Number Theory

I'll speak about joint work with Rachel Greenfeld and Marina Iliopoulou in which we address some classical questions concerning the size and structure of integer distance sets. A subset of the Euclidean plane is said to be an integer distance set if the distance between any pair of points in the…

Given an étale Z_p-local system of rank n on an algebraic variety X, continuous cohomology classes of the group GL_n(Z_p) give rise to classes in (absolute) étale cohomology of the variety. These characteristic classes can be thought of as p-adic analogs of Chern-Simons characteristic classes of…

A fundamental problem in the arithmetic of varieties over global fields is to determine whether they have a rational point.  As a first effective step, one can check that a variety has local points for each place.  However, this is not enough, as many classes of varieties are known to…

Some 20 years ago, Daniel Bump asked me to compute eigenfunctions of the Hecke algebra on the Shalika model of GL(2n), a variant of the Whittaker model. The result included some intriguing polynomials related to the root system of type C_n, which appeared somewhat random.  

This…

Lusztig's theory of character sheaves for connected reductive groups is one of the most important developments in representation theory in the last few decades. I will give an overview of this theory and explain the need, from the perspective of the representation theory of p-adic groups, of a…

There have been several recent approaches to defining a moduli space of L-parameters over Z[1/p], in order to obtain refined versions of the local Langlands conjecture ``at all primes away from p at once''. The components of this space are expected to be closely related to blocks in the category…

We care about arithmetic invariants of polynomial equations / motives e.g. conductors or L-functions, which (conjecturally) are often automorphic and related to cycles on Shimura varieties. In this talk, I will focus on L-functions of Asai motives (e.g. Rankin-Selberg motives for GL_n x GL_n)…

Abstract: The arithmetic quantum unique ergodicity (AQUE) conjecture predicts that the L^2 mass of Hecke-Maass cusp forms on an arithmetic hyperbolic manifold becomes equidistributed as the Laplace eigenvalue grows. If the underlying manifold is non-compact, mass could “escape to infinity”, and…

The general goal of Higher Hida theory is to define and understand the ordinary part of integral coherent cohomology of Shimura varieties. In this talk we will focus on the simplest example of a Shimura variety for a non-split reductive group. We describe the results, notably vanishing…