Seminars Sorted by Series

Following Birkhoff's proof of the Pointwise Ergodic Theorem, it has been studied whether convergence still holds along various subsequences. In 2020, Bergelson and Richter showed that under the additional assumption of unique ergodicity, pointwise...

Ever since Furstenberg proved his multiple recurrence theorem, the limiting behaviour of multiple ergodic averages along various sequences has been an important area of investigation in ergodic theory. In this talk, I will discuss averages along...

We will discuss a version of the Green--Tao arithmetic regularity lemma and counting lemma which works in the generality of all linear forms. In this talk we will focus on the qualitative and algebraic aspects of the result.

In these two talks, I will discuss the structure of certain varieties that depend functorially on the choice of a finite-dimensional vector space. Examples include the variety of d-way tensors of "slice rank" at most k and the variety of degree-d...

In these two talks, I will discuss the structure of certain varieties that depend functorially on the choice of a finite-dimensional vector space. Examples include the variety of d-way tensors of "slice rank" at most k and the variety of degree-d...

In model theory Fraisse limits are certain highly homogeneous countable structures -- examples include the rational numbers as the unique dense linear order without endpoints, and the Rado graph as the "unique infinite random graph".  I will discuss...

The goal of this learning seminar is to explain some of the core model theoretic notions which are behind Tao’s algebraic regularity lemma about definable graphs in finite fields (Tao 2012).

We will assume minimal knowledge of model theory and...

We will survey general definitions and facts about ultrafilters, and how the algebraic operations on the integers extend to the space of ultrafilters. We will also discuss some applications in combinatorial number theory and ergodic theory.

The inverse theorem for the Gowers U^{s+1}-norms has a central place in modern additive combinatorics, but all known proofs of it are difficult and most do not give effective bounds.

Over this seminar and the next, I will give an outline of a proof...

The inverse theorem for the Gowers U^{s+1}-norms has a central place in modern additive combinatorics, but all known proofs of it are difficult and most do not give effective bounds.

Over this seminar and the next, I will give an outline of a proof...

The "intersectivity lemma" states that if a ∈ (0,1) and A_n, n ∈ N,  are measurable sets in a probability space (X,m) satisfying  m(A_n) ≥ a for all n, then there exist a subsequence n_k, k ∈ N, which has positive upper density and such that the...

The notion of strong stationarity was introduced by Furstenberg and Katznelson in the early 90's in order to facilitate the proof of the density Hales-Jewett theorem. It has recently surfaced that this strong statistical property is shared by...

A density theorem for L-functions is quantitative measure of the possible failure of the Riemann Hypothesis. In his 1990 ICM talk, Sarnak introduced the notion of density theorems for families of automorphic forms, measuring the possible failure of...

Sets of recurrence were introduced by Furstenberg in the context of ergodic theory and have an equivalent combinatorial characterization as intersective sets, an observation which has led to interesting connections between these areas.

Originally...

In 1976, Gérard Rauzy proved a characterization of deterministic numbers: y is deterministic iff for any normal number x, x+y is also normal. During my lecture I willdiscuss  how normal and deterministic numbers behave under arithmetic operations. ...

During the 2026-27 academic year the School will have a special program on Conformally Symplectic Dynamics and Geometry. Michael Hutchings, University of California, Berkeley will be the Distinguished Visiting Professor.

The purpose of this special...

This will be a survey talk about recent progress on pointwise convergence problems for multiple ergodic averages along polynomial orbits and their relations with the Furstenberg-Bergelson-Leibman conjecture.

Given a topological dynamical system $(X,T)$ a bounded sequence $(a_n)$ and $f\in C(X)$ we are interested in the asymptotic behavior of $$\frac{1}{\sum_{n\leq N}|a_n|}\sum_{n\leq N}a_nf(T^nx)$$

The restriction conjecture, one of the most central problems in harmonic analysis, studies the Fourier transform of functions defined on curved surfaces; specifically, it claims that the level sets of such Fourier transforms are relatively small...

A number is called y-smooth if all of its prime factors are bounded above by y. The set of y-smooth numbers below x forms a sparse subset of the integers below x as soon as x is sufficiently large in terms of y. If f_1, …, f_r \in Z[x_1,…,x_s] is a...

A word on d letters is an element of the free group of rank d, say, with basis x_1,…,x_d. Given a word w=w(x_1,…,x_d) on d letters, for every group G, there is a word map w:G^d—> G given by substituting the x_i’s with elements of G. We say that a...

A famous conjecture of Littlewood states that the Fourier transform of every set of N integers has $l^1$ norm at least log(N), up to a constant multiplicative factor. This was proved independently by McGehee-Pigno-Smith and Konyagin in the 1980s...

The talk will consists of a long historical introduction to  the topic of deviation
of ergodic averages for locally Hamiltonian flows on compact surafces  as well as
some current results obtained in collaboration with Corinna Ulcigrai  and Minsung...

The celebrated product theorem says if A is a generating subset of a finite simple group of Lie type G, then |AAA| \gg \min \{ |A|^{1+c}, |G| \}. In this talk, I will show that a similar phenomenon appears in the continuous setting: If A is a subset...

A discrete subgroup of PSL(2,C) is called a Kleinian group. I will present  a criterion on  when a discrete faithful representation of a Kleinian group into PSL(2,C) is a conjugation, or equivalently  a criterion on when an equivariant embedding of...

If a set of integers is syndetic (finitely many translates cover the integers), must it contain two integers whose ratio is a square?  No one knows.  In the broader context of the disjointness between additive and multiplicative configurations and...

A conjecture of Erdős states that for every large enough prime q, every reduced residue class modulo q is the product of two primes less than q. I will discuss my on-going work with Kaisa Matomäki establishing among other things a ternary variant of...