2019
Jun
19

# Events & Seminars

2019
Mar
18

# Special course: A. Goncharov (Yale, visiting Einstein Institute of Mathematics) "Quantum geometry of moduli spaces of local systems on surfaces and representation theory"

Repeats every week every Monday until Mon Apr 29 2019 except Mon Apr 22 2019.

4:00pm to 6:00pm4:00pm to 6:00pm

4:00pm to 6:00pm

4:00pm to 6:00pm

4:00pm to 6:00pm

4:00pm to 6:00pm

## Location:

Ross 70

Abstract. This is a joint work with Linhui Shen.
A decorated surface is an oriented surface with punctures and a finite collection of special points on the boundary, considered modulo isotopy.
Let G be a split adjoint group. We introduce a moduli space Loc(G,S) of G-local systems on a decorated surface S, which reduces to the character variety when S has no boundary, and quantize it.

2019
Mar
18

# NT & AG Lunch: Ehud DeShalit "An overview of class field theory"

1:00pm to 2:00pm

## Location:

Faculty lounge, Math building

Class field theory classifies abelian extensions of local and global fields
in terms of groups constructed from the base. We shall survey the main results of class
field theory for number fields and function fields alike. The goal of these introductory lectures
is to prepare the ground for the study of explicit class field theory in the function field case,
via Drinfeld modules.
I will talk for the first 2 or 3 times.

2019
Apr
02

2019
Mar
18

# NT & AG - Antoine Ducros (Sorbonne Université), "Non-standard analysis and non-archimedean geometry"

2:30pm to 3:30pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel

There is a general slogan according to which the limit behaviour of a one-parameter family of complex algebraic varieties when the parameter t tends to zero should be (partially) encoded in the associated t-adic analytic space in the sense of Berkovich; this slogan has given rise to deep and fascinating conjecturs by Konsevich and Soibelman, as well as positive results by various authors (Berkovich, Nicaise, Boucksom, Jonsson...).

2019
Mar
13

2019
May
15

# Set Theory Seminar - Gabriel Fernandes (BIU): Local core models with more Woodin cardinals

2:00pm to 3:30pm

## Location:

Ross 63

Abstract: We combine a technique of Steel with one due to Jensen and Steel to
obtain a core model below singular cardinals kappa which are
sufficiently closed under the beth function, assuming that there is no
premouse of height kappa with unboundedly many Woodin cardinals.
The motivation for isolating such core model is computing a lower bound for the strength of
the theory: T = ''ZFC + there is a singular cardinal kappa such that the set of ordinals below kappa where GCH holds is stationary and co-stationary''.

2019
May
22

# Set Theory Seminar - Gabriel Fernandes (BIU) (part II)

2:00pm to 3:30pm

## Location:

Ross 63

Abstract: We combine a technique of Steel with one due to Jensen and Steel to
obtain a core model below singular cardinals kappa which are
sufficiently closed under the beth function, assuming that there is no
premouse of height kappa with unboundedly many Woodin cardinals.
The motivation for isolating such core model is computing a lower bound for the strength of
the theory: T = ''ZFC + there is a singular cardinal kappa such that the set of ordinals below kappa where GCH holds is stationary and co-stationary''.

2019
Mar
12

# T&G: John Pardon (Princeton), Structural results in wrapped Floer theory

1:00pm to 2:30pm

## Location:

Room 110, Manchester Building, Jerusalem, Israel

I will discuss results relating different partially wrapped Fukaya categories. These include a K\"unneth formula, a `stop removal' result relating partially wrapped Fukaya categories relative to different stops, and a gluing formula for wrapped Fukaya categories. The techniques also lead to generation results for Weinstein manifolds and for Lefschetz fibrations. The methods are mainly geometric, and the key underlying Floer theoretic fact is an exact triangle in the Fukaya category associated to Lagrangian surgery along a short Reeb chord at infinity.

2019
Apr
08

# Combinatorics: Kim Minki (Technion) "The fractional Helly properties for families of non-empty sets"

11:00am to 1:00pm

## Location:

CS B-500, Safra campus

Speaker: Kim Minki, Technion
Title: The fractional Helly properties for families of non-empty sets
Abstract:
Let $F$ be a (possibly infinite) family of non-empty sets.
The Helly number of $F$ is defined as the greatest integer $m = h(F)$ for which there exists a finite subfamily $F'$ of cardinality $m$ such that every proper subfamily of $F'$ is intersecing and $F'$ itself is not intersecting.
For example, Helly's theorem asserts that the family of all convex sets in $d$-dimensional Euclidean space has Helly number $d+1$.

2019
Mar
25

# Combinatorics: Roy Meshulam (Technion) "Topology and combinatorics of the complex of flags"

11:00am to 1:00pm

## Location:

CS B-500, Safra campus

Speaker: Roy Meshulam (Technion)
Title: Topology and combinatorics of the complex of flags
Abstract:

2019
May
20

2019
Apr
15

# Combinatorics: problem session

11:00am to 1:00pm

## Location:

CS B-500, Safra campus

Speaker: Eyal Karni, BIU
Title: Combinatorial high dimensional expanders
Abstract:
An eps-expander is a graph G=(V,E) in which every set of vertices X where |X|<=|V|/2 satisfies |E(X,X^c)|>=eps*|X| . There are many edges that "go out" from any relevant set.

2019
Apr
01

# Combinatorics: Raphy Yuster (U. Haifa) "On some Ramsey type problems in tournaments"

11:00am to 1:00pm

## Location:

CS B-500, Safra campus

Speaker: Raphy Yuster, U. Haifa
Title: On some Ramsey type problems in tournaments
Abstract:
I will talk about several Ramsey type problems in tournaments guaranteeing the existence of subgraphs with certain chromatic properties.
Here are two such problems which attracted some attention recently:
1. Let g(n) be the smallest integer such that every tournament with more than g(n) vertices has an *acyclic subgraph* with chromatic number larger than n.
It is straightforward that Omega(n) <= g(n) <= n^2. An improvement of both bounds is presented.

2019
Mar
18

# Combinatorics: Arindam Banerjee (RMVERI), TBA

11:00am to 1:00pm

## Location:

CS B-500, Safra campus

Speaker: Arindam Banerjee, RMVERI
Title: Castelnuovo-Mumford Regularity, Combinatorics and Edge Ideals.
Abstract: