2018 Jan 30

# Action Now Seminar: Oren Becker (HUJI), "Stability and Invariant Random Subgroups"

11:30am to 12:30pm

## Location:

IIAS, HUJI, Feldman Building, Room 130
2018 Apr 12

# Colloquium: Ron Peretz (Bar Ilan) - "Repeated Games with Bounded Memory - the Entropy Method"

2:30pm to 3:30pm

## Location:

Manchester Building (Hall 2), Hebrew University Jerusalem
2018 Jan 21

# NT&AG: Daniel Disegni (University of Paris-Sud 11), On the p-adic Bloch-Kato conjecture for Hilbert modular forms

3:00pm to 4:00pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel
2017 Mar 02

# Group actions seminar: David El-Chai Ben Ezra (HUJI) - The congruence subgroup problem for automorphism groups of  free meta-abelian groups

10:30am to 11:30am

2017 Nov 02

# Group actions: Remi Coulon (Rennes) - Growth gap in hyperbolic groups and amenability

10:30am to 11:30am

## Location:

hyperbolic groups and amenability
(joint work with Françoise Dal'Bo and Andrea Sambusetti) Given a finitely generated group G acting properly on a metric space X, the exponential growth rate of G with respect to X measures "how big" the orbits of G are. If H is a subgroup of G, its exponential growth rate is bounded above by the one of G. In this work we are interested in the following question: what can we say if H and G have the same exponential growth rate? This problem has both a combinatorial and a geometric origin. For the combinatorial part, Grigorchuck and Cohen
2017 Apr 27

# Group actions: Yair Glasner (BGU) - On Highly transitive permutation representations of groups.

10:30am to 11:30am

## Location:

Ross 70
Abstract: A permutation representation of a group G is called highly transitive if it is transitive on k-tuples of points for every k. Until just a few years ago groups admitting such permutation representations were thought of as rare. I will focus on three rather recent papers: G-Garion, Hall-Osin, Gelander-G-Meiri (in preparation) showing that such groups are in fact very common.
2018 May 10

# Groups & dynamics: Sanghoon Kwon (Kwandong University) - A combinatorial approach to the Littlewood conjecture in positive characteristic

10:30am to 11:30am

## Location:

Ross 70
The Littlewood conjecture is an open problem in simultaneous Diophantine approximation of two real numbers. Similar problem in a field K of formal series over finite fields is also still open. This positive characteristic version of problem is equivalent to whether there is a certain bounded orbit of diagonal semigroup action on Bruhat-Tits building of PGL(3,K).
2018 Feb 19

# HD-Combinatorics Special Day: Error correcting codes and high dim complexes (organised by Gilles Zemor)

10:00am to 4:15pm

## Location:

IIAS, Feldman Building, Givat Ram
2018 Jan 21

# Game Theory & Math Economics: Benny Moldovanu, University of Bonn "A Theory of Actions with Endogenous Valuations" (joint work with Alex Gershkov and Philipp Strack)

4:00pm to 5:00pm

## Location:

Elath Hall, 2nd floor, Feldman Building, Edmond Safra Campus
2017 Jan 19

# Groups and dynamics: Manfred Einsiedler (ETH) - Measure Rigidy and Quantitative Recurrence

10:30am to 11:30am

Ross 70
2017 Jan 05

# Groups and dynamics: Masaki Tsukamoto (lecture 5)

10:30am to 11:30am

Ross 70
2017 Nov 28

# T&G: Benjamin Ackermann (Hebrew University), Kodaira's embedding theorem

12:00pm to 1:30pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel
In this talk we present a proof of the Kodaira's theorem that gives a sufficient condition on the existence of an embedding of a Kahler manifold into CPn. This proof is based on the Kodaira Vanishing theorem, using a sheaf-cohomological translation of the embedding conditions. לאירוע הזה יש שיחת וידאו. הצטרף: https://meet.google.com/mcs-bwxr-iza
2015 Nov 09

# Number theory: Ishai Dan-Cohen (Essen), "Towards Chabauty-Kim loci for the polylogarithmic quotient over an arbitrary number field"

4:00pm to 5:45pm

## Location:

Ross Building, room 70, Jerusalem, Israel
Title: Towards Chabauty-Kim loci for the polylogarithmic quotient over an arbitrary number field Abstract: Let K be a number field and let S be an open subscheme of Spec O_K. Minhyong Kim has developed a method for bounding the set of S-valued points on a hyperbolic curve X over S; his method opens a new avenue in the quest for an "effective Mordell conjecture". But although Kim's approach has lead to the construction of explicit bounds in special cases, the problem of realizing the potential effectivity of his methods remains a difficult and beautiful open problem.
2015 Dec 07

# Number theory: Jean-Baptiste Teyssier (HUJI) "Kedlaya-Mochizuki theorem and applications"

4:00pm to 5:15pm

## Location:

Ross Building, room 70A
Let X be a complex manifold and let M be a meromorphic connection on X with poles along a normal crossing divisor D. Levelt-Turrittin theorem asserts that the pull-back of M to the formal neighbourhood of a codimension 1 point in D decom poses (after ramification) into elementary factors easy to work with. This decomposition may not hold at some other points of D. When it does, we say that M has good formal decomposition along D. A conjecture of Sabbah, recently proved by Kedlaya and Mochizuki independently, asserts roughly the
2017 Dec 19

# T&G: Yakov Eliashberg (Stanford), Simplifying singularities of Lagrangian skeleta

1:00pm to 2:30pm

## Location:

Room 63, Ross Building, Jerusalem, Israel
I will discuss in the talk David Nadler’s “arborealizaton conjecture” and will sketch its proof. The conjecture states that singularities of a Lagrangian skeleton of a symplectic Weinstein manifold could be always simplified to a finite list of singularities, called arboreal”. This is a joint work with Daniel Albarez-Gavela, David Nadler and Laura Starkston.