption of the deformation space in terms of the periods of the log symplect
ic form. As an application\, we construct new examples of log symplectic f
orms on $CP^4$ by deforming previously known ones. This is joint work with
Brent Pym and Travis Schedler.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matei Toma (Univ. of Nancy)
DTSTART:20201211T160000Z
DTEND:20201211T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/26
DESCRIPTION:Title: Boundedness for sets of coherent analytic sheaves\nby Matei Tom
a (Univ. of Nancy) as part of CRM - Séminaire du CIRGET / Géométrie et
Topologie\n\n\nAbstract\nA boundedness notion for sets of isomorphism clas
ses of coherent algebraic sheaves as well as a boundedness criterion were
introduced by Grothendieck in his 1961 paper on the construction of the Hi
lbert scheme. In this talk we define boundedness for coherent analytic she
aves and present a boundedness criterion in a complex geometric context. W
e then show how these apply to prove properties related to Douady spaces o
r to semistability of coherent sheaves\, such as the existence of relative
Harder-Narasimhan filtrations.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mario Garcia-Fernandez (ICMAT\, Madrid)
DTSTART:20210115T160000Z
DTEND:20210115T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/27
DESCRIPTION:Title: Gravitating vortices with positive curvature\nby Mario Garcia-F
ernandez (ICMAT\, Madrid) as part of CRM - Séminaire du CIRGET / Géomét
rie et Topologie\n\n\nAbstract\nIn this talk I will overview recent joint
work with Vamsi \nPingali and Chengjian Yao in arXiv:1911.09616 about grav
itating \nvortices. These equations couple a K\\"ahler metric on a compact
\nRiemann surface with a hermitian metric over a holomorphic line bundle
\nequipped with a fixed global section --- the Higgs field ---\, and have
\na symplectic interpretation as moment-map equations.\n\nIn our work we g
ive a complete solution to the existence problem for \ngravitating vortice
s on the Riemann sphere with positive topological \nconstant c > 0. Our ma
in result establishes the existence of solutions \nprovided that a GIT sta
bility condition for an effective divisor on \nCP^1 is satisfied. To this
end\, we use a continuity path starting from \nYang's solution with c = 0.
A salient feature of our argument is a new \nbound S \\geq c for the curv
ature of gravitating\nvortices\, which we apply to construct a limiting so
lution along the \npath via Cheeger-Gromov theory.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simone Diverio (SAPIENZA Università di Roma)
DTSTART:20210205T160000Z
DTEND:20210205T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/28
DESCRIPTION:Title: Pointwise universal Gysin formulae and positivity of some character
istic forms\nby Simone Diverio (SAPIENZA Università di Roma) as part
of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIn
the last few years there has been a renewed interest around an old conjec
ture by Griffiths characterizing which should be the positive characterist
ic forms for any given Griffiths positive holomorphic Hermitian vector bun
dle. According to this conjecture\, they should be precisely the character
istic forms belonging to the positive cone spanned by the Schur forms.\nAf
ter recalling the various notions of positivity for holomorphic Hermitian
vector bundles\, and how they are (or should be) related\, we shall explai
n a recent result obtained in collaboration with my PhD student F. Fagioli
\, which gives a partial confirmation of the above conjecture.\nSuch a res
ult is obtained as a consequence of a pointwise\, differential-geometric G
ysin formula for the push-forward of the curvature of the tautological lin
e bundles over flag bundles.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yohan Brunebarbe (Univ. of Bordeaux)
DTSTART:20210122T160000Z
DTEND:20210122T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/29
DESCRIPTION:Title: Higher-dimensional Arakelov inequalities and applications to hyperb
olicity\nby Yohan Brunebarbe (Univ. of Bordeaux) as part of CRM - Sém
inaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIn this talk\,
I will introduce the so-called Arakelov inequalities (due to Arakelov\, Fa
ltings\, Peters\, Deligne\, etc.) that one gets from an abelian scheme or
more generally from a variation of Hodge structures on a curve. I will the
n discuss a generalization of these inequalities to higher-dimensional bas
is\, and explain how they can be used to prove hyperbolicity properties of
some moduli spaces of varieties.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tarik Aougab (Haverford College)
DTSTART:20210129T160000Z
DTEND:20210129T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/30
DESCRIPTION:Title: Statistics for random curves on surfaces\nby Tarik Aougab (Have
rford College) as part of CRM - Séminaire du CIRGET / Géométrie et Topo
logie\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Allison Miller (Rice University)
DTSTART:20210212T160000Z
DTEND:20210212T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/31
DESCRIPTION:Title: Amphichiral knots with large 4-genera\nby Allison Miller (Rice
University) as part of CRM - Séminaire du CIRGET / Géométrie et Topolog
ie\n\n\nAbstract\nAn oriented knot is called negative amphichiral if it is
isotopic to the reverse of its mirror image. Such knots have order at mos
t two in the concordance group\, and many modern concordance invariants va
nish on them. Nevertheless\, we will see that there are negative amphichir
al knots with arbitrarily large 4-genera\, using Casson-Gordon signature i
nvariants as a primary tool.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michael Hallam (Oxford University)
DTSTART:20210219T160000Z
DTEND:20210219T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/32
DESCRIPTION:Title: Stability of fibrations through geodesic analysis\nby Michael H
allam (Oxford University) as part of CRM - Séminaire du CIRGET / Géomét
rie et Topologie\n\n\nAbstract\nA celebrated result in geometry is the Kob
ayashi--Hitchin correspondence\, which states that a holomorphic vector bu
ndle on a compact Kähler manifold admits a Hermite--Einstein metric if an
d only if the bundle is slope polystable. Recently\, Dervan and Sektnan ha
ve conjectured an analogue of this correspondence for fibrations whose fib
res are compact Kähler manifolds admitting Kähler metrics of constant sc
alar curvature. Their conjecture is that such a fibration is polystable in
a suitable sense\, if and only if it admits an optimal symplectic connect
ion. In this talk\, I will provide an introduction to this theory\, and de
scribe my recent work on the conjecture. Namely\, I show that existence of
an optimal symplectic connection implies polystability with respect to a
large class of fibration degenerations. The techniques used involve analys
ing geodesics in the space of relatively Kähler metrics of fibrewise cons
tant scalar curvature\, and convexity of the log-norm functional in this s
etting. This is work for my PhD thesis\, supervised by Ruadhaí Dervan and
Frances Kirwan.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anthony Conway (MIT)
DTSTART:20210312T160000Z
DTEND:20210312T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/33
DESCRIPTION:Title: Knotted surfaces with infinite cyclic knot group\nby Anthony Co
nway (MIT) as part of CRM - Séminaire du CIRGET / Géométrie et Topologi
e\n\n\nAbstract\nThis talk will concern embedded surfaces in 4-manifolds f
or which the fundamental group of the complement is infinite cyclic. Worki
ng in the topological category\, necessary and sufficient conditions will
be given for two such surfaces to be isotopic. This is based on joint work
with Mark Powell.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Kottke (New College of Florida)
DTSTART:20210226T160000Z
DTEND:20210226T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/34
DESCRIPTION:Title: Bigerbes and applications\nby Chris Kottke (New College of Flor
ida) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\
nAbstract\nGerbes are geometric objects on a space which represent degree
3 integer cohomology\, in the same way that complex line bundles (classifi
ed by the Chern class) represent cohomology in degree 2. Among other setti
ngs\, they arise naturally as obstructions to lifting the structure group
of a principal G-bundle to a U(1) central extension of G. \nHigher version
s of gerbes\, representing cohomology classes of degree 4 and up\, are typ
ically complicated by higher categorical concepts (2-morphisms and so on)
in their definition. In contrast\, bigerbes (and their higher cousins) adm
it a simple\, geometric\, non-higher-categorical description\, and provide
a satisfactory account of the relationship between so-called `string stru
ctures' on a manifold and `fusion spin structures' on its loop space\, amo
ng other applications. This is based on recent joint work with Richard Mel
rose.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Philipp Naumann (Univ of Bayreuth)
DTSTART:20210319T160000Z
DTEND:20210319T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/35
DESCRIPTION:Title: Curvature formula for direct images of relative canonical bundles w
ith a Poincaré type twist\nby Philipp Naumann (Univ of Bayreuth) as p
art of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nAbstract:
TBA\n\nWe give a curvature formula of the L^2 metric on the direct image o
f the relative canonical bundle twisted by a holomorphic line bundle endow
ed with a positive singular metric whose inverse has Poincaré type singul
arities along a relative snc divisor. The result applies to families of lo
g canonically polarized pairs. Moreover\, we show that it improves the gen
eral positivity result of Berndtsson-Paun in a special situation of a big
line bundle.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Antonio Alfieri (University of British Columbia)
DTSTART:20210326T150000Z
DTEND:20210326T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/36
DESCRIPTION:Title: Symmetric knots and Floer homologies\nby Antonio Alfieri (Unive
rsity of British Columbia) as part of CRM - Séminaire du CIRGET / Géomé
trie et Topologie\n\n\nAbstract\nI will discuss some open problems\, and s
urvey some classical material regarding symmetric knots\, and group action
s on 3- and 4-manifolds. In the second part of the talk I will discuss how
techniques from Floer theory can be employed to approach some of these pr
oblems. Part of this is joint work with Irving Dai\, Abhishek Mallick\, an
d Sungkyung Kang.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tye Lidman (North Carolina State University)
DTSTART:20210507T150000Z
DTEND:20210507T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/37
DESCRIPTION:Title: SU(2) representations for toroidal homology spheres\nby Tye Lid
man (North Carolina State University) as part of CRM - Séminaire du CIRGE
T / Géométrie et Topologie\n\n\nAbstract\nThe three-dimensional Poincare
conjecture shows that any closed three-manifold other than the three-sphe
re has non-trivial fundamental group. A natural question is how to measure
the non-triviality of such a group\, and conjecturally this can be concre
tely realized by a non-trivial representation to SU(2). We will show that
the fundamental groups of three-manifolds with incompressible tori admit n
on-trivial SU(2) representations. This is joint work with Juanita Pinzon-C
aicedo and Raphael Zentner.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Johnny Nicholson (UCL)
DTSTART:20210423T150000Z
DTEND:20210423T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/38
DESCRIPTION:Title: Projective modules and exotic group presentations\nby Johnny Ni
cholson (UCL) as part of CRM - Séminaire du CIRGET / Géométrie et Topol
ogie\n\n\nAbstract\nTwo presentations for a group G which have the same de
ficiency are called exotic if the corresponding presentation complexes are
not homotopy equivalent. The first examples of exotic presentations were
found by Dunwoody and Metzler in the 1970s but\, owing to the difficulty o
f the algebra involved\, few other examples have since been found.\nIn thi
s talk\, I will discuss a class of finite groups G for which these algebra
ic difficulties can be largely reduced to a question about projective ZG m
odules which we resolve. I will also discuss applications to Wall’s D2 p
roblem and the classification of 4-manifolds.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Marengon (Max Planck Institute for Mathematics)
DTSTART:20210409T150000Z
DTEND:20210409T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/39
DESCRIPTION:Title: Relative genus bounds in indefinite 4-manifolds\nby Marco Maren
gon (Max Planck Institute for Mathematics) as part of CRM - Séminaire du
CIRGET / Géométrie et Topologie\n\n\nAbstract\nGiven a closed 4-manifold
X with an indefinite intersection form\, we consider smoothly embedded su
rfaces in X-int(B^4)\, with boundary a given knot K in the 3-sphere.\nWe g
ive several methods to bound the genus of such surfaces in a fixed homolog
y class. Our techniques include adjunction inequalities from Heegaard Floe
r homology and the Bauer-Furuta invariants\, and the 10/8 theorem.\nIn par
ticular\, we present obstructions to a knot being H-slice (that is\, bound
ing a null-homologous disc) in a 4-manifold and show that the set of H-sli
ce knots can detect exotic smooth structures on closed 4-manifolds.\nThis
is joint work with Ciprian Manolescu and Lisa Piccirillo.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Wenhao Ou (Chinese Academy of Science)
DTSTART:20210430T150000Z
DTEND:20210430T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/41
DESCRIPTION:Title: Projective varieties whose tangent bundle contains certain positivi
ty / Variétés projectives dont le fibré tangent contient certaine posit
ivité\nby Wenhao Ou (Chinese Academy of Science) as part of CRM - Sé
minaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nSince the Fran
kel conjecture and the Hartshorne conjecture\, it turns out that the posit
ivity of tangent bundle imposes geometric constraints on the ambient manif
old. In this talk\, I will introduce some classic results and my recent wo
rks on these structural theorems.\n\nDepuis la conjecture de Frankel et la
conjecture de Hartshorne\, il se trouve que la positivité du fibré tang
ent impose des contraintes géométriques sur la variété ambiante. Dans
cet exposé\, je vais introduire des résultats classiques et mes travaux
récents sur ce genre de théorèmes structurels.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ziwen Zhu (Peking University)
DTSTART:20210514T150000Z
DTEND:20210514T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/42
DESCRIPTION:Title: Equivariant K-stability and valuative criteria\nby Ziwen Zhu (P
eking University) as part of CRM - Séminaire du CIRGET / Géométrie et T
opologie\n\n\nAbstract\nEquivariant K-stability of Fano varieties is defin
ed via equivariant test configurations. By definition it is weaker than us
ual K-stability. However\, for Fano varieties with large symmetry\, it is
often easier to check equivariant K-stability. Valuative criterion is deve
loped by Chi Li and Kento Fujita to characterize K-stability using valuati
ons. In this talk\, I will show that there is a parallel theory for equiva
riant K-stability by introducing pseudovaluations. As an application\, I w
ill discuss how it can be applied to study K-stability of Fano varieties u
nder finite group action. The talk is partially based on joint work with Y
uchen Liu.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alix Deruelle (Sorbonne Université)
DTSTART:20210917T150000Z
DTEND:20210917T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/43
DESCRIPTION:Title: A relative entropy for expanders of the Ricci flow (joint work with
Felix Schulze\, Warwick University)\nby Alix Deruelle (Sorbonne Unive
rsité) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n
\n\nAbstract\nExpanding self-similar solutions of the Ricci flow are solut
ions which evolve by scaling and diffeomorphisms only. Such solutions are
also called expanding gradient Ricci solitons. These "canonical" metrics a
re potential candidates for smoothing out isolated singularities instantan
eously. These heuristics apply to the Kähler-Ricci flow too. In this talk
\, we ask the question of uniqueness of such self-similar solutions coming
out of a given metric cone over a smooth link. As a first step\, we make
sense of a suitable Lyapunov functional also called relative entropy in th
is setting.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xuwen Zhu (Northeastern University)
DTSTART:20210924T150000Z
DTEND:20210924T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/44
DESCRIPTION:Title: Constant curvature conical metrics\nby Xuwen Zhu (Northeastern
University) as part of CRM - Séminaire du CIRGET / Géométrie et Topolog
ie\n\n\nAbstract\nThe problem of finding and classifying constant curvatur
e metrics with conical singularities has a long history bringing together
several different areas of mathematics. This talk will focus on the partic
ularly difficult spherical case where many new phenomena appear. When some
of the cone angles are bigger than $2\\pi$\, uniqueness fails and existen
ce is not guaranteed\; smooth deformation is not always possible and the m
oduli space is expected to have singular strata. I will give a survey of s
everal recent results regarding this singular uniformization problem\, con
necting microlocal techniques with complex analysis and synthetic geometry
. Based on joint works with Rafe Mazzeo\, Bin Xu\, and Mikhail Karpukhin.\
n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Peter Feller (ETH Zurich)
DTSTART:20211015T150000Z
DTEND:20211015T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/45
DESCRIPTION:Title: Braids\, quasimorphisms\, and slice-Bennequin inequalities\nby
Peter Feller (ETH Zurich) as part of CRM - Séminaire du CIRGET / Géomé
trie et Topologie\n\n\nAbstract\nThe writhe of a braid (=#pos crossing - #
neg crossings) and the fractional Dehn twist coefficient of a braid (a rat
ional number that measures "how much the braid twists") are the two most p
rominent examples of what is known as a quasimorphism (a map that fails to
be a group homomorphism by at most a bounded amount) from Artin's braid g
roup on n-strands to the reals. We consider characterizing properties for
such quasimorphisms and talk about relations to the study of knot concorda
nce. For the latter\, we consider inequalities for quasimorphisms modelled
after the so-called slice-Bennequin inequality: writhe(B) <= 2g_4(K) - 1
+ n for all n-stranded braids B with closure a knot K. Based on work in pr
ogress.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yang Li (MIT)
DTSTART:20211022T150000Z
DTEND:20211022T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/46
DESCRIPTION:Title: Metric SYZ conjecture\nby Yang Li (MIT) as part of CRM - Sémin
aire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nI will discuss my
recent work on the metric aspect of the Strominger-Yau-Zaslow conjecture\
, focusing mostly on the Fermat family of hypersurfaces. The conjecture as
ks for the existence of special Lagrangian torus fibrations for Calabi-Yau
manifolds near the large complex structure limit\, at least in the generi
c region of the manifold. The key is to prove a metric asymptote in the li
mit\, and time permitting I will try to mention some ingredients.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Golla (University of Nantes)
DTSTART:20211029T150000Z
DTEND:20211029T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/47
DESCRIPTION:Title: 3-manifolds that bound no definite 4-manifold\nby Marco Golla (
University of Nantes) as part of CRM - Séminaire du CIRGET / Géométrie
et Topologie\n\n\nAbstract\nAll 3-manifolds bound 4-manifolds\, and many c
onstructions of 3-manifolds automatically come with a 4-manifold bounding
it. Oftentimes these 4-manifolds have definite intersection form. Using He
egaard Floer correction terms and an analysis of short characteristic cove
ctors in bimodular lattices\, we give an obstruction for a 3-manifold to b
ound a definite 4-manifold\, and produce some concrete examples. This is j
oint work with Kyle Larson.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ruadhai Dervan (University of Cambridge)
DTSTART:20211112T160000Z
DTEND:20211112T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/48
DESCRIPTION:Title: Stability conditions for polarised varieties\nby Ruadhai Dervan
(University of Cambridge) as part of CRM - Séminaire du CIRGET / Géomé
trie et Topologie\n\n\nAbstract\nA central theme of complex geometry is th
e relationship between differential-geometric PDEs and algebro-geometric n
otions of stability. Examples include Hermitian Yang-Mills connections and
Kähler-Einstein metrics on the PDE side\, and slope stability and K-stab
ility on the algebro-geometric side. I will describe a general framework a
ssociating geometric PDEs on complex manifolds to notions of stability\, a
nd will sketch a proof showing that existence of solutions is equivalent t
o stability in a model case. The framework can be seen as an analogue in t
he setting of varieties of Bridgeland's stability conditions on triangulat
ed categories.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ya Deng (CNRS\, Université de Lorraine)
DTSTART:20211119T160000Z
DTEND:20211119T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/49
DESCRIPTION:Title: Big Picard theorem for varieties admitting nilpotent harmonic bundl
es\nby Ya Deng (CNRS\, Université de Lorraine) as part of CRM - Sémi
naire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nThe big Picard t
heorem states that any holomorphic map from the punctured disk into the Ri
emann sphere avoiding three points must extend across the origin. In this
talk I will explain a generalized big picard theorem for quasi-compact Kä
hler manifolds U endowed with a nilpotent harmonic bundle whose Higgs fiel
d is injective at one point. Moreover\, we prove that there is a finite u
nramified cover V of U from a quasi-projective manifold V so that the big
Picard theorem holds for any projective compactification of V. This work i
s based on the joint work with Benoit Cadorel.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/49/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gilles Carron (Université de Nantes)
DTSTART:20211126T160000Z
DTEND:20211126T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/50
DESCRIPTION:Title: Kato's Limits\nby Gilles Carron (Université de Nantes) as part
of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nI
t is a joint work with I. Mondello (Paris XII) and D. Tewodrose (UL Bruxel
les\, Nantes). A Kato bound on the Ricci curvature yields nice geometric p
roperties ( eigenvalue lower bound\, heat kernel estimates...)\; in partic
ular it implies a doubling condition for the Riemannian volume and hence a
precompactness result in the Gromov-Hausdorff topology. We have obtained
results that are generalization of the ones of Cheeger and Colding (where
a uniform lower bound on the Ricci curvature is assumed).\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/50/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nathan Grieve (RMC/Carleton/UQAM)
DTSTART:20211210T160000Z
DTEND:20211210T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/51
DESCRIPTION:Title: On topics that surround the Cone Theorem\, K-stability and Diophant
ine Arithmetic Geometry\nby Nathan Grieve (RMC/Carleton/UQAM) as part
of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nI
will survey concepts that are near to the Cone Theorem and MMP (for klt pa
irs)\, the question of K-stability for polarized projective varieties and
their Diophantine arithmetic consequences. In doing so\, I will report on
some recent and ongoing work. As one example\, I intend to propose a con
cept of slope stability\, for polarized projective varieties\, from the vi
ewpoint of the extremal ray theory. The idea is that it should extend the
traditional concept of slope stability\, which is measured along a subvar
iety.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sucharit Sarkar (UCLA)
DTSTART:20211105T153000Z
DTEND:20211105T164500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/52
DESCRIPTION:Title: Mixed invariants in Khovanov homology for unorientable cobordisms\nby Sucharit Sarkar (UCLA) as part of CRM - Séminaire du CIRGET / Géo
métrie et Topologie\n\n\nAbstract\n** Note : the event will take place at
11.30 am and not 11 am as usual.\n** Attention : l'horaire est modifié
à 11.30 exceptionnellement.\n\nUsing Bar-Natan's and Lee's deformations o
f Khovanov homology of links\, we define minus\, plus\, and infinity versi
ons of Khovanov homology. Given an unorientable cobordism in [0\,1]\\times
S^3 from a link L_0 to a link L_1\, we define a mixed invariant as a map
from the minus version of the Khovanov homology of L_0 to the plus version
of the Khovanov homology of L_1. The construction is similar to the mixed
invariant in Heegaard Floer homology. This invariant can be used to disti
nguish exotic cobordisms\, that is\, two cobordisms which are topologicall
y isotopic but not smoothly isotopic. This is joint with Robert Lipshitz.\
n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adam Jacob (University of California Davis)
DTSTART:20211217T160000Z
DTEND:20211217T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/53
DESCRIPTION:Title: Special Lagrangian torus fibrations on Del Pezzo and Rational Ellip
tic Surfaces\nby Adam Jacob (University of California Davis) as part o
f CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIn
this talk I will demonstrate the construction of mirror special Lagrangian
torus fibrations on two non-compact spaces: A Del Pezzo surface with a sm
ooth anticanonical divisor removed\, and a rational elliptic surface minus
a singular fiber of Kodaira type I_k. Special emphasis will be given to l
ocal geometric models\, and how the mean curvature flow provides a key ste
p in the construction. This is joint work with T.C. Collins and Y.-S. Lin\
n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Steven Sivek (Imperial College)
DTSTART:20211203T160000Z
DTEND:20211203T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/54
DESCRIPTION:by Steven Sivek (Imperial College) as part of CRM - Séminaire
du CIRGET / Géométrie et Topologie\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ethan Addison (Notre Dame Univ.)
DTSTART:20220114T160000Z
DTEND:20220114T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/55
DESCRIPTION:Title: Generalizing Poincaré-Type Kähler Metrics\nby Ethan Addison (
Notre Dame Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et T
opologie\n\n\nAbstract\nPoincaré-type metrics are a type of complete cusp
metric defined on the complement of a complex hypersurface $X$ in an ambi
ent manifold\, yet a result by Auvray shows that constant scalar curvature
metrics of Poincaré-type always split into a product of cscK metrics in
each of the ends\, inducing a cscK metric on $X$. We prove a result about
\\emph{gnarled} Poincaré-type metrics using holomorphic flows on $X$ to c
onstruct complete cscK metrics near the ends which are perturbations of cs
cK Poincaré-type metrics\, even when the induced perturbed Kähler class
on $X$ does not admit a cscK metric\, thus generalizing the initial flavor
of metric to one with fewer restrictions.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Francesco Lin (Columbia Univ.)
DTSTART:20220121T160000Z
DTEND:20220121T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/56
DESCRIPTION:Title: Closed geodesics and Frøyshov invariants of hyperbolic three-manif
olds\nby Francesco Lin (Columbia Univ.) as part of CRM - Séminaire du
CIRGET / Géométrie et Topologie\n\n\nAbstract\nFrøyshov invariants are
subtle numerical topological invariants of rational homology three-spher
es derived from gradings in monopole Floer homology. In this talk I will
look at their relation with invariants arising from hyperbolic geometry (
such as volumes and lengths of closed geodesics)\, using an odd version o
f the Selberg trace formula and ideas from analytic number theory. In par
ticular\, for the class of minimal L-spaces\, I will describe an effectiv
e procedure to compute them taking as input explicit geometric data\, and
show for example how this can be used to determine all the Frøyshov in
variants for the Seifert-Weber dodecahedral space. This is joint work wit
h M. Lipnowski (McGill).\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xi Sisi Shen (Columbia Univ.)
DTSTART:20220128T160000Z
DTEND:20220128T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/57
DESCRIPTION:Title: A Chern-Calabi flow on Hermitian Manifolds\nby Xi Sisi Shen (Co
lumbia Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topol
ogie\n\n\nAbstract\nWe discuss the existence problem of constant Chern sca
lar curvature metrics on a compact complex manifold and introduce a Hermit
ian analogue of the Calabi flow on compact complex manifolds with vanishin
g first Bott-Chern class.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/57/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kyle Hayden (Columbia Univ.)
DTSTART:20220211T160000Z
DTEND:20220211T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/59
DESCRIPTION:Title: Where are the complex curves in Khovanov homology?\nby Kyle Hay
den (Columbia Univ.) as part of CRM - Séminaire du CIRGET / Géométrie e
t Topologie\n\n\nAbstract\nSince the advent of gauge theory\, many modern
tools exhibit a close connection with complex curves and a heightened sens
itivity to objects from the complex realm. Surprisingly\, this is true eve
n for Khovanov homology\, whose construction is combinatorial rather than
geometric. I will discuss this in the context of joint work with Isaac Sun
dberg that uses Khovanov homology to study knotted surfaces in 4-space\, e
specially (compact pieces of) complex curves in the 4-ball.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/59/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ruiran Sun (UQAM)
DTSTART:20220218T160000Z
DTEND:20220218T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/60
DESCRIPTION:by Ruiran Sun (UQAM) as part of CRM - Séminaire du CIRGET / G
éométrie et Topologie\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/60/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Louis Ioos (Max Planck Institute\, Bonn)
DTSTART:20220311T160000Z
DTEND:20220311T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/61
DESCRIPTION:Title: Quantization methods in the Yau-Tian-Donaldson program\nby Loui
s Ioos (Max Planck Institute\, Bonn) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\n\nAbstract\nA celebrated conjecture of Yau
states that the existence of a Kähler metric\nwith constant scalar curvat
ure on a projective manifold should be equivalent to a purely\nalgebraic s
tability condition. Much progress has been done on this conjecture in the\
npast decades\, culminating in what is now called the Yau-Tian-Donaldson p
rogram.\nIn this talk\, I will explain the key role played by quantization
methods in this program\,\nand how they can be improved using a semiclass
ical estimate of the quantum noise of\nBerezin-Toeplitz quantization. This
is partly based on joint works in collaboration with\nVictoria Kaminker\,
Leonid Polterovich and Dor Shmoish.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/61/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jacob Caudell (Boston College)
DTSTART:20220225T160000Z
DTEND:20220225T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/62
DESCRIPTION:Title: Lens space surgeries\, lattices\, and the Poincaré homology sphere
.\nby Jacob Caudell (Boston College) as part of CRM - Séminaire du CI
RGET / Géométrie et Topologie\n\nAbstract: TBA\n\nMoser's classification
of Dehn surgeries on torus knots (1971) inspired a now fifty-years-old pr
oject to classify "exceptional" Dehn surgeries on knots in the three-spher
e. A prominent component of this project seeks to classify which knots adm
it surgeries to the "simplest" non-trivial 3-manifolds--lens spaces. By co
mbining data from Floer homology and the theory of integer lattices into t
he notion of a changemaker lattice\, Greene (2010) solved the lens space r
ealization problem: every lens space which may be realized as surgery on a
knot in the three-sphere may be realized by a knot already known to surge
r to that lens space (i.e. a Berge knot). In this talk\, we present a surv
ey of techniques in Dehn surgery and their applications\, introduce a latt
ice theoretic construction in the spirit of Greene's changemaker lattices\
, and discuss applications to surgeries on knots in the Poincaré homology
sphere.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/62/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alan Reid (Rice University)
DTSTART:20220401T150000Z
DTEND:20220401T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/63
DESCRIPTION:Title: Embedding and bounding geometrically rational homology 3-spheres\nby Alan Reid (Rice University) as part of CRM - Séminaire du CIRGET /
Géométrie et Topologie\n\n\nAbstract\nBordism properties of closed manif
olds have been a classical and important topic in topology\; for example i
t is a classical result of Rohklin that all closed orientable 3-manifolds
bound a compact 4-manifold. In the context of hyperbolic manifolds\, a na
tural geometric version of bordism is that of bounding geometrically: name
ly whether a connected closed orientable hyperbolic n-manifold M could ar
ise as the totally geodesic boundary of a compact hyperbolic (n+1)-manifol
d W. In work with Long (from 2000) we showed that there are infinitely ma
ny closed orientable hyperbolic n-manifolds that bound geometrically. One
feature of our construction is that all examples produced in dimension
3 have b_1>0. This led to the question of whether there are rational homo
logy 3-spheres that bound geometrically. In this talk we describe a constr
uction of infinitely many such rational homology 3-spheres.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/63/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Allison Moore (Virginia Commonwealth)
DTSTART:20220408T150000Z
DTEND:20220408T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/64
DESCRIPTION:Title: Cosmetic surgery\, cosmetic crossings\nby Allison Moore (Virgin
ia Commonwealth) as part of CRM - Séminaire du CIRGET / Géométrie et To
pologie\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/64/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexandre Girouard (Université de Laval)
DTSTART:20220422T150000Z
DTEND:20220422T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/65
DESCRIPTION:Title: Steklov eigenvalues\, homogenization and free boundary minimal surf
aces\nby Alexandre Girouard (Université de Laval) as part of CRM - S
éminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIt has been
known since classical antiquity that disks have the largest area among pla
nar figures of prescribed perimeter. Nevertheless\, a rigorous proof was o
nly given around the end of the 19th century. During the 20th century\, ar
ea and perimeter were replaced by many other analytic and geometric quanti
ties\, and the geometric setting has been vastly enlarged. In this talk we
will be interested in two such isoperimetric-type problems:\n\n(A) Free b
oundary minimal surfaces\nThe minimization of area for surfaces in balls\,
with their boundary that are constrained to live on the boundary sphere (
free boundary minimal surfaces).\n\nB) Isoperimetric problem for Steklov e
igenvalues\nThe maximization of the spectral gap of Dirichlet-to-Neumann o
perators for surfaces with prescribed perimeter.\n\nFor domains in the uni
t sphere and planar domains\, I will describe the complete solution of pro
blem (B). It is based on the theory of homogenization by perforation\, a t
opic which comes from applied and industrial mathematics. Then\, using wor
k of Fraser and Schoen\, I will show how this solution leads to the constr
uction of new free boundary minimal surfaces in the unit 3-ball that have
area larger than was previously thought possible.\n\nThis talk is based on
joint work with Antoine Henrot\, Mikhail Karpukhin and Jean Lagacé.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/65/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jean-Philippe Burelle (Univ. de Sherbrooke)
DTSTART:20220429T150000Z
DTEND:20220429T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/66
DESCRIPTION:Title: Piecewise circular curves and flag positivity.\nby Jean-Philipp
e Burelle (Univ. de Sherbrooke) as part of CRM - Séminaire du CIRGET / G
éométrie et Topologie\n\n\nAbstract\nIn this joint work with Ryan Kirk\,
we investigate moduli spaces of closed piecewise circular curves. A curve
is piecewise circular if it is made of pieces which are circular arcs\, a
nd these arcs are tangent at the intersection of pieces. We identify a spe
cial connected component of these moduli spaces and prove that it is homeo
morphic to an open ball of dimension 2n-10. We characterize this component
as the subset of curves which have decreasing curvature in an appropriate
sense. The proof involves "Lie circle geometry"\, a somewhat out of fashi
on theory of the homogeneous spaces of Sp(4\,R)\, and Lusztig-Fock-Gonchar
ov positivity.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/66/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joel Kamnitzer (University of Toronto)
DTSTART:20220506T150000Z
DTEND:20220506T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/67
DESCRIPTION:Title: Symplectic duality and affine Grassmannian slices\nby Joel Kamn
itzer (University of Toronto) as part of CRM - Séminaire du CIRGET / Géo
métrie et Topologie\n\n\nAbstract\nSymplectic resolutions are an exciting
new frontier of research in geometry and representation theory. One of t
he most fascinating aspects of this study is symplectic duality: the obser
vation that these resolutions come in pairs with matching properties. The
Coulomb\nbranch construction allows us to produce and study many of these
dual pairs. I will attempt to survey recent work in this area\, particu
larly focusing on ADE quiver varieties and affine Grassmannian slices.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/67/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aldo Witte (KU Leuven)
DTSTART:20220527T150000Z
DTEND:20220527T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/68
DESCRIPTION:Title: Singular fibrations in toric and Poisson geometry\nby Aldo Witt
e (KU Leuven) as part of CRM - Séminaire du CIRGET / Géométrie et Topol
ogie\n\n\nAbstract\nIn this talk I will present a class of singular fibrat
ions called boundary Lefschetz fibrations. These play important roles in t
he\, quite different\, fields of semi-toric and generalized complex geomet
ry. After describing how they can be studied using Lie algebroids\, I will
show that they behave well with respect to blow-ups and connected sums. Fi
nally\, I will show how they can be used in extending T-duality\, a versio
n of mirror symmetry. Joint work with Gil Cavalcanti and Ralph Klaasse.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/68/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eric Finster (University of Birmingham)
DTSTART:20220902T150000Z
DTEND:20220902T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/70
DESCRIPTION:Title: Homotopy Theory and Constructive Mathematics\nby Eric Finster (
University of Birmingham) as part of CRM - Séminaire du CIRGET / Géomét
rie et Topologie\n\n\nAbstract\nConstructive mathematicians and computer s
cientists have long been\ninterested in logical theories in which all math
ematical statements\nhave computational content. In such systems\, any pr
oof of the\nexistence of some natural number automatically gives an algori
thm for\ncomputing the number. Most modern computer "proof assistants"\,
that\nis\, programs aimed at helping the user construct and verify the\nco
rrectness of mathematical statements\, are based on a class of such\nsyste
ms call *type theories*.\n\nAround 15 years ago\, however\, it was discove
red that the way type\ntheories represent equality meant that\, rather tha
n describing\nconstructive *sets*\, these systems should more properly be
thought of\nas describing constructive *homotopy types*. This has led to
a number\nof new connections between homotopy theory\, higher category the
ory\,\ncomputer science and logic. In this talk\, I will describe some of
\nthese ideas and the results that they have led to.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/70/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ruiran Sun (CIRGET)
DTSTART:20220923T150000Z
DTEND:20220923T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/71
DESCRIPTION:Title: On slope and valuative K-semistability for big and nef birational d
ivisors\nby Ruiran Sun (CIRGET) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/71/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mathieu Anel (Carnegie Mellon University)
DTSTART:20220930T150000Z
DTEND:20220930T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/72
DESCRIPTION:Title: Introduction to non-separated topology\nby Mathieu Anel (Carneg
ie Mellon University) as part of CRM - Séminaire du CIRGET / Géométrie
et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nClassically a topolo
gical space has a set of points. But non-separated spaces (Shrinking Kahler-Ricci solitons\nby Ronan Conlan (University of
Texas at Dallas) as part of CRM - Séminaire du CIRGET / Géométrie et T
opologie\n\nLecture held in PK-5115.\n\nAbstract\nShrinking Kahler-Ricci s
olitons model finite-time singularities of the Kahler-Ricci flow\, hence t
he need for their classification. I will talk about the classification of
such solitons in 4 real dimensions. This is joint work with Bamler-Cifarel
li-Deruelle\, Cifarelli-Deruelle\, and Deruelle-Sun.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/73/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Carlo Scarpa (CIRGET)
DTSTART:20221014T150000Z
DTEND:20221014T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/74
DESCRIPTION:Title: Scalar curvature and deformations of complex structures\nby Car
lo Scarpa (CIRGET) as part of CRM - Séminaire du CIRGET / Géométrie et
Topologie\n\nLecture held in PK-5115.\n\nAbstract\nA classical problem in
Kähler geometry is to choose\, among all the possible Kähler metrics on
a manifold\, a canonical representative of each Kähler class. This is usu
ally done by imposing curvature conditions on the metric\, such as Ricci-f
lat\, Kähler-Einstein\, or constant scalar curvature. In this talk\, I wi
ll describe how the problem changes when we also consider deformations of
the complex structure\, introducing a partial differential equation which
gives a canonical choice of a Kähler metric for each deformation class. T
ime permitting\, I will examine the case of toric manifolds in more detail
. The talk is based on arxiv:2202.00429 and joint work with J. Stoppa.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/74/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Georg Biedermann (Universidad del Norte)
DTSTART:20221021T150000Z
DTEND:20221021T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/75
DESCRIPTION:Title: Calculus in homotopy theory\nby Georg Biedermann (Universidad d
el Norte) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie
\n\nLecture held in PK-5115.\n\nAbstract\n(joint with M. Anel\, E. Finster
and A. Joyal)\nIn classical calculus one studies smooth functions via the
ir Taylor series. Its $n$-th homogeneous layer is governed by a single coe
fficient: the $n$-th derivative. As part of his effort to relate algebraic
K-theory to topological cyclic homology Goodwillie during the 90s introdu
ced "Goodwillie calculus" to homotopy theory. A homotopy invariant functor
is viewed as an analogue of a smooth function and resolved into a tower w
hose $n$-th homogeneous layer is governed by a single coefficient: a spect
rum (in the sense of homotopy theory) with $\\Sigma_n$-action. Goodwillie
calculus is now a central tool in homotopy theory.\nAround the same time (
and influenced by Goodwillie) Michael Weiss constructed "orthogonal calcul
us": space-valued functors from the category of finite dimensional Euclide
an vector spaces with morphism given by Stiefel manifolds are resolved int
o an orthogonal tower whose $n$-th homogeneous layer is governed by a spec
trum with an action by $O(n)$. Weiss' theory has found many applications i
n differential topology.\nPeople have wondered for a long time whether bot
h theories have a common description. We can give one. In fact\, it turns
out that the theory of $\\infty$-topoi is the perfect language. For any le
ft exact localization $L$ of an $\\infty$-topos we construct a tower $(P_n
)_{n\\ge 0}$ of left exact localizations such that $P_0=L$. The pointed ob
jects of the layers form stable $\\infty$-categories. The tower is analogo
us to the completion tower of a commutative ring with respect to an ideal.
It specializes to Goodwillie's and Weiss' tower.\n\nI am going to tell yo
u a bit about all these towers.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/75/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Clara Aldana (Universidad del Norte)
DTSTART:20221028T150000Z
DTEND:20221028T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/76
DESCRIPTION:Title: Polyakov Formulas for conical singularities in two dimensions.\
nby Clara Aldana (Universidad del Norte) as part of CRM - Séminaire du CI
RGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI
n the first part of the talk I will introduce the regularized determinant
of the Laplace operator on a Riemannian manifold and will explain the cont
ext and the motivation to consider Polyakov's formulas. Then\, I will pres
ent the formula for surfaces with conical singularities and smooth conform
al factors\, and for polygonal domains in a Riemannian surface. I will men
tion how we obtain the so-called variational Polyakov formula for cones an
d sectors and how in these cases we can obtain closed formulas for the det
erminant of the Laplacian. The results presented in this talk are joint wo
rk with Klaus Kirsten and Julie Rowlett\, arxiv.org/abs/2010.02776.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/76/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Manh Tien Nguyen (Oxford University)
DTSTART:20221104T150000Z
DTEND:20221104T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/77
DESCRIPTION:Title: Monotonicity theorems and how to compare them\nby Manh Tien Ngu
yen (Oxford University) as part of CRM - Séminaire du CIRGET / Géométri
e et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI will present two
results. The first one concerns minimal surfaces of the hyperbolic space
and is a relation between their renormalised area (in the sense of Graham
and Witten) and the length of their ideal boundary measured in different m
etrics of the conformal infinity. The second result concerns minimal subma
nifolds of the sphere and is a relation between their volume and antipodal
-ness. Both results were obtained from the same framework\, which involves
new monotonicity theorems and a comparison principle for them.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/77/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Takahiro Aoi (Abuno high school)
DTSTART:20221111T160000Z
DTEND:20221111T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/78
DESCRIPTION:Title: A conical approximation of constant scalar curvature K\\”{a}hler
metrics of Poincar\\’{e} type and log K-semistability\nby Takahiro A
oi (Abuno high school) as part of CRM - Séminaire du CIRGET / Géométrie
et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nGuenancia proved th
at a K\\”{a}hler-Einstein metric of Poincar\\’{e} type is the limit of
a sequence of K\\”{a}hler-Einstein metrics with cone singularities alon
g a smooth divisor. In this talk\, I will explain the recent result which
is an analogue of Guenancia’s result for constant scalar curvature K\\
”{a}hler metrics. In addition\, I will explain that constant scalar curv
ature K\\”{a}hler metrics of Poincar\\’{e} type implies log K-semistab
ility with angle 0.\n\nNote that the talk will take place in Boyer room PK
-5675\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/78/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Viktor Kalvin (Dawson College and Concordia Univ.)
DTSTART:20221118T160000Z
DTEND:20221118T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/79
DESCRIPTION:Title: Determinants of Laplacians on compact surfaces with conical singula
rities\nby Viktor Kalvin (Dawson College and Concordia Univ.) as part
of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held i
n PK-5115.\n\nAbstract\nIn this talk I will discuss new anomaly formulae f
or the zeta regularized spectral determinants of Laplacians on compact Rie
mann surfaces. These formulae are valid for the metrics with conical singu
larities and\, in particular\, show how the determinants of Laplacians dep
end on the orders (angles) of conical singularities. With a simple exampl
e I will show that the extremal properties of the determinants of Laplacia
ns on singular metrics are very different from the classical results of Os
good\, Phillips\, and Sarnak for the smooth metrics. If time permits\, I w
ill also discuss how this is related to Kaehler potentials of metrics on m
oduli spaces\, the famous accessory parameters\, and the celebrated DOZZ f
ormula from the Liouville conformal field theory. The talk is based on a s
eries of recent papers of mine.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/79/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marcin Sroka (CIRGET)
DTSTART:20221125T160000Z
DTEND:20221125T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/80
DESCRIPTION:Title: Monge-Ampere equation in hypercomplex geometry\nby Marcin Sroka
(CIRGET) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie
\n\nLecture held in PK-5115.\n\nAbstract\nI will outline the state of art
concerning the solvability of the so called quaternionic Monge-Ampere equa
tion. This second order\, elliptic\, nonlinear PDE was introduced by Alesk
er and Verbisty as a device for confirming the version of Calabi conjectur
e on hypercomplex manifolds. Its solvability has applications also for obt
aining Calabi-Yau type theorems\nfor some classes of hermitian and hyperhe
rmitian metrics.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/80/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sally Collins (Georgia Tech)
DTSTART:20221209T160000Z
DTEND:20221209T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/81
DESCRIPTION:Title: Homology cobordism and knot concordance\nby Sally Collins (Geor
gia Tech) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie
\n\nLecture held in PK-5115.\n\nAbstract\nThe 0-surgeries of two knots K1
and K2 are homology cobordant rel meridians if there exists an integer hom
ology cobordism X between them such that the two positive knot meridians a
re in the same homology class of X. It is a natural question to ask: if tw
o knots have the “same” 0-surgeries in this sense\, must they be smoot
hly concordant? We give a pair of rationally slice knots as counterexample
\, with one of concordance order two and the other of infinite order\, and
along the way expand upon a Floer homology technique for obstructing tors
ion in the smooth concordance group first introduced by Hom\, Kang\, Park\
, and Stoffregen.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/81/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Paula Truöl (ETH Zurich)
DTSTART:20221216T160000Z
DTEND:20221216T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/82
DESCRIPTION:Title: Strongly quasipositive knots are concordant to infinitely many stro
ngly quasipositive knots\nby Paula Truöl (ETH Zurich) as part of CRM
- Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-51
15.\n\nAbstract\nKnots are smooth embeddings of the (oriented) circle S^1
into the 3-sphere S^3\, usually studied up to an equivalence relation call
ed ambient isotopy. A natural generalization in dimension 4 of the questio
n whether certain knots are isotopic to the trivial knot is the concept of
concordance\, another equivalence relation on the set of knots.\nWe show
that every non-trivial strongly quasipositive knot is (smoothly) concordan
t to infinitely many pairwise non-isotopic strongly quasipositive knots. I
n contrast to our result\, it was conjectured by Baker that concordant str
ongly quasipositive fibered knots are isotopic. Our construction uses a sa
tellite operation whose companion is a slice knot with maximal Thurston-Be
nnequin number -1.\nIn the talk\, we will define the relevant terms necess
ary to understand the theorem in the title\, and explain the context of th
is result. If time permits\, we will say a few words about how the constru
ction extends to links.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/82/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kaya Ferendo (Kaya Ferendo)
DTSTART:20221212T160000Z
DTEND:20221212T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/83
DESCRIPTION:Title: FI-calculus and representation stability\nby Kaya Ferendo (Kaya
Ferendo) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie
\n\nLecture held in PK-5115.\n\nAbstract\nFI is the category of finite set
s and injections. Representation stability is an appealing phenomenon enjo
yed by certain functors from FI to\, for example\, rational vector spaces.
The rational cohomology of certain families of moduli spaces is a key exa
mple. Functor calculus is a family of techniques and structures that are u
seful in the study of functors between certain infinity-categories. In thi
s talk\, we'll see that representation stability emerges as a facet of a n
ew kind of functor calculus and discuss some of the features of this funct
or calculus.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/83/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shih-Kai Chiu (Oxford University)
DTSTART:20230127T160000Z
DTEND:20230127T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/84
DESCRIPTION:Title: Calabi-Yau manifolds with maximal volume growth\nby Shih-Kai Ch
iu (Oxford University) as part of CRM - Séminaire du CIRGET / Géométrie
et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nCalabi-Yau manifold
s with maximal volume growth are complete Ricci-flat Kähler manifolds whe
re any r-ball has volume at least r^m up to a uniform constant factor and
m is the real dimension of the manifold. Bishop-Gromov volume comparison t
heorem implies that such growth is indeed maximal. This notion generalizes
the more well-known notion of asymptotically conical (AC) manifolds. Cont
rary to the AC case\, the asymptotic cones at infinity in general can have
\nnon-isolated singularities. In this talk\, I will give a (biased) survey
of the recent progress on this ongoing topic.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/84/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yueqiao Wu (Michigan Univ)
DTSTART:20230120T160000Z
DTEND:20230120T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/85
DESCRIPTION:Title: A non-Archimedean characterization of local K-stability\nby Yue
qiao Wu (Michigan Univ) as part of CRM - Séminaire du CIRGET / Géométri
e et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nLog Fano cone sing
ularities are generalizations of cones over Fano varieties\, and have a lo
cal K-stability theory extending the one for Fano varieties. In this talk\
, we aim to give a characterization for local K-stability from a non-Archi
medean point of view. As a consequence of this characterization\, we can s
how that a log Fano cone singularity is K-polystable with respect to a lar
ger class of test configurations if it admits a Ricci-flat Kähler cone me
tric\, strengthening earlier results of Collins-Székelyhidi and Li.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/85/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicholas McCleerey (Michigan Univ)
DTSTART:20230203T160000Z
DTEND:20230203T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/86
DESCRIPTION:by Nicholas McCleerey (Michigan Univ) as part of CRM - Sémina
ire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\nAbst
ract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/86/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tristan Ozuch (MIT)
DTSTART:20230324T150000Z
DTEND:20230324T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/88
DESCRIPTION:Title: 4-dimensional specific aspects of Ricci flows\nby Tristan Ozuch
(MIT) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\
nLecture held in PK-5115.\n\nAbstract\nRicci flow has been extensively stu
died\, and most results are either true only in dimension 3 or hold in eve
ry dimension. However\, given the potential topological applications\, a t
heory specific to the 4-dimensional situation is desirable. In this discus
sion\, I will present tools and techniques that are unique to the 4-dimens
ional case.\n\nTogether with A. Deruelle\, we introduce a notion of stabil
ity for orbifold singularities. This notion helps to explain the formation
of orbifold singularities along Ricci flow. Moreover\, in collaboration w
ith K. Naff\, we utilize self-duality in dimension 4 to simplify the evolu
tion equations of curvature. This approach lets us uncover intriguing conn
ections between Ricci flow and Yang-Mills flow.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/88/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nathan Grieve (Carleton University)
DTSTART:20230224T160000Z
DTEND:20230224T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/89
DESCRIPTION:Title: On Harder-Narasimhan data and the Central Limit Theorem\nby Nat
han Grieve (Carleton University) as part of CRM - Séminaire du CIRGET / G
éométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nStarting
with the work of Harder and Narasimhan\, the concept of canonical (Harder
and Narasimhan) filtration emerged as a fundamental tool for measuring the
extent to which a given object in a suitable category fails to be slope s
emistable. In this lecture\, I will discuss an abstract concept of Harder
and Narasimhan data which I formulated as a tool for expanding on the key
technical techniques of Codogni and Patakfalvi\, which arise in their wor
k on weak positivity of the CM line bundle over the moduli stack of K-semi
stable Fano varieties. Another source of motivation is Grayson's lattice
reduction theory via slope semistability. Finally\, via theory of Falting
s and Wustholz\, for slope semistabilty of filtered vector spaces\, there
is a strong overlap with techniques from Diophantine approximation for lin
ear series. As application of this circle of ideas\, I will explain a rec
ent result which gives a filtered vector space analogue to the above menti
oned key technical result of Codogni and Patakfalvi.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/89/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maxence Mayrand (Sherbrooke University)
DTSTART:20230310T160000Z
DTEND:20230310T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/90
DESCRIPTION:Title: Hyperkähler metrics via deformation theory\nby Maxence Mayrand
(Sherbrooke University) as part of CRM - Séminaire du CIRGET / Géométr
ie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nHyperkähler stru
ctures are special holonomy metrics with a particularly rich geometry. I w
ill discuss methods for constructing such metrics\, and the weaker notion
of hypercomplex structures\, using the theory of deformation of complex st
ructures. As a consequence\, we obtain new hyperkähler metrics on certain
Lie groupoids\, namely\, integrations of holomorphic Poisson surfaces\, b
y using results on the deformation theory of such surfaces.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/90/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emily Cliff (Sherbrooke University)
DTSTART:20230421T140000Z
DTEND:20230421T150000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/91
DESCRIPTION:Title: Smooth 2-groups and their principal bundles\nby Emily Cliff (Sh
erbrooke University) as part of CRM - Séminaire du CIRGET / Géométrie e
t Topologie\n\nLecture held in PK-5115.\n\nAbstract\nA 2-group is a catego
rical generalization of a group: it's a category with a multiplication ope
ration which satisfies the usual group axioms only up to coherent isomorph
isms. In this talk I will introduce the category of Lie groupoids and bibu
ndles between them\, in order to provide the definition of a smooth 2-grou
p. I will define principal bundles for such a smooth 2-group\, and provide
classification results that allow us to compare them to principal bundles
for ordinary groups. As a consequence in specific settings\, we obtain a
categorification of the Freed--Quinn line bundle over the moduli stack Bun
_G(X) for a finite group G and Riemann surface X. This is a line bundle wh
ich plays an important role in Dijkgraaf--Witten theory (i.e. Chern--Simo
ns theory for the finite group G). This talk is based on joint work with D
an Berwick-Evans\, Laura Murray\, Apurva Nakade\, and Emma Phillips. I wil
l not assume any previous background on 2-groups\, Lie groupoids\, or Dijk
graaf--Witten theory.\n\nNote that we have 2 talks this week\, one at 10 a
m (E. Cliff)\, another one at 11 am (A. Adem).\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/91/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maxime Fortier Bourque (Université de Montréal)
DTSTART:20230217T160000Z
DTEND:20230217T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/92
DESCRIPTION:Title: The systole of hyperbolic surfaces\nby Maxime Fortier Bourque (
Université de Montréal) as part of CRM - Séminaire du CIRGET / Géomét
rie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nThe systole of a
Riemannian manifold is defined as the infimal length of its closed geodes
ics that are not contractible and was studied by Berger and Gromov in the
70's and 80's. In this talk\, I will survey recent results on the systole
of closed hyperbolic surfaces. In particular\, I will explain how to const
ruct a surface out of polygons glued along a graph in a way that we can de
termine its systole. Variants of this construction yield numerous local ma
xima for the systole\, critical points of lower index than expected\, and
are used to prove that the dimension of a certain set defined by Thurston
is larger than hoped.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/92/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Panagiotis Dimakis (Stanford University)
DTSTART:20230317T150000Z
DTEND:20230317T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/93
DESCRIPTION:Title: BAA branes on the Hitchin moduli space from solutions to the extend
ed Bogomolny equations\nby Panagiotis Dimakis (Stanford University) as
part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture
held in PK-5115.\n\nAbstract\nBAA branes are complex Lagrangian submanifol
ds of the Hitchin space. Recently\, there has been interest in these objec
ts due to their appearance in mirror symmetry conjectures and due to their
intimate connection with the geometry of the Hitchin space. In this talk
I will introduce the above notions. Then I will introduce the extended Bog
omolny equations and explain how their solutions lead to holomorphic data
associated with a Riemann surface. As long as the degree of a naturally oc
curing line bundle is not too negative\, I will show that the moduli of th
ese holomorphic data is a BAA brane. Some of the BAA branes obtained this
way are known but some are new.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/93/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mihai Paun (Universitat Bayreuth)
DTSTART:20230331T150000Z
DTEND:20230331T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/94
DESCRIPTION:Title: Infinitesimal extension of pluricanonical forms and injectivity.\nby Mihai Paun (Universitat Bayreuth) as part of CRM - Séminaire du CIR
GET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nWe
will present some of the main results obtained in collaboration with J. C
ao in the preprint arXiv:2012.05063.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/94/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Fraser Binns (Boston College)
DTSTART:20230414T150000Z
DTEND:20230414T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/95
DESCRIPTION:Title: Almost L-space knots\nby Fraser Binns (Boston College) as part
of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held i
n PK-5115.\n\nAbstract\nHeegaard Floer homology is a powerful package of i
nvariants in low dimensional topology due originally to Ozsváth-Szabó. A
n L-space knot is a knot admitting surgeries to a manifold with Heegaard F
loer homology of minimal rank. Ozsváth-Szabó classified the knot Floer h
omology of L-space knots from which it follows that L-space knots satisfy
various strong topological conditions. I will discuss a generalization of
Ozsváth-Szabó's result to "almost L-space knots"\; i.e. knots which admi
t surgeries to manifolds with Heegaard Floer homology of next to minimal r
ank.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/95/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alejandro Adem (University of British Columbia)
DTSTART:20230421T150000Z
DTEND:20230421T160000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/96
DESCRIPTION:Title: Minimal Euler Characteristics for Even-Dimensional Manifolds with F
inite Fundamental Group\nby Alejandro Adem (University of British Colu
mbia) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n
Lecture held in PK-5115.\n\nAbstract\nIn this talk we will discuss estimat
es for the minimal Euler characteristic of even dimensional manifolds with
a given finite fundamental group and a highly connected universal cover.
In particular we strengthen the Hausmann-Weinberger invariants and extend
them to higher dimensions. As an application we obtain new restrictions fo
r non-abelian finite groups arising as fundamental groups of rational homo
logy 4–spheres. This is joint work with Ian Hambleton.\n\nNote that we h
ave 2 talks this week\, one at 10 am (E. Cliff)\, another one at 11 am (A.
Adem).\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/96/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xiaojun Wu (Universität Bayreuth)
DTSTART:20230428T150000Z
DTEND:20230428T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/97
DESCRIPTION:Title: Compact K\\"ahler threefold with nef anticanonical line bundle\
nby Xiaojun Wu (Universität Bayreuth) as part of CRM - Séminaire du CIRG
ET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nIn
my talk\, I will discuss a recent collaboration with Shin-ichi Matsumura o
n compact Kähler threefolds with nef anticanonical line bundles. Thanks t
o the breakthrough result of Cao-Höring\, we can focus on the non-project
ive case. Using the Kähler threefold MMP developed by Höring-Peternell\,
we have shown that there are only three possibilities for such manifolds:
(1) Calabi-Yau manifolds\; (2) projectivizations of numerical flat vector
bundles over a torus\; (3) products of K3 surfaces with projective lines.
I will begin by reviewing the arguments of Cao-Höring and then explain t
he different ingredients we used to establish our results in the Kähler s
etting.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/97/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simon Jubert (UQAM & Université de Toulouse)
DTSTART:20230512T150000Z
DTEND:20230512T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/98
DESCRIPTION:Title: A Yau-Tian-Donaldson correspondence on a class of toric fibrations<
/a>\nby Simon Jubert (UQAM & Université de Toulouse) as part of CRM - Sé
minaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n
\nAbstract\nThe Yau--Tian--Donaldson conjecture predicts that the existenc
e of an\nextremal metric (in the sense of Calabi) in a given Kähler class
of\nKähler manifold is equivalent to a certain algebro-geometric notion
of\nstability of this class. In this talk\, we will discuss a resolution o
f\nthis conjecture for a certain type of toric fibrations\, called\nsemisi
mple principal toric fibrations. One of the main assets of these\nfibratio
ns is that they come equipped with a connection which allows\ndefining\, f
rom any Kähler metrics on the toric fiber X\, a Kähler\nmetric on the to
tal space Y. After an introduction to the Calabi\nProblem for general comp
act Kähler manifolds\, we will focus on the\nweighted toric setting. Then
\, I will explain how to translate the\nCalabi problem on Y\, to a weighte
d cscK problem on the corresponding\ntoric fiber X (arxiv paper: arXiv:21
08.12297).\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/98/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yoshinori Hashimoto (Osaka Metropolitan Univ)
DTSTART:20230505T150000Z
DTEND:20230505T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/99
DESCRIPTION:Title: Uniform Hörmander estimates for flat nontrivial line bundles\n
by Yoshinori Hashimoto (Osaka Metropolitan Univ) as part of CRM - Séminai
re du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbs
tract\nHörmander’s $L^2$-estimates for the $\\bar{\\partial}$ operators
on holomorphic line bundles are of fundamental importance in complex anal
ytic geometry\, whose conventional proof crucially relies on the positivit
y of the line bundle. In this talk\, we prove the $L^2$-estimates for the
solutions to the $\\bar{\\partial}$ equation that hold uniformly for all f
lat nontrivial line bundles on compact Kähler manifolds\, whose main feat
ure is the quantitative description of the blow-up behaviour as the line b
undle approaches the trivial one. A key ingredient in the proof is the obs
ervation that line bundles with vanishing first Chern classes are topologi
cally trivial and can be identified with the trivial bundle with the "pert
urbed" $\\bar{\\partial}$ operator which we define in terms of coordinates
on the Picard variety. This is a joint work with Takayuki Koike.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/99/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Litt (University of Toronto)
DTSTART:20230915T150000Z
DTEND:20230915T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/100
DESCRIPTION:Title: Hodge theory\, braid groups\, and some questions about 2x2 matrice
s\nby Daniel Litt (University of Toronto) as part of CRM - Séminaire
du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstra
ct\nLet $X_n$ be the set of conjugacy classes of n-tuples of 2x2 matrices
whose product is the identity matrix--equivalently\, the character variety
of a n-punctured sphere. There is a natural braid group action on $X_n$\,
whose study goes back to work of Markoff in the late 19th century. The mo
st basic question one can ask about this action\, which dates to work of P
ainlevé\, Fuchs\, Schlesinger\, and Garnier in the beginning of the 20th
century\, is: what are the finite orbits? I'll explain the history of this
question\, as well as some recent work\, joint with Lam and Landesman\, i
n which we give a complete classification of such finite orbits\, by algeb
ro-geometric methods\, when at least one of the matrices in question has i
nfinite order.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/100/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Masafumi Hattori (Kyoto University)
DTSTART:20230922T150000Z
DTEND:20230922T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/101
DESCRIPTION:Title: K-stability of CY fibrations over curves\nby Masafumi Hattori
(Kyoto University) as part of CRM - Séminaire du CIRGET / Géométrie et
Topologie\n\nLecture held in PK-5115.\n\nAbstract\nIn K-stability\, the ch
aracterization of K-stable varieties is well-studied when $K_X$ is ample o
r X is a Calabi-Yau or Fano variety. However\, K-stability of Fano fibrati
ons or Calabi-Yau fibrations (i.e.\, $K_X$ is relatively trivial) is not k
nown much in algebraic geometry. On the other hand\, cscK problems on fibr
ations are studied by Fine\, Jian-Shi-Song and Dervan-Sektnan in Kahler ge
ometry. We introduce adiabatic K-stability (If $f:(X\,H)\\to (B\,L)$ is a
fibration of polarized varieties\, this means that K-stability of $(X\,aH+
L)$ for sufficiently small a) and show that adiabatic K-semistability of C
alabi-Yau fibration implies log-twisted K-semistability of the base variet
y by applying the canonical bundle formula and the result on J-stability.
If the base is a curve\, we also obtain a partial converse. In this talk\,
I would like to explain our main results.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/101/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tian-Jun Li (University of Minnesota)
DTSTART:20230928T173000Z
DTEND:20230928T183000Z
DTSTAMP:20260404T024900Z
UID:CIRGET/102
DESCRIPTION:Title: Uniruled symplectic surfaces\nby Tian-Jun Li (University of Mi
nnesota) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\
n\nLecture held in PK-5675.\n\nAbstract\nWe survey several aspects of the
geometry of uniruled symplectic surfaces.\n\nRoom PK-5675\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/102/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Claude LeBrun (Stony Brook)
DTSTART:20231006T150000Z
DTEND:20231006T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/103
DESCRIPTION:Title: Gravitational Instantons\, Weyl Curvature\, and Conformally Kahler
Geometry\nby Claude LeBrun (Stony Brook) as part of CRM - Séminaire
du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstra
ct\nThis talk will describe my recent joint work with Olivier Biquard and
Paul Gauduchon on ALF Ricci-flat Riemannian 4-manifolds that are not hyper
-Kahler. Our main result largely characterizes the known solutions in term
s of an open\, purely Riemannian curvature condition.\n\nWe will have two
seminars on the 6th of October ! \n11 am : Claude Lebrun\n 2 pm : Simone
Gutt\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/103/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simone Gutt (Université Libre de Bruxelles)
DTSTART:20231006T180000Z
DTEND:20231006T191500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/104
DESCRIPTION:Title: Around almost complex structures\nby Simone Gutt (Université
Libre de Bruxelles) as part of CRM - Séminaire du CIRGET / Géométrie et
Topologie\n\nLecture held in PK-5115.\n\nAbstract\nSmooth almost complex
structures on manifolds (in particular on symplectic manifolds) have vario
us integrability properties.\nWe have been interested in defining relevan
t properties which a non integrable almost complex structure may have\, in
terms of its Nijenhuis tensor.\nIn particular\, we define the notions of
minimally or maximally non integrable almost complex structures\, and the
notion of transverse complex structure defined by an almost complex struct
ure.\nWe review some Dolbeault-type cohomologies associated to an almost c
omplex structure.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/104/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thomas Barthelmé (Queen's University)
DTSTART:20231013T150000Z
DTEND:20231013T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/105
DESCRIPTION:Title: Group actions on bifoliated planes and classification of (pseudo)-
Anosov flows in dimension 3\nby Thomas Barthelmé (Queen's University)
as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLectu
re held in PK-5115.\n\nAbstract\nAn old problem in dynamical systems is to
try to classify Anosov flows up to orbit-equivalence. This question is pa
rticularly interesting in dimension 3 where we both have lots of examples
and a rich\, but still poorly understood\, relationships between the dynam
ics of the flow and the topology of the manifold. By a result of T. Barbot
\, classifying Anosov flows (or more general pseudo-Anosov flows) in dimen
sion 3 up to orbit equivalence restricts to classifying\, up to conjugacy\
, certain actions of \\pi_1(M) on the orbit space\, a topological plane wi
th two transverse foliations. \n\nIn this talk\, I will recall the above
and discuss a new complete invariant for transitive (pseudo)-Anosov flows
which often reduces to just knowing which conjugacy classes in \\pi_1(M) a
re represented by periodic orbits of the flow. \n\nIf time permits\, I’l
l talk about some applications with link to contact geometry. This is all
joint work with Kathryn Mann\, Steven Frankel and Sergio Fenley.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/105/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Abdellah Lahdili (UQAM)
DTSTART:20231020T150000Z
DTEND:20231020T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/106
DESCRIPTION:Title: The Einstein-Hilbert functional in Kähler and Sasaki geometry
\nby Abdellah Lahdili (UQAM) as part of CRM - Séminaire du CIRGET / Géom
étrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nGiven a polar
ised K\\"ahler manifold $(M\,L)$\, we consider the circle bundle associate
d to the polarization with the induced transversal holomorphic structure.
The space of contact structures compatible with this transversal structure
is naturally identified with a bundle\, of infinite rank\, over the space
of K\\"ahler metrics in the first Chern class of $L$. We show that the Ei
nstein--Hilbert functional of the associated Tanaka--Webster connections i
s a functional on this bundle\, whose critical points are constant scalar
curvature Sasaki structures. In particular\, when the group of automorphis
ms of $(M\,L)$ is discrete\, these critical points correspond to constant
scalar curvature K\\"ahler metrics in the first Chern class of $L$. We sho
w that the Einstein--Hilbert functional satisfies some monotonicity proper
ties along some one-parameter families of CR-contact structures that are n
aturally associated to test configurations\, and that its limit on the cen
tral fiber of a test configuration is related to the Donaldson--Futaki inv
ariant. As a by-product\, we show that the existence of cscK metrics on a
polarized manifold implies K-semistability. This is a joint work with Evel
ine Legendre and Carlo Scarpa.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/106/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yann Rollin (Université de Nantes)
DTSTART:20231027T150000Z
DTEND:20231027T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/107
DESCRIPTION:Title: Moment maps in Symplectic geometry and applications to PL symplect
ic geometry\nby Yann Rollin (Université de Nantes) as part of CRM - S
éminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.
\n\nAbstract\nClassical results of symplectic geometry\, like Darboux theo
rem\, are open problems in piecewise linear symplectic geometry. This is n
otoriously due to the fact that diffeomorphisms flow techniques fail in th
is context.\n\nI will discuss certain moment map geometries of interest\,
with applications to piecewise linear symplectic geometry. In particular t
he space of symplectic diffeomorphisms of the torus T^4 can be interpreted
as the vanishing locus of a certain hyperKähler moment maps. An interest
ing moment map flow can be deduced as a key tool to compare homotopy prope
rties of the groups of diffeomorphisms and symplectomorphisms of the torus
T^4.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/107/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eva Miranda (Universitat Politècnica de Catalunya)
DTSTART:20231103T150000Z
DTEND:20231103T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/108
DESCRIPTION:Title: The Weinstein conjecture\, 44 years later\nby Eva Miranda (Uni
versitat Politècnica de Catalunya) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nThe W
einstein conjecture (1979) concerns the existence of periodic orbits of Re
eb vector fields. Over the years\, the conjecture has undergone significan
t developments. In this talk\, I will provide a historical overview of the
Weinstein conjecture and discuss variations for singular contact manifold
s. I will relate the singular Weinstein conjecture with the existence of
escape orbits in celestial mechanics and fluid dynamics. Time permitting\,
I will conclude with a counterexample to the singular Weinstein conjectur
e.\n\nThis talk is based on joint works with Josep Fontana-McNally\, Cédr
ic Oms\, and Daniel Peralta-Salas (some of them ongoing).\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/108/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mike Wong (University of Ottawa)
DTSTART:20231110T160000Z
DTEND:20231110T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/109
DESCRIPTION:by Mike Wong (University of Ottawa) as part of CRM - Séminair
e du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstra
ct: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/109/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Joe Boninger (Boston College)
DTSTART:20231117T160000Z
DTEND:20231117T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/110
DESCRIPTION:by Joe Boninger (Boston College) as part of CRM - Séminaire d
u CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstract:
TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/110/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Benoit Charbonneau (Waterloo Univ.)
DTSTART:20240112T160000Z
DTEND:20240112T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/111
DESCRIPTION:Title: Instantons symétriques\nby Benoit Charbonneau (Waterloo Univ.
) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLect
ure held in PK-5115.\n\nAbstract\nSpencer Whitehead et moi avons développ
é une approche systématique pour étudier les instantons sur R4 qui sont
invariants sous l’action de groupes d’isométries de polyèdres. Dans
cet exposé\, je décrirai cette approche et quelques résultats obtenus
en l’utilisant.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/111/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jarl G. Taxeras Flaten (Western Univ. Canada)
DTSTART:20240119T160000Z
DTEND:20240119T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/112
DESCRIPTION:Title: Central types and their bands\nby Jarl G. Taxeras Flaten (West
ern Univ. Canada) as part of CRM - Séminaire du CIRGET / Géométrie et T
opologie\n\nLecture held in PK-5115.\n\nAbstract\nWe will introduce and mo
tivate the concept of a central type (or space) and explain their associat
ed notion of torsor\, called a band. Much like one can deloop a group G by
its type of torsors BG\, the type of bands of a central type A forms a de
looping of A. Moreover\, we show that the delooping of A is itself central
\, allowing us to iterate. This procedure yields a new construction of Eil
enberg-Mac Lane spaces\, which are examples of central types. We also prod
uce a mysterious formula for delooping pointed self-maps of A\, and study
the moduli space of H-space structures on a pointed type.\n\nOur results h
ave been shown in homotopy type theory\, and most have been formalized usi
ng the Coq-HoTT library [1]. For this talk\, we do not assume familiarity
with type theory\; rather\, we will translate our results for topologists.
This work is joint with Ulrik Buchholtz\, Dan Christensen\, and Egbert Ri
jke. [2]\n\n[1] https://github.com/jarlg/central-types\n[2] https://arxiv.
org/abs/2301.02636\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/112/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ethan Ross (Toronto Univ.)
DTSTART:20240126T160000Z
DTEND:20240126T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/113
DESCRIPTION:Title: Reduction of Polarizations\nby Ethan Ross (Toronto Univ.) as p
art of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture he
ld in PK-5115.\n\nAbstract\nA polarization on a symplectic manifold $(M\,\
\omega)$ is an involutive complex Lagrangian subbundle $P$ of the complexi
fied tangent bundle $T^\\mathbb{C} M$. Kähler structures are special case
s of polarizations which intersect their complex conjugates trivially. Muc
h work has been done discussing how Kähler structures behave under symple
ctic reduction\, with only partial results for the reduction of more gener
al polarizations. In this talk\, I will discuss the reduction of polarizat
ions and also extend to the setting of singular reduction explored by Sjam
aar-Lerman.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/113/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chi Cheuk Tsang (UQAM)
DTSTART:20240202T160000Z
DTEND:20240202T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/114
DESCRIPTION:Title: Motivations and progress on the Fried-Ghys conjecture\nby Chi
Cheuk Tsang (UQAM) as part of CRM - Séminaire du CIRGET / Géométrie et
Topologie\n\nLecture held in PK-5115.\n\nAbstract\nThe Fried-Ghys conjectu
re states that any two transitive Anosov flows with orientable stable and
unstable foliations are almost equivalent\, i.e. they are the same up to h
omeomorphism and reparametrization after drilling out finitely many closed
orbits. In this talk\, we will discuss some motivations underlying this c
onjecture and some known partial results.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/114/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Charles Cifarelli (UQAM)
DTSTART:20240209T160000Z
DTEND:20240209T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/115
DESCRIPTION:Title: Steady gradient Kähler-Ricci solitons and Calabi-Yau metrics on C
^n\nby Charles Cifarelli (UQAM) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI will
present recent joint work with V. Apostolov on a new construction of comp
lete steady gradient Kähler-Ricci solitons on C^n\, using the theory of h
amiltonian 2 forms\, introduced by Apostolov-Calderbank-Gauduchon-Tønnese
n-Friedman\, as an Ansatz. The metrics come in families of two types with
distinct geometric behavior\, which we call Cao type and Taub-NUT type. In
particular\, the Cao type and Taub-NUT type families have a volume growth
rate of r^n and r^{2n-1}\, respectively. Moreover\, each Taub-NUT type fa
mily contains a codimension 1 subfamily of complete Ricci-flat metrics.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/115/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vamsi Pritham Pingali (Indian Institute of Science)
DTSTART:20240315T150000Z
DTEND:20240315T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/116
DESCRIPTION:Title: Ampleness of vector bundles and canonical metrics\nby Vamsi Pr
itham Pingali (Indian Institute of Science) as part of CRM - Séminaire du
CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract
\nHartshorne ampleness of vector bundles will be introduced and a generali
sation of a criterion (due to Schneider and Tancredi) to recognise ample b
undles will be presented. This work is joint with Indranil Biswas. We shal
l also introduce differentio-geometric positivity conditions and discuss P
DE that are relevant for studying the Griffiths conjecture that asserts th
at Hartshorne ample bundles admit Griffiths positively curved metrics.\n\n
By zoom.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/116/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bin Guo (Rutgers University)
DTSTART:20240322T150000Z
DTEND:20240322T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/117
DESCRIPTION:Title: Geometric estimates in Kahler geometry\nby Bin Guo (Rutgers Un
iversity) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie
\n\nLecture held in PK-5115.\n\nAbstract\nWe will discuss the role of comp
lex Monge-Ampere equations as auxiliary equations in deriving sharp analyt
ic and geometric estimates in Kahler geometry. By studying Green's functio
ns\, we will explore how to derive estimates for diameters and establish u
niform Sobolev inequalities on Kähler manifolds\, which depend only on en
tropy of the volume form and are independent of the lower bound of the Ric
ci curvature. This talk is based on joint works with D. H. Phong\, J. Son
g\, and J. Sturm.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/117/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Federico Salmoiraghi (Queens Univ.)
DTSTART:20240405T150000Z
DTEND:20240405T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/118
DESCRIPTION:Title: Foliations\, contact structures and Anosov flows in dimension 3\nby Federico Salmoiraghi (Queens Univ.) as part of CRM - Séminaire du C
IRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\n
Anosov flows are an important class of dynamical systems due to their ergo
dic and geometric properties. Even though they represent examples of chaot
ic dynamics\, they enjoy the remarkable property of being stable under sma
ll perturbations. In this talk\, I will explain how\, perhaps surprisingly
\, Anosov flows are related to both integrable plane fields (foliations) a
nd totally non-integrable plane fields (contact structures). The latter re
presents a less-studied approach that has the potential to make new connec
tions to other branches of mathematics\, such as symplectic geometry and H
amiltonian dynamics. Along the way\, I will discuss some applications and
examples with particular emphasis on the theory of surgery of Anosov flows
.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/118/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xuemiao Chen (Western Univ. Canada)
DTSTART:20240412T150000Z
DTEND:20240412T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/119
DESCRIPTION:Title: On Vafa-Witten equations over Kaehler manifolds\nby Xuemiao Ch
en (Western Univ. Canada) as part of CRM - Séminaire du CIRGET / Géomét
rie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI will talk abou
t some analytic properties of solutions to the Vafa-Witten equations over
compact Kaehler manifolds. Simple obstructions to the existence of nontriv
ial solutions are identified. The gauge theoretical compactness for the C^
* invariant locus of the moduli space behaves similarly as the Hermitian-Y
ang-Mills connections. More generally\, this holds for solutions with unif
ormly bounded spectral covers such as nilpotent solutions. When spectral c
overs are unbounded\, we manage to take limits of the renormalized Higgs f
ields which are intrinsically characterized by the convergence of the asso
ciated spectral covers. This gives a simpler proof for Taubes’ results o
n rank two solutions over Kaehler surfaces together with a new complex geo
metric interpretation.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/119/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andras Stipsicz (Renyi institute)
DTSTART:20240419T150000Z
DTEND:20240419T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/120
DESCRIPTION:by Andras Stipsicz (Renyi institute) as part of CRM - Séminai
re du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstr
act: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/120/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Frédéric Rochon (UQAM)
DTSTART:20240913T150000Z
DTEND:20240913T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/121
DESCRIPTION:Title: Warped quasi-asymptotically conical Calabi-Yau metrics\nby Fr
édéric Rochon (UQAM) as part of CRM - Séminaire du CIRGET / Géométrie
et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nWe will explain how
to construct new examples of complete Calabi-Yau manifolds of maximal vol
ume growth on certain smoothings of Cartesian products of Calabi-Yau cones
. A description of the geometry at infinity will be given in terms of a c
ompactification by a manifold with corners obtained through a suitable seq
uence of blow-ups. A key analytical step in the construction of these Cal
abi-Yau metrics is to derive good mapping properties of the Laplacian on s
ome suitable weighted Hölder spaces. Our methods also produce Calabi-Ya
u metrics with an isolated conical singularity modelled on a Calabi-Yau co
ne distinct from the tangent cone at infinity\, in particular yielding a t
ransition behavior between different Calabi-Yau cones as conjectured by Ya
ng Li. This is used to exhibit many examples where the tangent cone at in
finity does not uniquely specify a Calabi-Yau metric with exact Kähler fo
rm. This is a joint work with Ronan Conlon.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/121/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nathaniel Sagman (University of Luxembourg)
DTSTART:20240927T150000Z
DTEND:20240927T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/122
DESCRIPTION:Title: Labourie's conjecture and Higgs bundles at high energy\nby Nat
haniel Sagman (University of Luxembourg) as part of CRM - Séminaire du CI
RGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nF
or S a closed surface of genus at least 2\, Hitchin representations from p
i_1(S) to PSL(n\,R) naturally generalize Fuchsian representations to PSL(2
\,R). Labourie proved that every Hitchin representation comes with an inva
riant minimal surface in the corresponding symmetric space. Motivated by t
he mapping class group action and potential Kahler metrics on the space of
Hitchin representations\, he conjectured that uniqueness holds as well. \
n\nIn this talk we'll explain how we used Higgs bundles to produce large a
rea minimal surfaces that give counterexamples to Labourie's conjecture\,
and we'll overview related advances in the theory of Higgs bundles at high
energy. This is all joint with Peter Smillie.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/122/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Julien Paupert (Arizona State)
DTSTART:20241004T150000Z
DTEND:20241004T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/123
DESCRIPTION:Title: Complex hyperbolic and projective deformations of Kleinian groups<
/a>\nby Julien Paupert (Arizona State) as part of CRM - Séminaire du CIRG
ET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nWe
consider deformations of discrete subgroups (in particular lattices) of SO
(3\,1) into the larger Lie groups SU(3\,1) and SL(4\,R). In particular\, w
hen such deformations exist we would like to know whether or not they rema
in discrete and faithful in some neighborhood of the inclusion. We will re
view results of Cooper-Long-Thistlethwaite and Ballas-Danciger-Lee in the
manifold case\, then discuss recent joint work with Morwen Thistlethwaite
for certain Bianchi groups.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/123/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Kottke (New College of Florida)
DTSTART:20241018T150000Z
DTEND:20241018T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/124
DESCRIPTION:Title: Geometric analysis on quasi-fibered boundary (QFB) manifolds\n
by Chris Kottke (New College of Florida) as part of CRM - Séminaire du CI
RGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nT
he known complete non-compact hyperkahler manifolds include several famili
es of moduli spaces\, including the moduli spaces of SU(2) monopoles on R^
3 and the Hilbert schemes of points on C^2\, among others. Beyond dimensio
n 4\, the asymptotic geometries of these spaces are not uniform\, but exhi
bit singularities `at infinity’\, presenting a challenge for geometric a
nalysis. I will report on a framework for geometric analysis for a broad c
lass of `quasi-fibered boundary’ (QFB) metrics. The point of view is to
consider compactifications of these spaces as manifolds with corners\, whi
ch can also be thought of as resolutions of certain stratified spaces. Thr
ough a pseudodifferential parametrix construction for the Hodge de Rham op
erator and an analysis relating weighted L2 cohomology with intersection c
ohomology\, we prove a new case of Sen’s conjecture for the L2 cohomolog
y of the charge 3 monopole moduli space\, and of the Vafa-Witten conjectur
e for the L2 cohomology of Hilbert schemes in all cases. This is joint wor
k with F. Rochon\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/124/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Freid Tong (University of Toronto)
DTSTART:20241025T150000Z
DTEND:20241025T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/125
DESCRIPTION:Title: Complete Calabi-Yau metrics and optimal transport problems\nby
Freid Tong (University of Toronto) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nCalabi
-Yau metrics are Ricci-flat and K\\"ahler metrics and they are a central p
art of K\\"ahler geometry. The construction of Calabi-Yau metrics on compa
ct K\\"ahler manifolds has been understood since Yau's resolution of the C
alabi conjecture. By contrast\, the situation in the complete non-compact
case is much more intricate and remains an active area of research. In thi
s talk\, I will discuss some recent developments in the study of complete
Calabi-Yau metrics where the regularity theory of an optimal transport pro
blem plays a big role. This is based on joint work with Tristan Collins an
d Shing-Tung Yau.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/125/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bruno de Oliveira (Miami Univ)
DTSTART:20241108T160000Z
DTEND:20241108T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/127
DESCRIPTION:Title: Chern numbers ratios of surfaces with big cotangent bundle\nby
Bruno de Oliveira (Miami Univ) as part of CRM - Séminaire du CIRGET / G
éométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nBigness o
f the cotangent bundle of a projective manifold is the condition that the
growth of the space of sections of the symmetric powers of the cotangent b
undle is maximal. The condition implies that the manifold is of general ty
pe\, that is\, its canonical bundle $K_X$ satisfies the same condition. If
an algebraic surface $X$ has a big cotangent bundle\, then $X$ satisfies
Green-Griffiths-Lang conjecture. This talk examines the implication of our
CMS-criterion for bigness of the cotangent bundle\, a condition about n
umerical invariants of $X$\, towards the possible ratios of the Chern numb
ers $c_1^2=K_X^2$ and $c_2=\\xi_{top}(X)$ of surfaces $X$ with big cotange
nt bundle. We present several conjectures concerning these ratios motiva
ted by the CMS-criterion and examples supporting the conjectures.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/127/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kathryn Mann (Cornell University)
DTSTART:20241122T160000Z
DTEND:20241122T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/128
DESCRIPTION:Title: (bi)-Foliations of the plane and laminations of the circle\nby
Kathryn Mann (Cornell University) as part of CRM - Séminaire du CIRGET /
Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nA "bifo
liation" of a two-dimensional space is a way of covering it with local cha
rts to the Euclidean plane R^2 so that overlap maps in R^2 match up the ve
rtical and horizontal coordinate directions. Such objects arise naturally
in many dynamical contexts such as Anosov diffeomorphisms on surfaces\, o
r flows on 3-manifolds.\nA trick due to Mather lets one compactify a bifol
iated plane with a "circle at infinity" using the data of the bifoliation.
In recent work with Barthelmé and Bonatti\, we studied the inverse ques
tion: what is the minimum amount of data from infinity that allows one to
reverse this procedure and uniquely reconstruct a bifoliation of the plane
? This talk will explain the answer! While our motivation for this ques
tion was the problem of classifying pseudo-Anosov flows\, the problem and
solution are entirely in the realm of low-dimensional topology.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/128/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Olivier Martin (IMPA)
DTSTART:20241213T160000Z
DTEND:20241213T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/129
DESCRIPTION:Title: Isotrivial Lagrangian fibrations of hyper-Kähler manifolds of K3^
[n] and Kum_n type\nby Olivier Martin (IMPA) as part of CRM - Séminai
re du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbs
tract\nI will present a classification result for Lagrangian fibrations of
hyper-Kähler manifolds of K3^[n] and Kum_n types up to Tate-Shafarevich
twist/degenerate twistor deformation. This improvement on the work of Mark
man is made possible by a recent breakthrough of Verbitsky-Soldatenkov whi
ch ensures that a degenerate twistor deformation of a Lagrangian fibration
is Kähler. As a consequence\, we prove that the only isotrivial Lagrangi
an fibrations of hyper-Kähler manifolds of K3^[n] and Kum_n type are the
obvious ones. This is joint work with Yoonjoo Kim and Radu Laza.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/129/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Panos Dimakis
DTSTART:20241129T160000Z
DTEND:20241129T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/130
DESCRIPTION:Title: On a conjecture of Simpson\nby Panos Dimakis as part of CRM -
Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115
.\n\nAbstract\nOn a compact Riemann surface $\\Sigma$ of genus $g>1$ equip
ped with a complex vector bundle $E$ of rank two and degree zero\, let $M_
H$ be the moduli space of Higgs bundles. $M_H$ admits a $\\mathbb C^{\\sta
r}$-action and to each stable $\\mathbb C^{\\star}$-fixed point $[(\\bar\\
partial_0\,\\Phi_0)]$ is associated a holomorphic Lagrangian submanifold $
W^1(\\bar\\partial_0\,\\Phi_0)$ inside the de Rham moduli space $M_{dR}$ o
f complex flat connections on $E$. In this talk I will give a proof of a c
onjecture of Simpson stating that $W^1(\\bar\\partial_0\,\\Phi_0)$ is clos
ed inside $M_{dR}$.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/130/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Caleb Jonker
DTSTART:20241206T160000Z
DTEND:20241206T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/131
DESCRIPTION:Title: Curvatures in generalized Kähler geometry\nby Caleb Jonker as
part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture
held in PK-5115.\n\nAbstract\nGeneralized Kähler geometry is an extension
of Kähler geometry\, with origins in supersymmetric string theory\, whic
h involves a pair of Hermitian complex structures on a Riemannian manifold
or\, equivalently\, a pair of generalized complex structures on an exact
Courant algebroid. I will introduce the various curvatures that appear in
generalized Kähler geometry\, and give some relations between them. In pa
rticular\, I will explain how the generalized Kähler-Ricci flow is relate
d to the canonical bundles of the two generalized complex structures.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/131/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chung-Ming Pan (UQAM)
DTSTART:20250110T160000Z
DTEND:20250110T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/132
DESCRIPTION:Title: Singular Gauduchon metrics and Hermite-Einstein problem on non-Kä
hler varieties\nby Chung-Ming Pan (UQAM) as part of CRM - Séminaire d
u CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstrac
t\nGauduchon metrics are very useful generalizations of Kähler metrics in
non-Kähler geometry\, as Gauduchon proved that these special metrics alw
ays exist on compact complex manifolds. One of their important application
s is defining the notion of stability for vector bundles/sheaves on non-K
ähler manifolds. It also leads the study of the existence of Hermite-Eins
tein metrics and the classification of non-Kähler surfaces. In this talk\
, I will first introduce the singular version of Gauduchon's theorem and i
ts application to the Hermite-Einstein problem for stable reflexive sheave
s on non-Kähler normal varieties. Then\, I will explain one of the main t
echnical points that lies in obtaining uniform Sobolev inequalities for pe
rturbed hermitian metrics on a resolution of singularities.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/132/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Patricia Sorya (UQAM)
DTSTART:20250117T160000Z
DTEND:20250117T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/133
DESCRIPTION:Title: Borner les chirurgies de Dehn non caractérisantes non entières\nby Patricia Sorya (UQAM) as part of CRM - Séminaire du CIRGET / Géom
étrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nNous discuton
s d'avancées vers une conjecture de McCoy stipulant que tout nœud ne pos
sède qu'au plus un nombre fini de chirurgies de Dehn non entières qui ne
le caractérisent pas. En combinant des idées de topologie géométrique
et des calculs de complexes de Floer de nœuds\, nous trouvons une régio
n bornée contenant tous les coefficients de chirurgie de Dehn non entiers
non caractérisants pour la vaste majorité des 1 701 935 nœuds avec au
plus 16 croisements.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/133/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Katherine Goldman (McGill Univ.)
DTSTART:20250207T160000Z
DTEND:20250207T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/134
DESCRIPTION:Title: Residual properties of 2-dimensional Artin groups\nby Katherin
e Goldman (McGill Univ.) as part of CRM - Séminaire du CIRGET / Géométr
ie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nIt is a longstand
ing open question to determine which Artin groups are residually finite. P
ast results have followed from linearity (e.g.\, for spherical-type or vir
tually cocompact special Artin groups) or product decompositions in rank 3
. We present a new approach to this problem using intermediate quotients t
o so-called Shephard groups. These Shephard groups possess their own inter
esting (and sometimes counterintuitive) geometry which we can leverage to
give new information about their corresponding Artin groups in some cases.
As a highlight of this connection\, we show that an Artin group which is
simultaneously 2-dimensional\, hyperbolic-type\, and FC-type is residually
finite. One of the key features of the proof we will discuss is the fact
that hyperbolic-type 2-dimensional Shephard groups are relatively hyperbol
ic\, which is almost never true of Artin groups.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/134/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jean Pierre Mutanguha (McGill Univ.)
DTSTART:20250131T160000Z
DTEND:20250131T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/135
DESCRIPTION:Title: Canonically decomposing fibrations: 3-manifolds & groups\nby J
ean Pierre Mutanguha (McGill Univ.) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/135/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ana Balibanu (Louisiana State Univ.)
DTSTART:20250221T160000Z
DTEND:20250221T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/136
DESCRIPTION:Title: Transversal slices in quasi-Poisson manifolds\nby Ana Balibanu
(Louisiana State Univ.) as part of CRM - Séminaire du CIRGET / Géométr
ie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nQuasi-Poisson man
ifolds are multiplicative generalizations of ordinary Poisson manifolds in
which the Jacobi identity is twisted by the action of a group. We study a
class of transversal slices to this group action which are motivated by g
eometric representation theory. We show that these transversal slices can
be thought of as Hamiltonian reductions of the ambient quasi-Poisson struc
ture\, and we use this to construct examples of old and new Poisson struct
ures in representation theory. This is joint work with Maxence Mayrand.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/136/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yannick Sire (John Hopkins Univ.)
DTSTART:20250404T150000Z
DTEND:20250404T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/137
DESCRIPTION:Title: Harmonic maps between singular spaces\nby Yannick Sire (John H
opkins Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topol
ogie\n\nLecture held in PK-5115.\n\nAbstract\nAfter reviewing briefly the
classical theory of harmonic maps between smooth manifolds\, I will descri
be some recent results related to harmonic maps with free boundary\, emp
hasizing on two different approaches based on recent developments by Da Li
o and Riviere. This latter approach allows in particular to give another f
ormulation which is well-suited for such maps between singular spaces. Aft
er the works of Gromov\, Korevaar and Schoen\, harmonic maps between singu
lar spaces have been instrumental to investigate super-rigidity in geometr
y. I will report on recent results where we introduce a new energy between
singular spaces and prove a version of Takahashi’s theorem (related to
minimal immersions by eigenfunctions) on RCD spaces.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/137/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mehdi Lejmi (CUNY)
DTSTART:20250411T150000Z
DTEND:20250411T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/138
DESCRIPTION:Title: Balanced HKT metrics.\nby Mehdi Lejmi (CUNY) as part of CRM
- Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-51
15.\n\nAbstract\nBalanced HKT metrics in hypercomplex geometry are thoug
ht to be the quaternionic analog of Calabi-Yau metrics in Kahler geometry.
In this talk\, first we prove the openness of balanced HKT cone inside
the cone of HKT structures on a compact hypercomplex manifold. We also s
tudy the Lie algebra of hyperholomorphic vector fields. For instance\, we
prove a harmonicity property for forms dual to hyperholomorphic vector fie
lds. This is a joint with Giovanni Gentili.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/138/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Richard Melrose (MIT)
DTSTART:20250425T150000Z
DTEND:20250425T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/139
DESCRIPTION:by Richard Melrose (MIT) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/139/
END:VEVENT
BEGIN:VEVENT
SUMMARY:François Nicoleau (Univ. de Nantes)
DTSTART:20250502T150000Z
DTEND:20250502T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/140
DESCRIPTION:Title: Global counterexamples to uniqueness for a Calder\\'on problem w
ith smooth conductivities.\nby François Nicoleau (Univ. de Nantes) as
part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture
held in PK-5115.\n\nAbstract\nLet $\\Omega \\subset \\R^n$\, $n \\geq 3$\
, be a fixed smooth bounded domain\, and let $\\gamma$ be a smooth conduct
ivity in $\\overline{\\Omega}$. Consider a non-zero frequency\n$\\lambda_0
$ which does not belong to the Dirichlet spectrum of $L_\\gamma = -{\\rm d
iv} (\\gamma \\nabla \\cdot)$. Then\, there exists an infinite number of p
airs of smooth non-isometric conductivities $(\\gamma_1\, \\gamma_2)$ on $
\\overline{\\Omega}$\, which are close to $\\gamma$ and such that the ass
ociated DN maps at frequency $\\lambda_0$ are identical.\n\nThis is a joi
nt work with Thierry Daudé\, Bernard Helffer and Niky Kamran.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/140/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xi Chen (Univ of Alberta)
DTSTART:20250314T150000Z
DTEND:20250314T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/141
DESCRIPTION:Title: Cuspidal curves on K3 surfaces\nby Xi Chen (Univ of Alberta) a
s part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture
held in PK-5115.\n\nAbstract\nA cusp is a curve singularity that is local
ly irreducible. A\ncuspidal curve is a curve with only cusps as singularit
ies.\nTopologically\, a cuspidal curve is homeomorphic to its normalizatio
n.\nRational cuspidal curves on the projective plane have been extensively
\nstudied classically. Rational curves with one\, two and three cusps\nwer
e explicitly constructed. It is known that the number of cusps of\nthese c
urves are bounded\, regardless of the degree of the curve. It is\nconjectu
red that there are no rational cuspidal plane curves with 5 or\nmore cusps
. On the other hand\, the degrees of these curves are\nunbounded. We will
study rational cuspidal curves on K3 surfaces. On\nK3 surfaces\, there is
actually an upper bound for the degree of these\ncurves. This is a joint w
ork with Frank Gounelas.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/141/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Roberto Albesiano (Univ. of Waterloo)
DTSTART:20250328T150000Z
DTEND:20250328T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/142
DESCRIPTION:Title: From division to extension\nby Roberto Albesiano (Univ. of Wat
erloo) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\
nLecture held in PK-5115.\n\nAbstract\nExtending holomorphic data from sub
varieties (L2 extension) and lifting holomorphic sections of quotient bund
les (L2 division) are fundamental problems in complex geometry and several
complex variables. They are also intimately related: in fact\, Ohsawa sh
owed that a version of the L2 division theorem can be proved as a corollar
y of the L2 extension theorem. We will see how\, conversely\, a version o
f the extension theorem can be obtained as an easy corollary of a division
theorem with bounded generators.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/142/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kuan-Hui Lee (Univ. California\, Irvine)
DTSTART:20250509T150000Z
DTEND:20250509T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/143
DESCRIPTION:Title: The stability of steady pluriclosed soliton\nby Kuan-Hui Lee (
Univ. California\, Irvine) as part of CRM - Séminaire du CIRGET / Géomé
trie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nNon-Kähler Cal
abi-Yau theory is a newly developed subject and it arises naturally in mat
hematical physics and generalized geometry. The relevant geometries are pl
uriclosed metrics which are critical points of the generalized Einstein–
Hilbert action which is an extension of Perelman’s F-functional. In this
talk\, we studied the non-Kähler Calabi-Yau through pluriclosed flow whi
ch was first introduced by Streets and Tian a few years ago. We study the
critical points of the generalized Einstein-Hilbert action and discuss the
stability of critical points which are defined as pluriclosed steady soli
tons. We proved that all compact Bismut–Hermitian–Einstein metrics are
linearly stable.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/143/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Changjie Chen (Université de Montréal)
DTSTART:20250919T150000Z
DTEND:20250919T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/144
DESCRIPTION:Title: Morse theory on moduli spaces\nby Changjie Chen (Université d
e Montréal) as part of CRM - Séminaire du CIRGET / Géométrie et Topolo
gie\n\nLecture held in PK-5115.\nAbstract: TBA\n\nSarnak conjectured in th
e 1990s that the determinant of the Laplacian is a Morse function on the s
pace of unit area Riemannian metrics on a given surface\, and hence induce
s a Morse function on the moduli space of Riemann surfaces.\n\nIt is known
that the systole function\, defined as the length of a shortest closed ge
odesic with respect to the base metric\, is topologically Morse on the mod
uli space M_{g\,n}. However\, it does not generate a Morse theory.\n\nIn t
his talk\, I will introduce a family of Morse functions\, defined as weigh
ted exponential averages of all geodesic-length functions\, on the Deligne
-Mumford compactification (M_{g\,n} bar). These functions are compatible w
ith the Deligne-Mumford stratification and the Weil-Petersson metric\, and
their critical points can be characterized by a combinatorial property.\n
\nI will finally talk about homological consequences of hyperbolic geometr
y results via Morse theory\, including a stability theorem. If time permit
s\, I will explain how these Morse functions connect to Sarnak’s conject
ure.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/144/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mike Roth (Queens University)
DTSTART:20251003T150000Z
DTEND:20251003T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/145
DESCRIPTION:Title: Reduced Čech complexes and computing higher direct images under t
oric fibrations.\nby Mike Roth (Queens University) as part of CRM - S
éminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.
\n\nAbstract\nLet $X$ be a topological space\, $F$ a sheaf of abelian grou
ps on $X$\, and $\\{ U_{\\alpha}\\}_{\\alpha\\in I\\}$ an open cover of $X
$. Then one can form a Čech complex\, a complex of groups built from the
values of $F$ on the open sets and their intersections. \n\nIf the hig
her cohomology of $F$ vanishes on all these open sets\, then it is a well-
known theorem of Leray that this complex computes the cohomology of $F$ on
$X$. For instance\, if $X$ is a manifold and the $U_{\\alpha}$ form a `
good cover’ (all the $U_{\\alpha}$ and their intersections are homeomorp
hic to $\\mathbb{R}^n$)\, then the Čech complex can be used to compute th
e topological cohomology of $X$.\n\nFor special kinds of toric varieties
— those whose fans are `simplicial’ -- it is known how to construct sm
aller (“reduced”) complexes which still correctly compute cohomology o
f sheaves.\n\nThis talk has three main goals : (1) To give an axiomatizati
on of ‘reduced Čech complexes’\, valid for any topological space\; (
2) To extend the previous construction of reduced Čech complexes to all c
ompact toric varieties (not just simplicial ones)\, and more generally to
’semi-proper’ toric varieties\; (3) To use the previous method to give
an algorithm for computing higher direct images (roughly the `cohomology
along the fibres’) of line bundles for toric fibrations between smooth t
oric varieties.\n\nNo previous knowledge of toric varieties is required.\n
This is joint work with Sasha Zotine.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/145/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dylan Cant (Université de Montréal)
DTSTART:20251017T150000Z
DTEND:20251017T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/146
DESCRIPTION:Title: Equivariant quantum cohomology for Lagrangian submanifolds\nby
Dylan Cant (Université de Montréal) as part of CRM - Séminaire du CIRG
ET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nSup
pose that M is a symplectic manifold equipped with an involution preservin
g the symplectic structure\, and suppose L is a compact Lagrangian submani
fold of M preserved by the involution. A central question in symplectic to
pology concerns the existence of intersections between L and f(L)\, where
f is a Hamiltonian motion (the time 1 map of a Hamiltonian isotopy). We wi
ll explore additional rigidity exhibited by Hamiltonian motions which are
equivariant with respect to the involution. As an example\, we show the pr
oduct of the n unit circles (in R2n) is not displaceable by a Hamiltonian
motion commuting with the antipodal map z→-z.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/146/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Octav Cornea (Université de Montréal)
DTSTART:20251107T160000Z
DTEND:20251107T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/147
DESCRIPTION:Title: Approximability and Gromov width of Lagrangians\nby Octav Corn
ea (Université de Montréal) as part of CRM - Séminaire du CIRGET / Géo
métrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI will descr
ibe recent work joint with Giovanni Ambrosioni and\nPaul Biran ( both from
ETH) that ties certain bounds of Lagrangian Gromov \nwidth to a categori
fied notion of approximability first introduced by Alan\nTuring in the s
tudy of Lie groups.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/147/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Steven Rayan
DTSTART:20251117T160000Z
DTEND:20251117T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/148
DESCRIPTION:Title: Hyperbolic Band Structures and Moduli Spaces\nby Steven Rayan
as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLectur
e held in PK-5675.\n\nAbstract\nI will discuss my recent works involving t
he use of ideas from differential and complex algebraic geometry to antici
pate new models of 2-dimensional quantum materials\, generalizing topologi
cal materials\, with an emphasis on the development of a hyperbolic analog
ue of electronic band theory. In the process\, we will develop a diction
ary between well-known moduli spaces of data on Riemann surfaces on the on
e side and condensed matter properties on the other\, with a view to invar
iants encoding physical behaviours. I will briefly outline recent attempts
to synthesize such materials in my recent collaborations with experimenta
l and engineering physicists.\n\nNote : The room is PK-5675 and the date :
Monday 17th of November.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/148/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shih-Kai Chiu (University of California\, Irvine)
DTSTART:20251121T160000Z
DTEND:20251121T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/149
DESCRIPTION:Title: Special Lagrangian submanifolds from tropical-like data\nby Sh
ih-Kai Chiu (University of California\, Irvine) as part of CRM - Séminair
e du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbst
ract\nSpecial Lagrangian submanifolds are volume-minimizing Lagrangians in
Calabi-Yau manifolds. Their existence not only provides a rich source of
higher-codimensional minimal submanifolds\, but also plays a central role
in the SYZ picture of mirror symmetry. However\, existence results remain
scarce\, especially in the compact case. In this talk\, I will present two
gluing constructions: (1) special Lagrangians in K3-fibered Calabi-Yau 3-
folds\, and (2) special Lagrangians in the simplest SYZ fibration\, $T^*T^
n$. In both cases\, the starting point is a tropical-like graph in the bas
e of the fibration\, which guides the gluing of local models. Based on joi
nt works with Yang Li and Yu-Shen Lin.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/149/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tristan Collins (University of Toronto)
DTSTART:20251128T160000Z
DTEND:20251128T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/150
DESCRIPTION:Title: Complete Calabi-Yau Manifolds and Optimal Transportation\nby T
ristan Collins (University of Toronto) as part of CRM - Séminaire du CIRG
ET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI w
ill discuss some geometric\, analytic and algebraic\, aspects of complete
Calabi-Yau metrics on pairs (X\,D) where X is Fano and D is an ample anti-
canonical divisor with simple normal crossings. I will highlight the conn
ection between existence of such Calabi-Yau metrics and optimal boundary r
egularity theory for optimal transportation.\nThis talk is based on joint
works with Y. Li\, F. Tong\, S.-T. Yau\, and H. Guenancia\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/150/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Junsheng Zhang (Courant Institute\, NYU)
DTSTART:20251205T160000Z
DTEND:20251205T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/151
DESCRIPTION:Title: Diameter lower bounds for the Kähler–Ricci flow at finite-time
singularities\nby Junsheng Zhang (Courant Institute\, NYU) as part of
CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in P
K-5115.\n\nAbstract\nWe establish a uniform lower bound for the diameter a
long the Kähler–Ricci flow up to the first finite-time singularity for
non-Fano initial data. The argument is based on a weak transcendental base
-point-freeness result on compact Kähler manifolds and a generalized Schw
arz-type lemma.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/151/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christophe Mourougane (Université de Rennes)
DTSTART:20251024T150000Z
DTEND:20251024T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/152
DESCRIPTION:Title: Jet differentials and applications\nby Christophe Mourougane (
Université de Rennes) as part of CRM - Séminaire du CIRGET / Géométrie
et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nJet differentials o
n complex manifolds are geometric objects that formalize algebraic differe
ntial equations. \nThey are useful in Kobayashi's theory of hyperbolicity\
, where we seek\, for example\, to show the algebraic degeneration of enti
re curves on projective manifolds of general type.\nIn this talk\, based o
n work in progress with Pierre-Emmanuel Chaput and Lionel Darondeau\, I wi
ll present a construction of jet differentials and some ideas to prove the
completeness of the resulting system.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/152/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jérôme Vétois (McGill)
DTSTART:20260116T160000Z
DTEND:20260116T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/153
DESCRIPTION:Title: Nonexistence of extremals for the second conformal eigenvalue in l
ow dimensions\nby Jérôme Vétois (McGill) as part of CRM - Séminair
e du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbst
ract\nIn this talk\, we will consider the second conformal eigenvalue on a
closed Riemannian manifold of positive Yamabe type and dimension greater
than or equal to 3. The second conformal eigenvalue is defined as the infi
mum of the second eigenvalue of the conformal Laplacian in a conformal cla
ss of metrics with renormalized volume. We will discuss a recent result sh
owing that this infimum is not attained for metrics close to the round met
ric on the sphere in dimensions 3 to 10\, which contrasts sharply with the
situation in dimensions greater than or equal to 11\, where Ammann and Hu
mbert obtained the existence of minimizers on any closed nonlocally confor
mally flat manifold. This is a joint work with Bruno Premoselli (Universit
é Libre de Bruxelles).\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/153/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chenxi Yin (UQAM)
DTSTART:20260130T160000Z
DTEND:20260130T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/154
DESCRIPTION:Title: Relative uniform Yau-Tian-Donaldson correspondence for projective
bundles over a curve\nby Chenxi Yin (UQAM) as part of CRM - Séminaire
du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstr
act\nIn this talk\, I will present recent joint work with Simon Jubert on
a version of the Yau–Tian–Donaldson correspondence for projective bund
les Y=P(E) over a curve. By earlier work of Apostolov–Keller\, if a Käh
ler class on Y admits an extremal Kähler metric\, then E must split as a
direct sum of stable vector bundles. We show that\, for such E\, a Kähler
class on Y admits an extremal Kähler metric if and only if it is relativ
ely uniformly K-stable. The proof uses a distinguished family of test conf
igurations\, called compatible test configurations\, constructed from the
horospherical symmetry of the fibers\, together with the framework of weig
hted constant scalar curvature Kähler metrics.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/154/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tyrone Ghaswala (University of Waterloo)
DTSTART:20260213T160000Z
DTEND:20260213T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/155
DESCRIPTION:Title: Big mapping class groups and uniqueness of Polish structures\n
by Tyrone Ghaswala (University of Waterloo) as part of CRM - Séminaire du
CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract
\nSuppose you are given a topological group. You may wonder about how much
the group structure determines the topology. At first glance\, the answer
appears to be "not very much at all"\, since every topological group admi
ts the discrete topology\, and the trivial topology\, both of which are co
mpatible with the group operation. \n\nMapping class groups of infinite-ty
pe surfaces are humungous (not a technical term)\, and come equipped with
a Polish topology. We can ask a refinement of the above question: How much
does the group structure of a mapping class group determine its Polish to
pology? In this talk we'll investigate this question\, leading to a perhap
s surprising answer.\n\nThis is joint work with Sumun Iyer\, Robbie Lyman\
, and Nick Vlamis.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/155/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Robert Harris (UQAM)
DTSTART:20260220T160000Z
DTEND:20260220T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/156
DESCRIPTION:Title: Recipes for exotic definite 4-manifolds\nby Robert Harris (UQA
M) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLec
ture held in PK-5115.\n\nAbstract\nIt is an ongoing search to find an exot
ic manifold which is homeomorphic to a sum of complex projective planes (o
r a sum with only oppositely oriented projective planes). Relaxing this c
ondition\, a smooth definite manifold is one with an intersection form at
least isomorphic to that of such a space. The door into the study of defin
ite exotica was first opened by the discovery of examples with a fundame
ntal group of order two by Levine\, Lidman and Piccirillo and further adva
ncements have since been made to construct examples with larger fundamenta
l groups. We will discuss the general recipe for constructing these manifo
lds\, as well as the specific ingredients that different researchers have
been using. This is based on joint work with Patrick Naylor and B. Doug Pa
rk.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/156/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ronan Conlan (UT Dallas)
DTSTART:20260227T160000Z
DTEND:20260227T171500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/157
DESCRIPTION:Title: On Toric Shrinking Gradient Kähler-Ricci Solitons\nby Ronan C
onlan (UT Dallas) as part of CRM - Séminaire du CIRGET / Géométrie et T
opologie\n\nLecture held in PK-5115.\n\nAbstract\nShrinking gradient Kähl
er-Ricci solitons model finite-time singularities of the Kähler-Ricci flo
w on compact Kähler manifolds. I will discuss the existence problem for s
hrinking gradient Kähler-Ricci solitons in the non-compact toric setting.
This talk is based on joint work with Ivin Babu and Alix Deruelle\, and w
ith Charles Cifarelli and Alix Deruelle.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/157/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mauricio Bustamente (UQAM)
DTSTART:20260313T150000Z
DTEND:20260313T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/158
DESCRIPTION:Title: Strict hyperbolization of flat manifolds\nby Mauricio Bustamen
te (UQAM) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie
\n\nLecture held in PK-5115.\n\nAbstract\nCharney–Davis strict hyperboli
zation is a construction that takes a nonpositively curved cube complex an
d converts it into a negatively curved space. In this talk\, I’ll explai
n how strict hyperbolization can be used to produce closed hyperbolic mani
folds with interesting topological features\, by applying it to a suitable
class of flat manifolds. This leads to new examples of closed hyperbolic
manifolds with nontrivial Pontryagin and Stiefel–Whitney classes\, hyper
bolic manifolds that arise as totally geodesic boundaries of other hyperbo
lic manifolds\, and aspherical topological manifolds that admit no smooth
structure. This is joint work with Eduardo Reyes and Stefano Riolo.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/158/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yu-Chi Hou (Univ. of Maryland)
DTSTART:20260327T150000Z
DTEND:20260327T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/159
DESCRIPTION:Title: Kähler Quantization in Degenerate Setting\nby Yu-Chi Hou (Uni
v. of Maryland) as part of CRM - Séminaire du CIRGET / Géométrie et Top
ologie\n\nLecture held in PK-5115.\n\nAbstract\nKähler quantization provi
des a bridge between infinite-dimensional geometric objects in Kähler geo
metry and finite-dimensional data arising from spaces of holomorphic secti
ons. In this talk\, I will first review this correspondence in the ample c
ase\, where it is well understood and plays a central role in the study of
canonical metrics.\nI will then explain how this picture can be extended
beyond the ample setting\, where smooth positively curved metrics are no l
onger available. In particular\, I will describe how the Monge–Ampère e
nergy can still be recovered from finite-dimensional approximations in the
semipositive and big setting. Finally\, if time permits\, I will outline
the idea of the proof.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/159/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hans Boden (McMaster Univ.)
DTSTART:20260417T150000Z
DTEND:20260417T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/160
DESCRIPTION:by Hans Boden (McMaster Univ.) as part of CRM - Séminaire du
CIRGET / Géométrie et Topologie\n\nInteractive livestream: https://uqam.
zoom.us/j/88383789249\nLecture held in PK-5115.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/160/
URL:https://uqam.zoom.us/j/88383789249
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mike Miller Eismeier (Vermont Univ.)
DTSTART:20260424T150000Z
DTEND:20260424T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/161
DESCRIPTION:by Mike Miller Eismeier (Vermont Univ.) as part of CRM - Sémi
naire du CIRGET / Géométrie et Topologie\n\nInteractive livestream: http
s://uqam.zoom.us/j/88383789249\nLecture held in PK-5115.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/161/
URL:https://uqam.zoom.us/j/88383789249
END:VEVENT
BEGIN:VEVENT
SUMMARY:Charlie Cifarelli (Stony Brook University)
DTSTART:20260320T150000Z
DTEND:20260320T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/162
DESCRIPTION:Title: K-polystability of asymptotically conical Kähler-Ricci shrinkers<
/a>\nby Charlie Cifarelli (Stony Brook University) as part of CRM - Sémin
aire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nA
bstract\nShrinking gradient Kähler-Ricci solitons (Kähler-Ricci shrinker
s) are fundamental objects in the study of the Kähler-Ricci flow\, charac
terizing much of the behavior of finite-time singularities. Recently\, Sun
--Zhang have developed an algebraic theory for Kähler-Ricci shrinkers\, w
hich in particular implies that such spaces are naturally quasiprojective
varieties. Moreover\, they propose a YTD correspondence between the existe
nce of such a metric and an algebro-geometric notion of K-stability\, anal
ogous to and in fact extending the well-known situations for Fano manifold
s and Kähler cones. In this talk\, I will discuss the proof of one direc
tion of the correspondence\, namely that the existence of a Kähler-Ricci
shrinker metric implies K-polystability\, in the case that the Ricci curva
ture decays at infinity. This is joint work with Carlos Esparza.\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/162/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Calderbank
DTSTART:20260410T150000Z
DTEND:20260410T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/163
DESCRIPTION:by David Calderbank as part of CRM - Séminaire du CIRGET / G
éométrie et Topologie\n\nInteractive livestream: https://uqam.zoom.us/j/
88383789249\nLecture held in PK-5115.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/163/
URL:https://uqam.zoom.us/j/88383789249
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bob Olivier (Université Sorbonne Paris Nord)
DTSTART:20260529T150000Z
DTEND:20260529T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/164
DESCRIPTION:Title: The local structure of finite groups and of their classifying spac
es\nby Bob Olivier (Université Sorbonne Paris Nord) as part of CRM -
Séminaire du CIRGET / Géométrie et Topologie\n\nInteractive livestream:
https://uqam.zoom.us/j/88383789249\nLecture held in PK-5115.\n\nAbstract\
nFix a prime ${p}$. We say that two finite groups $G$ and\n$H$ are ``${p}$
-equivalent'' if there is an isomorphism between\nSylow $p$-subgroups $S \
\in Syl_p(G)$ and $T\\in \nSyl_p({H})$ that preserves all $G-$ and\n${H}-$
conjugacy relations among elements and subgroups of $S$\nand $T$. We say t
hat two topological spaces ${X}$ and ${Y}$ are ``${p}$-equivalent'' if the
re is a third space ${Z}$\, and maps $X\\to Z \\leftarrow Y$ that induce i
somorphisms in homology\nwith coefficients in $\\mathbb{Z}/p$. (Both of th
ese are equivalence\nrelations.) The main theorem I want to describe says
that finite groups ${G}$ and ${H}$ are\n$p$-equivalent (as groups) if and
only if their classifying spaces\nare ${p}$-equivalent (as spaces).\n\n\nI
will start by defining in more detail classifying spaces of discrete\ngro
ups and the two kinds of ${p}$-equivalence described above\, and\nalso say
ing a little about the background of the theorem. I then plan to\ngive som
e examples of finite groups that are ${p}$-locally equivalent\nbut not iso
morphic\, and say something about ideas that went into the\nproof of the t
heorem (carried out by several different people over a\nperiod of 10--15 y
ears).\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/164/
URL:https://uqam.zoom.us/j/88383789249
END:VEVENT
BEGIN:VEVENT
SUMMARY:Qi Yao (Stony Brook)
DTSTART:20260508T150000Z
DTEND:20260508T161500Z
DTSTAMP:20260404T024900Z
UID:CIRGET/165
DESCRIPTION:by Qi Yao (Stony Brook) as part of CRM - Séminaire du CIRGET
/ Géométrie et Topologie\n\nInteractive livestream: https://uqam.zoom.us
/j/88383789249\nLecture held in PK-5115.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/CIRGET/165/
URL:https://uqam.zoom.us/j/88383789249
END:VEVENT
END:VCALENDAR