2020 Jan 02

# Groups & Dynamics Seminar. Maria Gerasimova (BIU) : “Isoperimetry, Littlewood functions, and unitarisability of group”

10:00am to 11:00am

## Location:

Ross 70 a
Let Γ be a discrete group. A group Γ is called unitarisable if for any Hilbert space H and
any uniformly bounded representation π : Γ → B(H) of Γ on H there exists a bounded operator
S : H → H such that S^{−1}π(g)S is a unitary representation for any g ∈ Γ. It is well known that
amenable groups are unitarisable. It has been open ever since whether amenability characterises unitarisability of groups.
Dixmier: Are all unitarisable groups amenable?
One of the approaches to study unitarisability is related to the space of the Littlewood functions
2020 Jan 08

# Special Analysis Seminar: Andrew Ahn (MIT) "Largest Singular Values of Products of \beta-Ensembles"

2:00pm to 3:00pm

## Location:

221B

Title:Largest Singular Values of Products of \beta-Ensembles

2020 Mar 31

# Or Landesberg

12:00pm to 1:00pm

2019 Dec 26

# Avinoam Mann (HUJI): Growth of groups and the word problem

12:00pm to 1:00pm

## Location:

Seminar room 209, Manchester building
2019 Dec 25

# Special dynamics seminar: Asaf Katz (Chicago) - Measure rigidity of Anosov flows via the factorization method

1:30pm to 3:30pm

## Location:

Ross 70
Title - Measure rigidity of Anosov flows via the factorization method.

Abstract: Anosov flows are central objects in dynamics, generalizing the basic example of a geodesic flow over a Riemann surface.

In the talk we will introduce those flows and their dynamical behavior.
Moreover, we show how the factorization method, pioneered by Eskin and Mirzakhani in their groundbreaking work about measure rigidity for the moduli space of translation surfaces, can be adapted to smooth ergodic theory and in particular towards the study of Anosov flows.
2020 Jan 09

# Ted Chinburg (U Penn): Using capacity theory to plug leaks

12:00pm to 1:00pm

## Location:

Manchester Building, Room 209
January 9, 12:00-13:00, Seminar room 209, Manchester building.
2019 Dec 18

# Logic Seminar - Jouko Vaananen

11:00am to 1:00pm

## Location:

Ross building - Room 63

Jouko Vaananen will speak about some new infinitary logics.

On some new infinitary logics

Abstract:
2019 Dec 18

# Special Analysis and Mathematical Physics Seminar: Eliran Subag (Courant) "Spherical spin glass models"

2:30pm to 3:30pm

## Location:

221B

Title: Spherical spin glass models

Abstract: In the 70s, physicists proposed several models fordisordered magnetic alloys called spin glass models. Mathematically, thespherical models are random functions on the sphere in high-dimensions, andmany of the questions physicists are interested in can be phrased aspurely mathematical questions about geometric properties, extreme values,critical points, and Gibbs measures of random functions and the interplaybetween them.

2019 Dec 31

# Mike Hochman (HUJI) Equidistribution for toral endomorphisms

2:00pm to 3:00pm

## Location:

Ross 70

Abstract: Host proved a strengthening of Rudolph and Johnson's measure rigidity theorem: if a probability measure is invariant, ergodic and has positive entropy for the map x2 mod 1, then a.e. point equidisitrbutes under x3 mod 1. Host also proved a version for toral endomorphisms, but its hypotheses are in some ways too strong, e.g. it requires one of the maps to be expanding, so it does not apply to pairs of  automorphisms. In this talk I will present an extension of Host's result (almost) to its natural generality.
2020 Apr 27

# Combinatorics: Noam Lifshitz (HUJI)

11:00am to 1:00pm

## Location:

Zoom

Speaker: Noam Lifshitz (HUJI)

Title: Forbidden intersections for permutations
2020 Jan 20

# Combinatorics: Wojciech Samotij (TAU)

10:00am to 12:00pm

## Location:

C-400, CS building

Title: The lower tail for triangles in random graphs

Abstract:
2020 Jan 06

# Combinatorics: Sarah Peluse (Oxford)

10:00am to 12:00pm

## Location:

C-400, CS building

Speaker: Sarah Peluse (Oxford)

Title: Bounds in the polynomial Szemer\'edi theorem
2020 Mar 23

# Combinatorics:

Repeats every week every Monday until Mon Jun 29 2020 except Mon Apr 06 2020.
11:00am to 1:00pm

11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm

Manchester 110

Speaker: TBA

Title: TBA

Abstract: TBA
2020 Jan 27

# Combinatorics: Chaya Keller (Ariel)

10:00am to 12:00pm

## Location:

C-400, CS building

Title: The epsilon-t-net problem

Abstract:

In this talk we study a natural generalization of the classical \eps-net problem (Haussler-Welzl 1987), which we call 'the \eps-t-net problem': Given a hypergraph on n vertices and parameters t and \eps , find a minimum-sized family S of t-element subsets of vertices such that each hyperedge of size at least \eps n  contains a set in S. When t=1, this corresponds to the \eps-net problem.
2020 Jan 13

# Combinatorics: Michael Simkin (HUJI)

10:00am to 12:00pm

## Location:

C-400, CS building

Title: A randomized construction of high girth regular graphs

Abstract: We describe a new random greedy algorithm for generating regular graphs of high girth: Let $k > 2$ and $0 < c < 1$ be fixed. Let $n$ be even and set $g = c \log_{k-1} (n)$. Begin with a Hamilton cycle $G$ on $n$ vertices. As long as the smallest degree $\delta (G)<k$, choose, uniformly at random, two vertices $u,v \in V(G)$ of degree $\delta(G)$ whose distance is at least $g-1$. If there are no such vertex pairs, abort. Otherwise, add the edge $uv$ to $E(G)$.