School of Mathematics

The min-max width of unit volume three-spheres

Lucas Ambrozio
University of Warwick; Member, School of Mathematics
November 20, 2018
The (Simon-Smith) min-max width of a Riemannian three dimensional sphere is a geometric invariant that measures the tightest way, in terms of area, of sweeping out the three-sphere by two-spheres. In this talk, we will explore the properties of this geometric invariant as a functional on the space of unit volume

This is joint work with Rafael Montezuma.

Almgren's isomorphism theorem and parametric isoperimetric inequalities

Yevgeny Liokumovich
Massachusetts Institute of Technology; Member, School of Mathematics
November 20, 2018
In the 60's Almgren initiated a program for developing Morse theory on the space of flat cycles. I will discuss some simplifications, generalizations and quantitative versions of Almgren's results about the topology of the space of flat cycles and their applications to minimal surfaces.

I will talk about joint works with F. C. Marques and A. Neves, and L. Guth.

Introduction to Query-to-Communication Lifting

Mika Goos
Member, School of Mathematics
November 20, 2018
I will survey new lower-bound methods in communication complexity that "lift" lower bounds from decision tree complexity. These methods have recently enabled progress on core questions in communication complexity (log-rank conjecture, classical--quantum separations) and related areas (circuit complexity, proof complexity, LP/SDP formulations). I will prove one concrete lifting theorem for non-deterministic (NP) query/communication models.

Lyapunov exponents for small random perturbations of predominantly hyperbolic two dimensional volume-preserving diffeomorphisms, including the Standard Map

Alex Blumenthal
University of Maryland
November 19, 2018
An outstanding problem in smooth ergodic theory is the estimation from below of Lyapunov exponents for maps which exhibit hyperbolicity on a large but non- invariant subset of phase space. It is notoriously difficult to show that Lypaunov exponents actually reflect the predominant hyperbolicity in the system, due to cancellations caused by the“switching” of stable and unstable directions in those parts of phase space where hyperbolicity is violated.

A tale of two conjectures: from Mahler to Viterbo.

Yaron Ostrover
Tel Aviv University; von Neumann Fellow, School of Mathematics
November 19, 2018
In this talk we explain how billiard dynamics can be used to relate a symplectic isoperimetric-type conjecture by Viterbo with an 80-years old open conjecture by Mahler regarding the volume product of convex bodies. The talk is based on a joint work with Shiri Artstein-Avidan and Roman Karasev.

Morse-Theoretic Aspects of the Willmore Energy

Alexis Michelat
ETH Zurich
November 13, 2018
We will present the project of using the Willmore elastic energy as a quasi-Morse function to explore
the topology of immersions of the 2-sphere into Euclidean spaces and explain how this relates to the
classical theory of complete minimal surfaces with finite total curvature.

This is partially a joint work in collaboration with Tristan Rivière.

Translators for Mean Curvature Flow

David Hoffman
Stanford University
November 13, 2018
A translator for mean curvature flow is a hypersurface $M$ with the property that translation is a mean curvature flow. That is, if the translation is
$t\rightarrow M+t\vec{v}$, then the normal component of the velocity vector $\vec{v}$ is equal to the mean curvature $\vec{ H}$. I will discuss recent joint work with Tom Ilmanen, Francisco Martin and Brian White, specifically our classification of the the complete translators in $R^3$ that are graphical, and the construction of new families of complete translators that are not graphical.

Distinguishing fillings via dynamics of Fukaya categories

Yusuf Baris Kartal
Massachusetts Institute of Technology
November 12, 2018
Given a Weinstein domain $M$ and a compactly supported, exact symplectomorphism $\phi$, one can construct the open symplectic mapping torus $T_\phi$. Its contact boundary is independent of $\phi$ and thus $T_\phi$ gives a Weinstein filling of $T_0\times M$, where $T_0$ is the punctured 2-torus. In this talk, we will outline a method to distinguish $T_\phi$ from $T_0\times M$ using dynamics and deformation theory of their wrapped Fukaya categories.