Seminars Sorted by Series

In [MIP*=RE by JNVWY] the authors construct a non-local game that resolves Tsirelson's problem to the negative and by that refute Connes' embedding conjecture (CEC). The game *-algebra (see e.g. [KPS]) enables one to construct a finitely presented *...

We study stability problems with respect to families of groups equipped with bi-invariant ultrametrics, that is, metrics satisfying the strong triangle inequality. This property has very strong consequences, and this form of stability behaves very...

We discuss various (still open) questions on approximations of finitely generated groups, focusing on finite-dimensional approximations such as residual finiteness and soficity. We survey our results on the existence, stability and quantification of...

In 1966 V. Arnold showed how solutions of the Euler equations of hydrodynamics can be viewed as geodesics in the group of volume-preserving diffeomorphisms. This provided a motivation to study the geometry of this group equipped with the $L^2$...

There are indications that in the 80s Guillemin posed a question: If billiard maps are conjugate, can we say that domains are the same up to isometry? On one side, we show that conjugacy of different domains can't be C^1 near the boundary. In...

We present a Hamiltonian framework for higher-dimensional vortex filaments (or membranes) and vortex sheets as singular 2-forms with support of codimensions 2 and 1, respectively, i.e. singular elements of the dual to the Lie algebra of divergence...

We review some recent developments in KAM theory. By exploiting some identities of a geometric nature, one can obtain iterative steps which lead to numerical algorithms and which can follow the tori till breakdown. We present theoretical results in...

I will discuss a middle-dimensional generalization of Gromov's Non-Squeezing Theorem.

We study particular solutions of the "inner equation" associated to the splitting of separatrices on "generalized standard maps". An exponentially small complete expression for their difference is obtained. We also provide numerical evidence that...

This is a series of 3 talks on the topology of Stein manifolds, based on work of Eliashberg since the early 1990ies. More specifically, I wish to explain to what extent Stein structures are flexible, i.e. obey an h-principle. After providing some...

In 1964 Arnold constructed an example of instabilities for nearly integrable systems and conjectured that generically this phenomenon takes place. There has been big progress attacking this conjecture in the past decade. Jointly with Ke Zhang we...

In 1964 Arnold constructed an example of instabilities for nearly integrable systems and conjectured that generically this phenomenon takes place. There has been big progress attacking this conjecture in the past decade. Jointly with Ke Zhang we...

We shall discuss billiard dynamics in convex billiard tables in R^n.

In particular, we will describe a "symplectic point of view" which can be used, for example, to study the length of the shortest periodic billiard trajectory.

We shall discuss some basic results on surface diffeomorphisms. Then we introduce some results which were studied by both symplectic method and dynamical method. Finally we introduce some related questions.

Through geometrical models, perturbation techniques and sometimes analytical approaches, it has been possible to establish a dictionary between "a taxonomy of generic dynamical phenomenons" and a list of "simple mechanisms or dynamical...

I will talk about Ginzburg and Gurel's work on Hamiltonian pseudo-rotations of projective spaces, in particular, their proof of no fixed point of a pseudo-rotation of projective space is isolated as an invariant set.

This is a survey talk. The goal is to describe recent developments in Celestial Mechanics obtained with techniques from Symplectic Dynamics, and discuss open problems. Emphasis will be given to the construction of transverse foliations and their...

In this survey talk I will describe developments in the study of the planar circular restricted 3-body problem that were made possible through the use of pseudo holomorphic curves, following the theory developed by Hofer, Wysocki and Zehnder.

We will discuss several examples where ideas from persistent homology have applications to the study of the coarse geometry of groups of Hamiltonian diffeomorphisms, equipped with the Hofer norm..

The key idea is to consider Hamiltonian Floer...

I will talk about Ginzburg and Gurel's work on Hamiltonian pseudo-rotations of projective spaces, in particular, their proof of no fixed point of a pseudo-rotation of projective space is isolated as an invariant set.

I would like to discuss three topics concerning applications of holomorphic curve methods to the planar circular restricted three-body problem. The first is the existence of direct orbits and a conjecture due to Birkhoff. The second is the use of...

I will show that a closed, negatively curved Riemannian manifold of 1/4 pinched negative curvature has constant negative curvature if and only if the Lyapunov spectrum of its geodesic flow is the same as that of a hyperbolic manifold. The Lyapunov...

One of the most useful tools in quantifying the complexityof a dynamical system are the concepts of topological and metricentropy. While relevant in several contexts, entropy plays aparticularly important role in describing the behaviour of...

We consider the elliptic restricted three-body problem as a perturbation of the circular problem, with the perturbation parameter being the eccentricity of the orbits of the primaries. We show that for every suitably small, non-zero perturbation...

I will discuss some technical details regarding properties of feral pseuodoholomorphic curves, specifically those properties arising from stretching constructions and as components of limit buildings arising from attempts to compactify certain...

Semitoric systems are a type of 4-dimensional integrable system which has been classified by Pelayo-Vu Ngoc in terms of five invariants, one of which is a family of polygons generalizing the Delzant polygons which classify 4-dimensional toric...

A symplectic Lie groupoid is a Lie groupoid with a multiplicative symplectic form. We take the perspective that such an object is symplectic manifold with an extra categorical structure. Applying the machinery of Floer theory, the extra structure is...