BEN GURION UNIVERSITY A C T I O N N O W Dear all, The next Action Now meeting will be held in Ben Gurion University on Wednesday 6.4. Speakers are Hugo Duminil-Copin, Kathryn Lindsey, Yaron Ostrover and Eitan Sayag. A detailed schedule will be available soon at <http://www.math.bgu.ac.il/~barakw/action> (I also pasted in the schedule below, M.C.) Coffee and local pastries will be served, so don't miss out! If you are arriving by car and need an entry permit to the campus, please send an email <to barakw@math.bgu.ac.il> ================= Schedule ============================== ACTION NOW WANDERING SEMINAR Fourth meeting, Ben Gurion University, 6.4.11 Building 58 (mathematics), seminar room -101 # 9:30 Gathering, coffee and authentic local pastries # 9:50 Hugo Duminil-Copin (Geneva) Conformal invariance in lattice models The aim of this talk is to provide an introduction to the study of lattice models at criticality. Through the examples of the self-avoiding walk and percolation, we will present the different questions that can be asked on these models. In this two-dimensional case, physicists predict that the so-called scaling limit of these models is conformally invariant. This information allows to describe precisely the critical regime. Recent developments due to Schramm, Smirnov and others allow to understand mathematically these predictions. We will review several of these results and present open questions. The talk will not require any background. # 11:10 Eitan Sayag (Ben Gurion University) TBA # 12:00 lunch! # 14:00 Kathryn Lindsey (Cornell) Counting minimal components of translation surfaces A holomorphic 1-form on a compact, complex curve C defines a flat metric and vector field on the complement of a finite set of points in C. Vertical flow with respect to this metric decomposes the surface into finitely many invariant subsets (components), which are either periodic or minimal. Yoav Naveh found tight upper bounds on the number of minimal and periodic components such a surface may have, with the bound being taken over all surfaces in any stratum of the moduli space of translation surfaces. Each stratum of the moduli space of translation surfaces consists of at most three connected components. Building on Naveh's work, I will present tight upper bounds on the number of minimal and periodic components for each connected component of this moduli space. # 15:00 Yaron Ostrover (Tel Aviv University) Hofer's metric on the group of Hamiltonian diffeomorphisms One of the most remarkable facts regarding the group of Hamiltonian diffeomorphisms is that it carries an intrinsic geometry given by a Finsler bi-invariant metric. This metric, which was discovered by Hofer in 1990, yields a geometric intuition for Hamiltonian systems, and it can be used in many ways as a powerful tool in symplectic geometry and dynamics. In this talk we will concentrate on the following question: are there other Finsler-type bi-invariant metrics on the group of Hamiltonian diffeomorphisms which are not equivalent to Hofer's metric? Or in other words: whether Hofer's metric is unique. The talk is intended for a general audience. You are cordially invited. --------------------------------------------------------- Technion Math Net-2 (TECHMATH2) Editor: Michael Cwikel <techm@math.technion.ac.il> Announcement from: Uri Bader <uri.bader@gmail.com>