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BEGIN:VEVENT
SUMMARY:Olivier Glorieux (IHES)
DTSTART:20200519T140000Z
DTEND:20200519T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/1
DESCRIPTION:Title: Critical exponents in higher rank symmetric spaces\nby Olivier
Glorieux (IHES) as part of Pangolin seminar\n\n\nAbstract\nThe aim of the
talk is to present some recent results on critical exponents for discrete
subgroups of higher rank semisimple Lie groups. We will survey classical
results in negative curvature\, the relationship with entropy and the Haus
dorff dimension of limit sets. Then we will introduce the geometric proper
ties of higher rank symmetric spaces and explain the main differences with
strict negative curvature. We will focus on two different results : the b
ehaviour of the critical exponent under normal subgroup (j.w. S. Tapie) an
d the extension of classical results to pseudo-riemannian geometry (j.w. D
. Monclair).\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Roman Prosanov (Technische Universität Wien)
DTSTART:20200602T140000Z
DTEND:20200602T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/2
DESCRIPTION:Title: Rigidity of compact Fuchsian manifolds with convex boundary\nb
y Roman Prosanov (Technische Universität Wien) as part of Pangolin semina
r\n\n\nAbstract\nBy a compact Fuchsian manifold with boundary we mean a hy
perbolic 3-manifold homeomorphic to $S_g \\times [0\; 1]$ such that the bo
undary component $S_g \\times \\{ 0\\}$ is geodesic. Here $S_g$ is a close
d oriented surface of genus $g>1$. Fuchsian manifolds are known as toy cas
es in the study of geometry of hyperbolic 3-manifolds with boundary. In my
talk I will sketch a proof that a compact Fuchsian manifold with convex b
oundary is uniquely determined by the induced path metric on $S_g \\times
\\{1\\}$. We do not put further restrictions on the boundary except convex
ity. This unifies two previously known results: in the case of smooth boun
dary such a result follows from a work of Schlenker and in the case of pol
yhedral boundary it was proven by Fillastre.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gabriel Calsamiglia (Universidade Federal Fluminense)
DTSTART:20200616T140000Z
DTEND:20200616T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/3
DESCRIPTION:Title: Spaces of isoperiodic holomorphic and meromorphic differentials\nby Gabriel Calsamiglia (Universidade Federal Fluminense) as part of Pan
golin seminar\n\n\nAbstract\nI will present some results on the topology o
f the spaces of holomorphic and meromorphic one forms over complex curves
for which integration along certain homology classes is constant.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrea Seppi (Université Grenoble Alpes)
DTSTART:20200714T140000Z
DTEND:20200714T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/4
DESCRIPTION:Title: The Gauss map for nearly-Fuchsian manifolds\nby Andrea Seppi (
Université Grenoble Alpes) as part of Pangolin seminar\n\n\nAbstract\nIn
this talk we will study the Gauss map for nearly-Fuchsian manifolds\, name
ly complete hyperbolic n-manifolds homeomorphic to HxR\, where H is a clos
ed hypersurface with principal curvatures smaller than one in absolute val
ue. The Gauss map of such a hypersurface is a Lagrangian equivariant embed
ding in the space of oriented geodesics of hyperbolic space\, which is kno
wn to have a natural para-Kähler structure. We will present two character
izations of the Lagrangian equivariant embeddings obtained in this way\, t
he first in terms of the vanishing of the Maslov class\, and the second in
terms of orbits of the group of Hamiltonian symplectomorphisms.\n\nThis i
s joint work with Christian El Emam (Pavia).\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dmitry Faifman (Tel-Aviv Universty)
DTSTART:20200728T140000Z
DTEND:20200728T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/6
DESCRIPTION:Title: Intrinsic volumes of submanifolds of normed spaces: How intrinsic
are they?\nby Dmitry Faifman (Tel-Aviv Universty) as part of Pangolin
seminar\n\n\nAbstract\nThe intrinsic volumes\, or quermassintegrals\, are
certain geometric functionals on sufficiently nice subsets of Euclidean sp
ace\, given by the coefficients of the volume of an epsilon-tube of the se
t\, which is a polynomial in epsilon. H. Weyl discovered that their value
on a Riemannian submanifold of Euclidean space is\, remarkably\, an intrin
sic invariant of the metric. We will consider the setting of a normed spac
e\, where the Holmes-Thompson intrinsic volumes are available\, and attemp
t to extend Weyl's result to Finsler submanifolds. \nBased on a joint work
with T. Wannerer.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Graham Smith (Universidade Federal do Rio de Janeiro)
DTSTART:20200630T140000Z
DTEND:20200630T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/8
DESCRIPTION:Title: On eternal forced mean curvature flows of tori in perturbations of
the unit sphere\nby Graham Smith (Universidade Federal do Rio de Jane
iro) as part of Pangolin seminar\n\n\nAbstract\nUsing a singular perturbat
ion argument based on the work of B. White\, we construct eternal mean cur
vature flows of tori in perturbations of the standard unit 3-sphere. Besid
es being of interest in the theory of mean curvature flows\, such objects
have applications in Morse homology theory. A large part of the proof invo
lves the construction of certain types of functions of Morse-Smale type ov
er the moduli space of Clifford tori. This has interesting potential appli
cations to the theory of Radon transformations. This is joint work with Cl
audia Salas Mangaño.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gilles Carron (Université de Nantes)
DTSTART:20200825T140000Z
DTEND:20200825T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/9
DESCRIPTION:Title: The index theorem for manifolds with cusps\nby Gilles Carron (
Université de Nantes) as part of Pangolin seminar\n\n\nAbstract\nI will s
peak on the result obtained with W. Ballmann and J. Brüning about index t
heorem on manifold with cusps :\n\n-Eigenvalues and holonomy. Int. Math. R
es. Not. 2003\, no. 12\, 657–665.\n\n-Regularity and index theory for Di
rac-Schrödinger systems with Lipschitz coefficients.\n\nJ. Math. Pures Ap
pl. (9) 89 (2008)\, no. 5\, 429–476.\n\n-Index theorems on manifolds wit
h straight ends. Compos. Math. 148 (2012)\, no. 6\, 1897–1968.\n\nI will
start with a review of the case of compact manifolds and manifolds with c
ylindrical ends (i.e. the work of Atiyah-Patodi-Singer) and then describe
the main technical difficulties we had to face.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Martín Reiris (Universidad de la República\, Montevideo)
DTSTART:20200908T133000Z
DTEND:20200908T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/10
DESCRIPTION:Title: On the existence of Killing fields in smooth spacetimes with a co
mpact Cauchy horizon\nby Martín Reiris (Universidad de la República\
, Montevideo) as part of Pangolin seminar\n\n\nAbstract\nWe prove that the
surface gravity of a compact non-degenerate Cauchy horizon in a smooth va
cuum spacetime\, can be normalized to a non-zero constant. This result\, c
ombined with a recent result by Oliver Petersen and István Rácz\, end up
proving the Isenberg-Moncrief\nconjecture on the existence of Killing fie
lds\, in the smooth differentiability class. The well known corollary of t
his\, in accordance with the strong cosmic censorship conjecture\, is that
the presence of compact Cauchy horizons is a non-generic phenomenon.\nTho
ugh we work in 3+1\, the result is valid line by line in any n+1-dimension
s.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thibault Leveufre (Université Paris-Sud)
DTSTART:20200922T140000Z
DTEND:20200922T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/11
DESCRIPTION:Title: Marked length spectrum\, geodesic stretch and pressure metric
\nby Thibault Leveufre (Université Paris-Sud) as part of Pangolin seminar
\n\n\nAbstract\nThe marked length spectrum of a negatively-curved manifo
ld is the data of all the lengths of closed geodesics\, marked by the free
homotopy of the manifold. The marked length spectrum conjecture (also kno
wn as the Burns-Katok conjecture\, 1985) asserts that two negatively-curve
d manifolds with same marked length spectrum should be isometric. This con
jecture was proved on surfaces (Croke '90\, Otal '90) but remains open in
higher dimensions. I will present a proof of a local version of this conje
cture\, based on the notions of geodesic stretch and pressure metric (
a generalization of the Weil-Petersson metric to the context of variable c
urvature). Some elements of the theory of Pollicott-Ruelle resonances and
anisotropic spaces will also be needed (I will recall everything). Joint w
ork with C. Guillarmou and G. Knieper.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stéphane Sabourau (Université Parsi-Est Créteil)
DTSTART:20201006T140000Z
DTEND:20201006T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/12
DESCRIPTION:Title: Geometric semi-norms in homology\nby Stéphane Sabourau (Univ
ersité Parsi-Est Créteil) as part of Pangolin seminar\n\n\nAbstract\nThe
simplicial volume of a simplicial complex is a topological invariant rela
ted to the growth of the fundamental group\, which gives rise to a semi-no
rm in homology. In this talk\, we introduce the volume entropy semi-norm\,
which is also related to the growth of the fundamental group of simplicia
l complexes and shares functorial properties with the simplicial volume. A
nswering a question of Gromov\, we prove that the volume entropy semi-norm
is equivalent to the simplicial volume semi-norm in every dimension. Join
t work with I. Babenko.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Filippo Mazzoli (University of Virginia)
DTSTART:20201103T140000Z
DTEND:20201103T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/13
DESCRIPTION:Title: Constant Gaussian curvature surfaces in hyperbolic 3-manifolds\nby Filippo Mazzoli (University of Virginia) as part of Pangolin seminar
\n\n\nAbstract\nIn this talk I will describe how constant Gaussian curvatu
re (CGC) surfaces interpolate the structures of the pleated boundary of th
e convex core and of the boundary at infinity of a geometrically finite hy
perbolic end\, and I will present a series of consequences of this phenome
non: a description of the renormalized volume of a quasi-Fuchsian manifold
in terms of its CGC-foliation\, a characterization of the immersion data
of CGC-surfaces of a hyperbolic end as an integral curve of a time-depende
nt Hamiltonian vector field on the cotangent space to Teichmüller space\,
and a consequent generalization of McMullen’s Kleinian reciprocity theo
rem.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bruno Premoselli (Université Libre de Bruxelles)
DTSTART:20201020T140000Z
DTEND:20201020T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/14
DESCRIPTION:Title: Glueing constructions of Compact Einstein four-manifolds with neg
ative sectional\nby Bruno Premoselli (Université Libre de Bruxelles)
as part of Pangolin seminar\n\n\nAbstract\nWe construct examples of closed
Einstein four-manifolds with negative sectional curvature. We describe tw
o main families of examples which are respectively obtained as ramified co
vers and smooth quotients of ``large’’ hyperbolic 4-manifolds with sym
metries. The first family of examples is sometimes referred to as Gromov-T
hurston manifolds. The Einstein metrics that we construct are the result o
f a glueing procedure. They are obtained as deformations of an approximate
Einstein metric which is an interpolation between a ``black-hole – type
’’ Riemannian Einstein metric near the symmetry locus and the hyperbol
ic metric. This construction yields the first example of compact Einstein
manifolds with negative sectional curvature which are not locally homogen
eous. This is a joint work with J. Fine (ULB\, Brussels).\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Duc-Manh Nguyen (Université de Bordeaux)
DTSTART:20201117T140000Z
DTEND:20201117T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/15
DESCRIPTION:Title: Variation of Hodge structure and enumerating triangulations and q
uadrangulations of surfaces\nby Duc-Manh Nguyen (Université de Bordea
ux) as part of Pangolin seminar\n\n\nAbstract\nSince the work of Eskin-Oko
unkov (in 2001)\, it has been known that in any stratum of translation sur
faces the number of square-tiled surafces constructed from at most n squar
es grows like $c\\pi^{2g}n^d$\, where $d$ is the (complex) dimension of t
he stratum\, $g$ is the genus of the surfaces\, and $c$ is a rational numb
er. Similar phenomenon also occurs in strata of quadratic differentials. C
ounting square-tiled surfaces in a given stratum is more or less the same
as counting quadrangulations of a topological surface\, with some prescrib
ed conditions on the singularities and the holonomy of the associated flat
metric. More recently\, Engel showed that the asymptotics of the numbers
of quadrangulations and triangulations\, satisfying some prescribed condit
ions at the singularities\, with at most $n$ tiles are of the form $\\alph
a n^d$\, where $\\alpha$ is a constant in $Q[\\pi]$ or $Q[\\sqrt{3}\\pi]$.
\nIn this talk\, we will explain how the asymptotics above can be related
to the computation of the volume of some moduli spaces\, and how one can s
how that in some situations the constant $\\alpha$ belongs actually to eit
her $Q\\cdot\\pi^d$\, or $Q\\cdot(\\sqrt{3}\\pi)^d$ by using tools from co
mplex algebraic geometry. This is joint work with Vincent Koziarz.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jérémy Toulisse (Université de Nice-Sophia Antipolis)
DTSTART:20201201T140000Z
DTEND:20201201T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/16
DESCRIPTION:Title: Plateau problem in the pseudo-hyperbolic space\nby Jérémy T
oulisse (Université de Nice-Sophia Antipolis) as part of Pangolin seminar
\n\n\nAbstract\nThe pseudo-hyperbolic space H^{2\,n} is the pseudo-Riemann
ian analogue of the classical hyperbolic space. In this talk\, I will expl
ain how to solve an asymptotic Plateau problem in this space: given a topo
logical circle in the boundary at infinity of H^{2\,n}\, we construct a un
ique complete maximal surface bounded by this circle. This construction re
lies on Gromov’s theory of pseudo-holomorphic curves. This is a joint wo
rk with François Labourie and Mike Wolf.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ben Lowe (Princeton University)
DTSTART:20201215T140000Z
DTEND:20201215T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/17
DESCRIPTION:Title: Minimal Surfaces in Negatively Curved 3-Manifolds and Dynamics\nby Ben Lowe (Princeton University) as part of Pangolin seminar\n\n\nAbs
tract\nThe Grassmann bundle of tangent 2-planes over a closed hyperbolic 3
-manifold M has a natural foliation by (lifts by their tangent planes of)
immersed totally geodesic planes in M. I am going to talk about work I’v
e done on constructing foliations whose leaves are (lifts of) minimal surf
aces in a metric on M of negative sectional curvature\, which are deformat
ions of the totally geodesic foliation described above. These foliations m
ake it possible to use homogeneous dynamics to study how closed minimal su
rfaces in variable negative curvature are distributed in the ambient 3-man
ifold. Many of the ideas here come from recent work of Calegari-Marques-Ne
ves\, which I will also talk about. I was able to establish some prelimina
ry facts about the dynamics of these foliations\, but much remains to be u
nderstood.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jason Lotay (Oxford University)
DTSTART:20210126T150000Z
DTEND:20210126T160000Z
DTSTAMP:20260404T110656Z
UID:Geometry/18
DESCRIPTION:Title: Deformed G2 instantons\nby Jason Lotay (Oxford University) as
part of Pangolin seminar\n\n\nAbstract\nDeformed G2-instantons are specia
l connections occurring in G2 geometry in 7 dimensions. They arise as “m
irrors” to certain calibrated cycles\, providing an analogue to deformed
Hermitian-Yang-Mills connections\, and are critical points of a Chern-Sim
ons-type functional. I will describe an elementary construction of the fir
st non-trivial examples of deformed G2-instantons\, and their relation to
3-Sasakian geometry\, nearly parallel G2-structures\, isometric G2-structu
res\, obstructions in deformation theory\, the topology of the moduli spac
e\, and the Chern-Simons-type functional.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christian El Emam (Université du Luxembourg)
DTSTART:20210209T140000Z
DTEND:20210209T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/19
DESCRIPTION:Title: Families of equivariant immersions in $H^3$ with holomorphic holo
nomy\nby Christian El Emam (Université du Luxembourg) as part of Pang
olin seminar\n\n\nAbstract\nGiven an equivariant immersion of a surface in
the hyperbolic 3-space\, a typical problem consists in understanding whet
her a deformation of the immersion (parametrized over a complex manifold)
produces a holomorphic deformation of its mondromy in PSL(2\,C). In this t
alk we present a simple “trick” providing a sufficient condition for t
his property\, offering for instance an alternative proof of the holomorph
icity of the complex landslide flow. This result is a consequence of the s
tudy of immersions into the space of geodesics of the hyperbolic 3-space\,
seen as a holomorphic Riemannian manifold\, whose key features will be di
scussed in the talk.\n\nThis is joint work with Francesco Bonsante\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:María Asunción Jiménez (Universidade Federal Fluminense)
DTSTART:20210223T140000Z
DTEND:20210223T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/20
DESCRIPTION:Title: Elliptic Linear Weingarten graphs with isolated singularities
\nby María Asunción Jiménez (Universidade Federal Fluminense) as part o
f Pangolin seminar\n\n\nAbstract\nWe study isolated singularities of graph
s whose mean and Gaussian curvature satisfy the elliptic linear relation $
2\\alpha H+\\beta K=1$\, $\\alpha^2+\\beta>0$. This family of surfaces inc
ludes convex and non-convex singular surfaces and also cusp-type surfaces.
We determine in which cases the singularity is removable\, and classify n
on-extendable totally isolated singularities in term of regular real analy
tic strictly convex curves in $\\S^2$. This is a joint work with João P.
dos Santos.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Barbara Schapira (Université de Rennes I)
DTSTART:20210309T140000Z
DTEND:20210309T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/21
DESCRIPTION:Title: Amenability of covers through critical exponents\nby Barbara
Schapira (Université de Rennes I) as part of Pangolin seminar\n\n\nAbstra
ct\nLet M be a negatively curved manifold. If M is “strongly positively
recurrent”\, i.e. there is a critical gap between its entropy at infinit
y and its entropy\, we show that a cover M' of M is amenable if and only i
f the critical exponents of M' and M coincide. The proof uses a constructi
on of Patterson-Sullivan measures twisted by a representation. This is a j
oint work with R. Dougall\, R. Coulon and S.Tapie.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Louis Merlin (Aachen University)
DTSTART:20210323T140000Z
DTEND:20210323T150000Z
DTSTAMP:20260404T110656Z
UID:Geometry/22
DESCRIPTION:Title: On the relations between the universal Teichmuller space and Anti
de Sitter geometry\nby Louis Merlin (Aachen University) as part of Pa
ngolin seminar\n\n\nAbstract\nAnti de Sitter (AdS) space is the Lorentzian
cousin of the hyperbolic 3-space: it is a symmetric space with constant c
urvature -1. In this talk\, we will consider surface group representations
in the isometry group of AdS space\, called quasi-Fuchsian representation
s. There is 2 classical objects associated to those representations and on
e of the goal is to understand their interplay: the limit set which is a q
uasi-circle in the boundary at infinity of AdS space and a convex set insi
de AdS which is preserved by the group action and bounded by two pleated s
urfaces. I will conclude the talk by a report on a work in common with Jea
n-marc Schlenker where we extend the "Teichmüller" situation to the "univ
ersal Teichmüller".\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leon Carvajales (Université de Paris-Sorbonne Université)
DTSTART:20210406T133000Z
DTEND:20210406T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/23
DESCRIPTION:Title: Growth of quadratic forms under Anosov subgroups\nby Leon Car
vajales (Université de Paris-Sorbonne Université) as part of Pangolin se
minar\n\n\nAbstract\nFor positive integers p and q we define a counting pr
oblem in the (pseudo-Riemannian symmetric) space of quadratic forms of sig
nature (p\,q) on R^{p+q}. This is done by associating to each quadratic fo
rm a geodesic copy of the Riemannian symmetric space of PSO(p\,q) inside t
he Riemannian symmetric space of PSL_{p+q}(R)\, and by looking at the orbi
t of this geodesic copy under the action of a discrete subgroup of PSL_{p+
q}(R). We then present some contributions to the study of this counting pr
oblem for Borel-Anosov subgroups of PSL_{p+q}(R).\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jean-Marc Schlenker (Université du Luxembourg)
DTSTART:20210420T133000Z
DTEND:20210420T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/24
DESCRIPTION:Title: The Weyl problem for unbounded convex surfaces in H^3\nby Jea
n-Marc Schlenker (Université du Luxembourg) as part of Pangolin seminar\n
\n\nAbstract\nThe classical Weyl problem in Euclidean space\, solved in th
e 1950s\, askswhether any smooth metric of positive curvature on the spher
e can be realized as the induced metric on the boundary of a unique convex
subset in $\\R^3$. It was extended by Alexandrov to the hyperbolic space\
, where a dual problem can also be considered: prescribing the third funda
mental form of a convex surface.\n\nWe will describe extensions of the Wey
l problem and its dual to unbounded convex surfaces in $H^3$. Two types of
generalizations can be stated\, one concerning unbounded convex surfaces\
, the other unbounded locally convex surfaces. Both questions have as spec
ial cases a number of known result or conjectures concerning 3-dimensional
hyperbolic geometry\, circle packings\, etc. We will present a rather gen
eral existence result concerning convex subsets.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matilde Martínez García (Universidad de la República\, Montevid
eo)
DTSTART:20210504T133000Z
DTEND:20210504T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/25
DESCRIPTION:Title: On tilings\, amenable equivalence relations and foliated spaces\nby Matilde Martínez García (Universidad de la República\, Montevide
o) as part of Pangolin seminar\n\n\nAbstract\nI will describe a family of
foliated spaces constructed from tylings on Lie groups. They provide a neg
ative answer to the following question by G.Hector: are leaves of a compac
t foliated space always quasi-isometric to Cayley graphs? Their constructi
on was motivated by a profound conjecture of Giordano\, Putnam and Skau on
the classification\, up to orbit equivalence\, of actions of countable am
enable groups on the Cantor set. I will briefly explain how these examples
relate to the GPS conjecture. This is joint work with Fernando Alcalde Cu
esta and Álvaro Lozano Rojo.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Barbara Nelli (Università dell’Aquila)
DTSTART:20210518T133000Z
DTEND:20210518T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/26
DESCRIPTION:Title: The topology of constant mean curvature surfaces with convex boun
dary\nby Barbara Nelli (Università dell’Aquila) as part of Pangolin
seminar\n\n\nAbstract\nWe discuss old and new results about the shape of
a constant mean curvature surfaces with strictly convex boundary\, contain
ed in the halfspace determined by the surface containing the boundary.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maria del Mar Gonzalez\, (Universidad Autónoma de Madrid)
DTSTART:20210601T133000Z
DTEND:20210601T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/27
DESCRIPTION:Title: Singular metrics of constant non-local curvature\nby Maria de
l Mar Gonzalez\, (Universidad Autónoma de Madrid) as part of Pangolin sem
inar\n\n\nAbstract\nWe will consider the problem of constructing singular
metrics of constant non-local curvature in conformal geometry\, using a gl
uing scheme. This non-local curvature is defined from the conformal fracti
onal Laplacian\, a Paneitz type operator of non-integer order. For the glu
ing process\, one needs a model solution which is given by the solution of
a non-local ODE with good conformal properties. It turns out that conform
al geometry provides powerful tools for the analysis of such equations.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Melanie Rupflin (Oxford University)
DTSTART:20210615T133000Z
DTEND:20210615T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/28
DESCRIPTION:Title: Lojasiewicz inequalities near simple bubble trees\nby Melanie
Rupflin (Oxford University) as part of Pangolin seminar\n\n\nAbstract\nIn
the study of (almost-)critical points of an energy functional one is ofte
n confronted with the problem that a weakly-obtained limiting object does
not have the same topology. For example sequences of almost-harmonic maps
from a surface will in general not converge to a single harmonic map but r
ather to a whole bubble tree of harmonic maps\, which cannot be viewed as
an object defined on the original domain.\n\nOne of the consequences of th
is phenomenon is that one of the most powerful tools in the study of (almo
st-)critical points and gradient flows of analytic functionals\, so called
Lojasiewicz-Simon inequalities\, no longer apply.\n\nIn this talk we disc
uss a method that allows us to prove such Lojasiewicz inequalities for the
harmonic map energy near simple trees and explain how these inequalities
allow us to prove convergence of solutions of the corresponding gradient f
low despite them forming a singularity at infinity.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Renato Vianna (Universidade Federal do Rio de Janeiro)
DTSTART:20210629T133000Z
DTEND:20210629T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/29
DESCRIPTION:Title: Sharp Ellipsoid Embeddings and Toric Mutations\nby Renato Via
nna (Universidade Federal do Rio de Janeiro) as part of Pangolin seminar\n
\n\nAbstract\nIn the study of (almost-)critical points of an energy functi
onal one is often confronted with the problem that a weakly-obtained limit
ing object does not have the same topology. For example sequences of almos
t-harmonic maps from a surface will in general not converge to a single ha
rmonic map but rather to a whole bubble tree of harmonic maps\, which cann
ot be viewed as an object defined on the original domain.\n\nOne of the co
nsequences of this phenomenon is that one of the most powerful tools in th
e study of (almost-)critical points and gradient flows of analytic functio
nals\, so called Lojasiewicz-Simon inequalities\, no longer apply.\n\nIn t
his talk we discuss a method that allows us to prove such Lojasiewicz ineq
ualities for the harmonic map energy near simple trees and explain how the
se inequalities allow us to prove convergence of solutions of the correspo
nding gradient flow despite them forming a singularity at infinity.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Misha Belolipetsky (IMPA\, Rio de Janeiro)
DTSTART:20210713T133000Z
DTEND:20210713T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/30
DESCRIPTION:by Misha Belolipetsky (IMPA\, Rio de Janeiro) as part of Pango
lin seminar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kathryn Mann (Cornell University)
DTSTART:20210921T133000Z
DTEND:20210921T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/31
DESCRIPTION:by Kathryn Mann (Cornell University) as part of Pangolin semin
ar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kathryn Mann (Cornell University)
DTSTART:20210928T133000Z
DTEND:20210928T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/32
DESCRIPTION:Title: How many Anosov flows can you put on a (closed\, hyperbolic) 3 ma
nifold?\nby Kathryn Mann (Cornell University) as part of Pangolin semi
nar\n\n\nAbstract\nThis question is one part of the puzzle connecting the
topology and geometry of a manifold to the possible dynamical systems that
it supports\, in this case the classification problem of Anosov flows.
I will motivate this question and describe some work with Jonathan Bowden
constructing flows on hyperbolic 3-manifolds\, as well as some recent join
t work on the classification problem joint with Thomas Barthelme and Steve
n Frankel.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Benoît Kloeckner (Université Paris-Est - Créteil Val-de-Marne)
DTSTART:20211012T133000Z
DTEND:20211012T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/33
DESCRIPTION:Title: Effective high-temperature estimates ensuring a spectral gap\
nby Benoît Kloeckner (Université Paris-Est - Créteil Val-de-Marne) as p
art of Pangolin seminar\n\n\nAbstract\nThe main goal of the talk shall be
to explain a few ideas from two classical theories : the thermodynamical f
ormalism\, and the perturbation of linear operators.\nThe "thermodynamical
formalism" is a framework to describe particular invariant measures of dy
namical systems\, called "equilibrium states"\, parametrized by functions
on the phase space\, called "potentials". This formalism is based on the "
transfer operator"\; when this operator has a spectral gap\, the equilibri
um state exists\, is unique\, and has very good statistical properties (ex
ponential mixing\, Central Limit Theorem\, etc.)\nIf one perturbs slightly
the potential\, the corresponding transfer operator is also perturbed.\nT
he classical theory of perturbation of operators ensures that the spectral
gap property is an open condition and that under bounded pertubration\, t
he eigendata of an operator depends analytically on the perturbation. It t
urns out that using the Implicit Function Theorem\, this theory can be mad
e effective with explicit bounds on the size of a neighborhood where the s
pectral gap persists.\nUsing this effective perturbation theory\, we show
completely explicit bound on the potential ensuring the spectral gap prope
rty for transfert operators of classical families of dynamical systems.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mohammad Ghomi (Georgia Institute of Technology)
DTSTART:20211026T133000Z
DTEND:20211026T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/34
DESCRIPTION:Title: Shortest closed curve to inspect a sphere\nby Mohammad Ghomi
(Georgia Institute of Technology) as part of Pangolin seminar\n\n\nAbstrac
t\nWe show that in Euclidean 3-space any closed curve which lies outside
the unit sphere and contains the sphere within its convex hull has length
at least 4Pi. Equality holds only when the curve is composed of 4 semicirc
les of length Pi\, arranged in the shape of a baseball seam\, as conjectur
ed by V. A. Zalgaller in 1996. This is joint work with James Wenk.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicolau Saldanha (Pontifícia Universidade Católica\, Rio de Jane
iro)
DTSTART:20211109T133000Z
DTEND:20211109T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/35
DESCRIPTION:Title: The homotopy type of spaces of locally convex curves in the spher
e\nby Nicolau Saldanha (Pontifícia Universidade Católica\, Rio de Ja
neiro) as part of Pangolin seminar\n\n\nAbstract\nA smooth curve $\\gamma:
[0\,1] \\to S^2$ is locally convex if its geodesic curvature is positive
at every point. J. A. Little showed that the space of all locally positive
curves $\\gamma$ with $\\gamma(0) = \\gamma(1) = e_1$ and $\\gamma'(0) =
\\gamma'(1) = e_2$ has three connected components. Our first aim is to des
cribe the homotopy type of these spaces. One of the connected components i
s known to be contractible. The two other connected components are homotop
ically equivalent to $(\\Omega S^3) \\vee S^2 \\vee S^6 \\vee S^{10} \\vee
\\cdots$ and $(\\Omega S^3) \\vee S^4 \\vee S^8 \\vee S^{12} \\vee \\cdot
s$\, respectively: we describe the equivalence.\n\nMore generally\, a smoo
th curve $\\gamma: [0\,1] \\to S^n$ is locally convex if \\[ \\det(\\gamma
(t)\, \\gamma'(t)\, \\ldots\, \\gamma^{(n)}(t)) > 0 \\] for all $t$. A mot
ivation for considering this space comes from linear ordinary differential
equations. Again\, we would like to know the homotopy type of the space o
f locally convex curves with prescribed initial and final jets. We present
several partial results.\n\nIncludes joint work with E. Alves\, V. Goular
t\, B. Shapiro\, M. Shapiro\, C. Zhou and P. Zuhlke\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marie-Amélie Lawn (Imperial College\, London)
DTSTART:20211123T133000Z
DTEND:20211123T143000Z
DTSTAMP:20260404T110656Z
UID:Geometry/36
DESCRIPTION:Title: Translating solitons of the mean curvature flow in cohomogeneity
one manifolds\nby Marie-Amélie Lawn (Imperial College\, London) as pa
rt of Pangolin seminar\n\n\nAbstract\nWe study new examples of translating
solitons of the mean curvature flow. We consider for this purpose manifol
ds admitting pseudo-Riemannian submersions and cohomogeneity one actions b
y isometries on suitable open subsets. This general setting also covers th
e well-known classical Euclidean examples of translating solitons invarian
t by some group actions. As an application\, we completely classify the ro
tationally invariant translating solitons in Minkowski space.\n
LOCATION:https://stable.researchseminars.org/talk/Geometry/36/
END:VEVENT
END:VCALENDAR