Geometry & Dynamics Seminar 2022-23

Some seminar talks will take place in Schreiber Building, room 309, and in addition

will be broadcasted via the zoom app, while other talks will run entirely via the zoom app.

The seminar will take place on Wednesdays at 14:10.

Please check each announcement since this is sometimes changed.

The zoom link is available upon request by email.


Upcoming Talks        Previous Talks        Previous Years

26.10.2022, 14:10 (Wednesday) Cheuk Yu Mak (University of Edinburgh)

Title: Some cute applications of Lagrangian cobordisms
Location: Zoom session

Abstract: In this talk, we will discuss, from a quantitative aspect, the following
symplectic questions: packing Lagrangian submanifolds, displacing Lagrangian
submanifolds, and constructing Lagrangian surfaces with a prescribed genus.
We will illustrate some interesting features of these questions using simple
examples. The focus will be put on explaining some new ideas from the point
of view of Lagrangian cobordisms. This is a joint work with Jeff Hicks.

02.11.2022, 17:10 (Wednesday)
Pierre-Alexandre Mailhot (University of Montreal)


Spectral diameter, Liouville domains and symplectic cohomology
Location: Zoom session

Abstract: The spectral norm provides a lower bound to the Hofer norm. It is thus
natural to ask whether the diameter of the spectral norm is finite or not.
In the case of closed symplectic manifolds, there is no unified answer.
For instance, for a certain class of symplecticaly aspherical manifolds,
which contains surfaces, the spectral diameter is infinite. However, for
CP^n, the spectral diameter is known to be finite. During this talk, I will
prove that, in the case of Liouville domains, the spectral diameter is
finite if and only if the symplectic cohomology of the underlying manifold
vanishes. With that relationship in hand, we will explore applications to
symplecticaly aspherical symplectic manifolds and give a new proof that the
spectral diameter is infinite on cotangent disk bundles.

09.11.2022, 14:10 (Wednesday) Grigory Mikhalkin (University of Geneva) - Blumenthal Lecture in Geometry

Title: Toric geometry and tropical trigonometry
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: Toric varieties were constructed as algebraic varieties about 50 years ago,
and also as symplectic varieties about 40 years ago. The two constructions
are dual to each other, but are based on the same geometry in R^n. Symmetries
in this geometry are linear transformations given by invertible n-by-n
matrices with integer coefficients, as well as all translations. This makes
the notion of a tangent integer vector as well as a notion of tropical curve
well-defined. The talk will review basic constructions with a focus on
tropical triangles that underlie some recent progress in symplectic embedding


10.11.2022, 16:15 (Thursday) Grigory Mikhalkin (University of Geneva) - Blumenthal Lecture in Geometry

Title: Tropical, real and symplectic geometry
Location: Orenstein bldg., room 111, Tel Aviv University (and online via zoom)

Abstract: This lecture will focus on the way how tropical curves appear in symplectic
geometry settings. On one hand, tropical curves can be lifted as Lagrangian
submanifolds in the ambient toric variety. On the other hand, they can be
lifted as holomorphic curves. The two lifts use two different tropical
structures on the same space, related by a certain potential function. We
pay special attention to correspondence theorems between tropical curves and
real curves, i.e. holomorphic curves invariant with respect to an
antiholomorphic involution. The resulting real curves produce, in their
turn, holomorphic membranes for tropical Lagrangian submanifolds.

16.11.2022, 14:10 (Wednesday)
Jinxin Xue (Tsinghua University)

Title: Dynamics of composite symplectic Dehn twists
Location: Zoom session (and screening in Schreiber bldg., room 309, Tel Aviv University)

Abstract: It is classically known in Nielson-Thurston theory that the mapping class
group of a hyperbolic surface is generated by Dehn twists and most elements
are pseudo Anosov. Pseudo Anosov elements are interesting dynamical objects.
They are featured by positive topological entropy and two invariant singular
foliations expanded or contracted by the dynamics. We explore a generalization
of these ideas to symplectic mapping class groups. With the symplectic Dehn
twists along Lagrangian spheres introduced by Arnold and Seidel, we show in
various settings that the  compositions of such twists has features of pseudo
Anosov elements, such as positive topological entropy, invariant stable and
unstable laminitions, exponential growth of Floer homology group, etc. This
is a joint work with Wenmin Gong and Zhijing Wang.

23.11.2022, 17:10 (Wednesday) Marcelo S. Atallah (University of Montreal)

Title: Fixed points of small Hamiltonian diffeomorphisms and the Flux conjectures
Location: Zoom session

Abstract: Inspired by the work of Lalonde-McDuff-Polterovich, we describe how the C^0
and C^1 flux conjectures relate to new instances of the strong Arnol’d
conjecture and make new progress on the C0 flux conjecture. This is joint
work in progress with Egor Shelukhin.

30.11.2022, 14:10 (Wednesday) Joé Brendel (Tel Aviv University)

Title: Pinwheels as Lagrangian barriers
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: Pinwheels are certain singular Lagrangians in four-dimensional
symplectic manifolds. In this talk we focus on the case of the complex
projective plane, where pinwheels arise naturally as visible Lagrangians
in its almost toric fibrations or, alternatively, as vanishing cycles of
its degenerations. Pinwheels have been shown to have interesting
rigidity properties by Evans--Smith. The goal of this talk is to show
that Lagrangian pinwheels are Lagrangian barriers in the sense of Biran,
meaning that their complement has strictly smaller Gromov width than the
ambient space. Furthermore, we will discuss a connection to the Lagrange
spectrum. This is joint work with Felix Schlenk.

07.12.2022, 14:10 (Wednesday) Yoel Groman (Hebrew University of Jerusalem)

Title: Closed string mirrors of symplectic cluster manifolds
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: Consider a symplectic Calabi Yau manifold equipped with a Maslow 0 Lagrangian
torus fibration with singularities. According to modern interpretations of
the SYZ conjecture, there should be an associated  analytic mirror variety
with a non Archimedean torus fibration over the same base. I will suggest a
general construction called the closed string mirror which is based on
relative symplectic cohomologies of the fibers. A priori the closed string
mirror is only a set with a map to the base, but conjecturally under some
general hypotheses it is in fact an analytic variety with its non Archimedean
torus fibration. I will discuss joint work with Umut Varolgunes where we prove
this in the case of four dimensional symplectic cluster manifolds.

14.12.2022, 14:10 (Wednesday) Mira Shamis (Queen Mary University of London)

Title: On the abominable properties of the Almost Mathieu operator with Liouville frequencies
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: We show that, for sufficiently well approximable frequencies, several
spectral characteristics of the Almost Mathieu operator can be as poor
as at all possible in the class of all discrete Schroedinger
operators. For example, the modulus of continuity of the integrated
density of states may be no better than logarithmic. Other
characteristics to be discussed are homogeneity, the Parreau-Widom
property, and (for the critical AMO) the Hausdorff content of the
spectrum. Based on joint work with A. Avila, Y. Last, and Q. Zhou.

21.12.2022, 14:10 (Wednesday) Maksim Stokic (Tel Aviv University)

Title: Flexibility of the adjoint action of the group of Hamiltonian diffeomorphisms
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: The space of Hamiltonian diffeomorphisms has a structure of an infinite
dimensional Frechet Lie group, with Lie algebra isomorphic to the space
of normalized functions and adjoint action given by pull-backs. We show
that this action is flexible: for a non-zero normalized function $f$,
any other normalized function can be written as a sum of differences of
elements in the orbit of $f$ generated by the adjoint action. Additionally,
the number of elements in this sum is dominated from above by the
$L_{\infty}$-norm of $f$. This result can be interpreted as an (bounded)
infinitesimal version of the Banyaga's result on simplicity of $Ham(M,\omega)$.
Moreover, it can be used to remove the $C^{\infty}$-continuity condition
in the Buhovsky-Ostrover theorem on the uniqueness of Hofer's metric.
This is joint work with Lev Buhovsky.

28.12.2022, 14:10 (Wednesday) Albert Fathi (Georgia Tech)

Title: Smooth Lyapunov functions on closed subsets and isolating neighbourhoods
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: We will discuss unified and simplified proofs of some previously known
theorems relating dynamics and Lyapunov functions. In particular, we
will give a proof of the existence of isolating blocks for isolated
invariant sets.

04.01.2023, 14:00-15:00 (Wednesday) Iosif Polterovich (University of Montreal)

Title: Pólya's eigenvalue conjecture: some recent advances
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: The celebrated Pólya’s conjecture (1954) in spectral geometry states that
the eigenvalue counting functions of the Dirichlet and Neumann Laplacian
on a bounded Euclidean domain can be estimated from above and below,
respectively, by the leading term of Weyl’s asymptotics. The conjecture
is known to be true for domains which tile the Euclidean space, however
it remains largely open in full generality. In the talk we will explain
the motivation behind this conjecture and discuss some recent advances,
notably, the proof of Pólya’s conjecture for the disk. The talk is based
on a joint work with Nikolay Filonov, Michael Levitin and David Sher.

04.01.2023, 15:20-16:20 (Wednesday) Shira Tanny (IAS Princeton)

Title: Closing lemmas in contact dynamics and holomorphic curves
Location: Schreiber bldg., room 209, Tel Aviv University (and online via zoom)

Abstract: Given a flow on a manifold, how to perturb it in order to create a periodic
orbit passing through a given region? While the first results in this
direction were obtained in the 1960-ies, various facets of this question
remain largely open. I will review recent advances on this problem in the
context of contact flows, which are closely related to Hamiltonian flows
from classical mechanics. In particular, I'll discuss a proof of a
conjecture of Irie stating that rotations of odd-dimensional ellipsoids
admit a surprisingly large class of perturbations creating periodic orbits.
The proof involves methods of modern symplectic topology including
pseudo-holomorphic curves and contact homology. The talk is based on a
joint work with Julian Chaidez, Ipsita Datta and Rohil Prasad, as well
as a work in progress joint with Julian Chaidez.

11.01.2023, 17:10 (Wednesday) Yuhan Sun (Rutgers University)

Title: Heavy sets and relative symplectic cohomology
Location: Zoom session

Abstract: Heavy sets were introduced by Entov-Polterovich around 2009. They reveal
suprising rigidity of certain compact subsets of a closed symplectic manifold,
from a functional persepective. When a compact subset is a smooth Lagrangian
submanifold, there is a well-established relation between its heaviness and
the non-vanishing of its Lagrangian Floer cohomology. In this talk we
describe an equivalence between the heaviness of general compact subsets
and the non-vanishing of another Floer-type invariant, called the relative
symplectic cohomology. If time permits, we will discuss applications and
questions we learned from this equivalence. Based on joint work with C.Mak
and U.Varolgunes.

18.01.2023, 14:10 (Wednesday)
Michael Entov (Technion)

Title: Kahler-type embeddings of balls into symplectic manifolds
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: A symplectic embedding of a disjoint union of balls into a symplectic
manifold M is called Kahler-type if it is holomorphic with respect
to some (not a priori fixed) complex structure on M compatible with
the symplectic form. Assume that M either of the following: CP^n (with
the standard symplectic form), an even-dimensional torus or a K3 surface
equipped with an irrational Kahler-type symplectic form. Then:

1. Any two Kahler-type embeddings of a disjoint union of balls into M
can be mapped into each other by a symplectomorphism acting trivially on
the homology. If the embeddings are holomorphic with respect to complex
structures compatible with the symplectic form and lying in the same
connected component of the space of Kahler-type complex structures on M,
then the symplectomorphism can be chosen to be smoothly isotopic to the

2. Symplectic volume is the only obstruction for the existence of
Kahler-type embeddings of k^n equal balls (for any k) into CP^n and of
any number of possibly different balls into a torus or a K3 surface.
This is a joint work with M.Verbitsky.

15.03.2023, 14:10 (Wednesday) Ely Kerman (University of Illinois Urbana-Champaign)

Title: Mean width, symplectic capacities and volume
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: In this talk, I will discuss an inequality between a symplectic version
of the mean width of a convex body and its symplectic capacity. This is
motivated by and generalizes an equality established by Artstein-Avidan
and Ostrover. The proof utilizes their symplectic Brunn-Minkowski
inequality together with a local version of Viterbo's conjecture
established by Abbondandolo and Benedetti. I will also describe several
examples and secondary results that suggest that the difference between
the symplectic mean width and the mean width is deeply related to toric
symmetry. This is joint work in progress with Jonghyeon Ahn.

22.03.2023, 14:10 (Wednesday) Laurent Charles (Sorbonne University, Paris)

Title: On magnetic Laplacian on compact surfaces
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: I will discuss the relations between magnetic geodesic flows
on closed manifolds and the corresponding quantum Hamiltonians. For
hyperbolic surfaces with constant magnetic field, the magnetic flow is
periodic up to some critical energy, and the corresponding eigenvalues
of the magnetic Laplacian have high degeneracies.
 More generally, in the semiclassical limit, magnetic Laplacians have
spectral clusters. In each cluster, the dynamic and the eigenvalue
distribution can be described in terms of Toeplitz operators.

29.03.2023, 14:10 (Wednesday) Pazit Haim-Kislev (Tel Aviv University)

Title: Symplectic Barriers
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: In his seminal 2001 paper, Biran introduced the concept of Lagrangian
Barriers, a symplectic rigidity phenomenon coming from obligatory
intersections with Lagrangian submanifolds which doesn't come from
mere topology. Since then several other examples for Lagrangian barriers
have been discovered. In this joint work with Richard Hind and Yaron
Ostrover, we introduce the first example (as far as we know) of Symplectic
Barriers, a symplectic rigidity coming from obligatory intersections of
symplectic embeddings with symplectic submanifolds (and in particular
not Lagrangian).

Special seminar:

18.04.2023, 16:10 (Tuesday) River Chiang (National Cheng Kung University)

Title: Examples of higher dimensional non-fillable contact manifolds
Location: Kaplun bldg., room 205, Tel Aviv University

Special seminar:

19.04.2023, 11:00 (Wednesday) Boris Khesin (University of Toronto)

Title: Geodesic framework for vortex sheets and generalized fluid flows
Location: Schreiber bldg., room 309, Tel Aviv University

Abstract: We discuss ramifications of Arnold’s group-theoretic approach to ideal
hydrodynamics as the geodesic flow for a right-invariant metric on the
group of volume-preserving diffeomorphisms. It turns out that many
equations of mathematical physics, such as the motion of vortex sheets
or fluids with moving boundary, have Lie groupoid, rather than Lie
group, symmetries.
We present their geodesic setting, which also allows one to describe
multiphase fluids, homogenized vortex sheets and Brenier’s generalized flows.
This is a joint work with Anton Izosimov.

19.04.2023, 14:10-15:00 (Wednesday) Viktor L. Ginzburg (University of California, Santa Cruz) - TIDY Distinguished Lecture

Title: Topological Entropy of Reeb Flows, Barcodes and Floer Theory
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: Topological entropy is one of the fundamental invariants of a dynamical
system, measuring its complexity. In this talk, we focus on connections
between the topological entropy of a Hamiltonian dynamical system, e.g.,
a Hamiltonian diffeomorphism or a Reeb or geodesic flow, and its
Symplectic/Floer homology. We recall the definition of barcode entropy —
a Floer theoretic counterpart of topological entropy — and discuss
possible ways to extend it to Reeb flows. The talk is based on joint
work with Erman Cineli, Basak Gurel and Marco Mazzucchelli.

19.04.2023, 15:10-16:00 (Wednesday) Başak Z. Gürel (University of Central Florida) - TIDY Distinguished Lecture

Title: On the volume of Lagrangian submanifolds
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: We will discuss the continuity property of the surface area of Lagrangian
submanifolds, or to be more precise its lower semi-continuity with respect
to the gamma-norm, and connections with integral geometry, Floer theory
and barcodes. The talk is based on joint work with Erman Cineli and
Viktor Ginzburg.

Special joint G&D and RCG seminar:

27.04.2023, 16:15 (Thursday) Igor Zelenko (Texas A&M University)

Title: Gromov's h-principle for corank two distribution of odd rank with maximal first Kronecker index
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: Many natural geometric structures on manifolds are given as sections of
certain bundles satisfying open relations at every point, depending on
the derivatives of these sections. Such relations are called open
differential relations. Symplectic, contact, and even contact structures
on manifolds can be described in this way. The natural question is: do
structures satisfying given open relations (called the genuine solutions
of the differential relation) exist on a given manifold? Replacing all
derivatives appearing in a differential relation by the additional
independent variables, one obtains an open subset of the corresponding
jet bundle. A formal solution of the differential relation is a section
of the jet bundle lying in this open set. The existence of a formal
solution is obviously a necessary condition for the existence of the
genuine one. One says that a differential relation satisfies a
(nonparametric) h-principle if any formal solution is homotopic to
the genuine solution in the space of formal solutions.

Versions of the h-principle have been successfully established for
corank 1 distributions satisfying natural open relations. Such results
are among the most remarkable advances in  differential topology in the
last four decades. However, very little is known about analogous results
for other classes of distributions, e.g. generic distributions of corank 2
or higher (except the so-called Engel distributions, the smallest
dimensional case of maximally  nonholonomic distributions of corank 2
distributions on 4-dimensional manifolds).

In my talk, I will show how to use the method of convex integration in
order to establish all versions of the h-principle for corank 2
distributions of arbitrary odd rank satisfying a natural generic
assumption on the associated pencil of skew-symmetric forms. During
the talk, I will try to give all the necessary background. This is the
joint work with Milan Jovanovic, Javier Martinez-Aguinaga, and
Alvaro del Pino.

TAU Math Colloquium:

01.05.2023, 12:15 (Monday) Shmuel Weinberger (University of Chicago) - TIDY Distinguished Lecture 1/2

Title: Finite group actions on aspherical spaces
Location: Schreiber bldg., room 006, Tel Aviv University

Abstract: I will start by explaining why any finite simplicial
complex is the fixed set of a simplicial action of a group of order
120 on some high dimensional disk. (This is based on work from the
1970s of Jones, Oliver, Assadi and others).  The analogous question
for the product of a circle and a disk is much more difficult.  I will
discuss this latter problem (following joint work with Cappell and
Yan) and try to explain how traces in algebraic K-theory (no knowledge
of this topic assumed) enter in this and a much wider class of

This is the first talk of the 2023 TIDY lecture series titled
Some geometry associated to torsion in discrete groups

03.05.2023, 14:10 (Wednesday) Shmuel Weinberger (University of Chicago) - TIDY Distinguished Lecture 2/2

Title: Torsion, L^2 cohomology and complexity
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: This talk is a hermitian analog of the previous one, but is
completely independent of it in terms of its actual content.

Atiyah introduced real valued L^2 betti numbers as a way of
understanding the (usually infinite dimensional) cohomology of
universal covers of finite complexes.  As far as anyone knows these
are always integers for torsion free fundamental group, but for groups
with torsion very much more exotic possibilities arise.

We will use this and an invariant of Cheeger and Gromov to see that
whenever an oriented smooth manifold of dimension 4k+3 has torsion in
its fundamental group, there are many other manifolds homotopy
equivalent but not diffeomorphic to it and that in the known
situations where betti numbers can be irrational there is even an
infinitely generated group of such!  And, I will also use this
invariant to explain how many simplices (roughly) it takes to build a
standard Lens space.  This is based on old work with Stanley Chang,
and recent work with Geunho Lim.

This is the second talk of the 2023 TIDY lecture series titled
Some geometry associated to torsion in discrete groups

10.05.2023, 14:10-15:00 (Wednesday) Gleb Smirnov (University of Geneva)

Title: Lagrangian rigidity in K3 surfaces
Location: Zoom session (and screening in Schreiber bldg., room 309, Tel Aviv University)

Abstract: Sheridan-Smith and Entov-Verbitsky show that every Maslov-zero Lagrangian
torus in a K3 surface has a nontrivial and primitive homology class.
In this talk, we prove the "nontrivial" part of their theorem with a
different method and the converse result.

10.05.2023, 15:10-16:00 (Wednesday) Marcelo R. R. Alves (University of Antwerp)

Title: C^0-stability of topological entropy for 3-dimensional Reeb flows
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: The C^0-distance on the space of contact forms on a contact manifold has
been studied recently by different authors. It can be thought of as an
analogue for Reeb flows of the Hofer metric on the space of Hamiltonian
diffeomorphisms. In this talk, I will explain some recent progress on
the stability properties of the topological entropy with respect to this
distance. This is joint work with Lucas Dahinden, Matthias Meiwes and
Abror Pirnapasov.

17.05.2023, 14:10 (Wednesday) Joé Brendel (Tel Aviv University)

Title: Lagrangian product tori in $S^2 \times S^2$
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: A Lagrangian product torus in $S^2 \times S^2$ is a Lagrangian
torus obtained by taking a product of circles. The main goal of this
talk is to give a symplectic classification of product tori and
illustrate that interesting things can happen in case the symplectic
form is non-monotone. We make a detour through toric geometry and
discuss the more general classification question of toric fibres. If
time permits, we will discuss related questions and some applications.
This is partially based on joint work with Joontae Kim.

24.05.2023, 14:10 (Wednesday) Ilia Gaiur (University of Toronto, Weizmann Institute of Science)

Title: Normal forms in the truncated gl_n Lie algebras
Location: Schreiber bldg., room 309, Tel Aviv University

Abstract: Fix a finite dimensional Lie algebra $\mathfrak{g}$. The truncated loop
algebra of $\mathfrak{g}$ is a finite dimensional Lie algebra which
may be seen as the algebra of r-jets of maps from $\mathbb{C}^*$ to
$\mathfrak{g}$. Such algebras are examples of finite dimensional
non-semisimple Lie algebras which, however, allow a nice description.
I will give a review of the Lie-Poisson theory for such algebras and
will explain in detail the geometry of the co-adjoint orbits of such
algebras corresponding to $\mathfrak{gl}_n$. I will introduce the
notion of a normal form for such Lie algebras and discuss degenerations
of their co-adjoint orbits. At the end of the talk I will give a brief
review of how different types of geometries appear in the study of
integrable systems and moduli spaces of differential equations.

31.05.2023, 14:10 (Wednesday) Lenya Ryzhik (Nirit and Michael Shaoul Fellow, Stanford University)

Title: Diffusion of learning models
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: The notion of diffusion of knowledge goes at least as far back to
Chapter 1 of the "Pickwick Papers". However, its mathematical modeling
in macroeconomics is much more recent. We will discuss some models
proposed by R. Lucas and B. Moll about ten years ago.
Various versions lead to the mean field games type PDE and also
infinite-dimensional optimal control Hamilton-Jacobi problems. We will
discuss the little mathematical progress but mostly focus on the
modeling and open questions aspects.

07.06.2023, 14:10 (Wednesday) Hyunmoon Kim (University of Toronto, Tel Aviv University)

Title: The real orbits of complex Lagrangian Grassmannians
Location: Schreiber bldg., room 309, Tel Aviv University (and online via zoom)

Abstract: The Riemann sphere can be broken up into three orbits of SL(2, R), as
two open hemispheres and a great circle. We will discuss a generalization
of this phenomenon in complex Lagrangian Grassmannians of higher
dimensions under the action of the real symplectic group. We will
give formulas for the number of orbits, incidence relations, and
their dimensions. We will also show homotopy equivalences between
these orbits and some other Grassmannian objects, and if time permits,
a strategy to compute their homology.

14.06.2023, 14:10 (Wednesday) Lev Birbrair (The Federal University of Ceará and Jagiellonian University)

Title: Outer Lipschitz Geometry of germs of Semialgebraic (Definable) surfaces
Location: Zoom session (and screening in Schreiber bldg., room 309, Tel Aviv University)

Abstract: I am going to describe the first attempt of outer Lipschitz Classification
of germs of Semialgebraic Surfaces. We show how the classification
question can be solved for a special case - the surfaces, obtained as
a union of two Normally Embedded Hölder triangles.

21.06.2023, 14:10 (Wednesday) Stefan Nemirovski (Steklov Mathematical Institute and Ruhr University Bochum)

Title: Legendrian links and déjà vu moments
Location: Zoom session (and screening in Schreiber bldg., room 309, Tel Aviv University)

Abstract: Legendrian links in the space of null geodesics of a spacetime
can be used to detect "déjà vu moments", i.e. different instances
at which an observer receives the same light ray. In the talk,
I'll discuss the relevant class of Legendrian links and some
ensuing open problems.

Organized by Misha Bialy, Lev Buhovsky, Yaron Ostrover, and Leonid Polterovich