2018
Jan
30

# Events & Seminars

2018
Jan
30

2018
Jan
30

2018
Jan
30

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

The Birch and Swinnerton-Dyer conjecture predicts that the group of rational points on an elliptic curve E over Q has rank equal to the order of vanishing of the L-function of E. Generalisations of this conjecture to motives M were formulated by Belinson and Bloch-Kato. I will explain a proof of a version of the Bloch-Kato conjecture in p-adic coefficients, when M is attached to a p-ordinary Hilbert modular form of any weight and the order of vanishing is 1.

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.

2017
Mar
02

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

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

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)

(All day)

## Location:

IIAS, Feldman Building, Givat Ram

10:00 - 11:00 Gilles Zemor. Background on quantum computing and coding.

11:30 - 12:30 Gilles Zemor. Quantum stabilizer codes and quantum LDPC codes.

14:00 - 15:00. Dorit Aharonov. Quantum locally testable codes.

15:15 - 16:15. Gilles Zemor. Quantum LDPC codes and high-dimensional expanders.

2018
Jan
21

2017
Jan
19

2017
Jan
05

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

לאירוע הזה יש שיחת וידאו.

הצטרף: https://meet.google.com/mcs-bwxr-iza

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

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