Given a set X, the notion of VC-dimension provides a way to measure randomness in collections of subsets of X. Specifically, the VC-dimension of a collection S of subsets of X is the largest integer d (if it exists) such that some d-element subset Y of X is ""shattered"" by S, meaning that every subset of Y can be obtained as the intersection of Y with some element of S. In this talk, we will focus on the case that X is a group G, and S is the collection of left translates of some fixed subset A of G.

The study of the representations theoretic properties of the group of diffeormorphisms of locally compact non compact Riemmanian manifolds which equal to the identity outside a compact set is is linked to a natural quasi invariant action of the group which moves all points of a Poisson point process according to the diffeomorphism (Gelfand-Graev-Vershik and Goldin et al.). Neretin noticed that the local diffeomorphism group is a subgroup of a larger group which he called GMS and that GMS also acts in a similar manner on the Poisson point process.

A major difficulty in finding polynomial patterns in primes is the need to understand their distribution properties at short scales. We describe how for some polynomial configurations one can overcome this problem by concatenating short scale behavior in "many directions" to long scale behavior for which tools from additive combinatorics are available.

A classical theorem of Erdos and Turan states that if a monic polynomial has small values on the unit circle (relative to its constant coefficient), then its zeros cluster near the unit circle and are close to being equidistributed in angle. In February 2018, K. Soundararajan gave a short and elementary proof of their result using Fourier analysis. I'll present this new proof.

Since the seminal work of Arnold on the Euler equations (1966), many equations in hydrodynamics were shown to be geodesic equations of diffeomorphism groups of manifolds, with respect to various Sobolev norms. This led to new ways to study these PDEs, and also initiated the study of of the geometry of those groups as (infinite dimensional) Riemannian manifolds.

Speaker: Joel Friedman, UBC Title: Open Problems Related to the Zeta Functions Abstract: We express some open problems in graph theory in terms of Ihara graph zeta functions, or, equivalently, non-backtracking matrices of graphs. We focus on "expanders" and random regular graphs, but touch on some seemingly unrelated problems encoded in zeta functions. We suggest that zeta functions of sheaves on graphs may have relevance to complexity theory and to questions of Stark and Terras regarding whether coverings of a fixed graph can ramify like number field extensions.

Speaker: Michael Farber,  Queen Mary

Title: Multi-parameter random simplicial complexes

Read more about Combinatorics: Michael Farber (Queen Mary), "Multi-parameter random simplicial complexes"

Speaker: Zur Luria, ETH Title: New bounds for the n-queen's problem Abstract: The famous n-queens problem asks: In how many ways can n nonattacking queens be placed on an n by n chessboard? This question also makes sense on the toroidal chessboard, in which opposite sides of the board are identified. In this setting, the n-queens problem counts the number of perfect matchings in a certain regular hypergraph. We give an extremely general bound for such counting problems, which include Sudoku squares and designs.