Seminars Sorted by Series

Over the last decades, following works around the Pila-Wilkie counting theorem in the context of o-minimality, there has been a surge in interest around functional transcendence results, in part due to their connection with special points...

How fast do Betti numbers grow in a congruence tower of compact arithmetic manifolds? The dimension of the middle degree of cohomology is proportional to the volume of the manifold, but away from the middle the growth is known to be sub-linear in...

Given a K3 surface $X$ over a number field $K$, we prove that the set of primes of $K$ where the geometric Picard rank jumps is infinite, assuming that $X$ has everywhere potentially good reduction. This result is formulated in the general framework...

I will discuss some new results on the structure of Selmer groups of finite Galois modules over global fields. Tate's definition of the Cassels-Tate pairing can be extended to a pairing on such Selmer groups with little adjustment, and many of the...

Consider the function field F of a smooth curve over $F_q$, with $q > 2$.

L-functions of automorphic representations of $GL(2)$ over $F$ are important objects for studying the arithmetic properties of the field $F$. Unfortunately, they can be...

Faltings proved the statement, previously conjectured by Shafarevich, that there are finitely many abelian varieties of dimension $n$, defined over a fixed number field, with good reduction outside a fixed finite set of primes, up to isomorphism. In...

A classical branching theorem of Weyl describes how an irreducible representation of compact $U(n+1)$ decomposes when restricted to $U(n)$. The local Gan-Gross-Prasad conjecture provides a conjectural extension to the setting of representations of...

I will explain some recent work on special cases of the Bloch-Kato conjecture for the symmetric cube of certain modular Galois representations. Under certain standard conjectures, this work constructs nontrivial elements in the Selmer groups of...

Sums of Dirichlet characters $\sum_{n \leq x} \chi(n)$ (where $\chi$ is a character modulo some prime $r$, say) are one of the best studied objects in analytic number theory. Their size is the subject of numerous results and conjectures, such as the...

For certain automorphic representations $\pi$ on unitary groups, we show that if $L(s, \pi)$ vanishes to order one at the center $s=1/2$, then the associated $\pi$-localized Chow group of a unitary Shimura variety is nontrivial. This proves part of...

Given an elliptic curve $E$, Kolyvagin used CM points on modular curves to construct a system of classes valued in the Galois cohomology of the torsion points of $E$. Under the conjecture that not all of these classes vanish, he gave a description...

Up to a finite covering, a sequence of nested subvarieties of an affine algebraic variety just looks like a flag of vector spaces (Noether); understanding this « up to » is a primary motivation for a fine study of finite coverings.

The aim of this...

I will discuss recent work with Harald Helfgott in which we establish roughly speaking that the graph connecting $n$ to $n \pm p$ with $p$ a prime dividing $n$ is almost "locally Ramanujan". As a result we obtain improvements of results of Tao and...

This is intended to complement the recent talk of Pham Huu Tiep in this seminar but will not assume familiarity with that talk. The estimates in the title are upper bounds of the form $|\chi(g)| \le \chi(1)^\alpha$, where $\chi$ is irreducible and $...

In the recent breakthrough on the uniform Mordell-Lang problem by Dimitrov-Gao-Habegger and Kuhne, their key result is a uniform Bogomolov type of theorem for curves over number fields. In this talk, we introduce a refinement and generalization of...

I will discuss some recent progress in analytic number theory for polynomials over finite fields, giving strong new estimates for the number of primes in arithmetic progressions, as well as for sums of some arithmetic functions in arithmetic...

We consider the standard L-function attached to a cuspidal automorphic representation of a general linear group. We present a proof of a subconvex bound in the t-aspect. More generally, we address the spectral aspect in the case of uniform parameter...

We study CM cycles on Kuga-Sato varieties over $X(N)$ via theta lifting and relative trace formula. Our first result is the modularity of CM cycles, in the sense that the Hecke modules they generate are semisimple whose irreducible components are...

For a polynomial $f\in \mathbb Q[x]$, Hilbert's irreducibility theorem asserts that the fiber $f^{-1}(a)$ is irreducible over $\mathbb Q$ for all values $a\in \mathbb Q$ outside a "thin" set of exceptions $R_f$. The problem of describing $R_f$ is...

In this talk, we prove an upper bound on the average number of 2-torsion elements in the class group of monogenised fields of any degree $n \geq 3$ and, conditional on a widely expected tail estimate, compute this average exactly. As an application...

The unbounded denominators conjecture, first raised by Atkin and Swinnerton-Dyer, asserts that a modular form for a finite index subgroup of $SL_2(\mathbb Z)$ whose Fourier coefficients have bounded denominators must be a modular form for some...

In 1986, Hooley applied (what practically amounts to) the general Langlands reciprocity (modularity) conjecture and GRH in a fresh new way, over certain families of cubic 3-folds. This eventually led to conditional near-optimal bounds for the number...

Katz and Oort raised the following question: Given an algebraically closed field $k$, and a positive integer $g > 3$, does there exist an abelian variety over k not isogenous to a Jacobian over $k$? There has been much progress on this question...

We introduce a new orbit parametrization for square roots of the class of the inverse different in rings cut out by binary forms. This parametrization has many applications of interest in arithmetic statistics; for example, we use it to prove that...

A surprising property of the cohomology of locally symmetric spaces is that Hecke operators can act on multiple cohomological degrees with the same eigenvalues. We will discuss this phenomenon for the coherent cohomology of line bundles on modular...

I will present joint work with V. Paškūnas and G. Böckle concerning deformation rings for mod $p$ Galois representations of $p$-adic local fields. After giving a short introduction to the subject, I will explain our main result which says that...

Wiles’s proof of the modularity of (semistable) elliptic curves over the rationals and Fermat’s Last Theorem relied on his invention of a modularity lifting method. There were two strands to the method:

(i) A numerical criterion to for a map of...

In 2001 Croot resolved an old conjecture of Erdos and Graham, proving that in any finite colouring of the positive integers there is a (non-trivial) monochromatic solution to 1/n_1+...+1/n_k = 1 with all n_i distinct. A natural generalisation, also...

I will explain how various results in arithmetic statistics by Bhargava, Gross, Shankar and others on 2-Selmer groups of Jacobians of (hyper)elliptic curves can be organised and reproved using the theory of graded Lie algebras, following earlier...

Let $N$ and $p$ $\geq 5$ be primes such that $p$ divides $N-1$. In his landmark paper on the Eisenstein ideal, Mazur proved the $p$-part of the BSD conjecture for the $p$-Eisenstein quotient $J^{(p)}$ of $J_0(N)$ over $\mathbf{Q}$. Using recent...

Recently, Fargues and Scholze attached a semi-simple L-parameter to any smooth irreducible representation of a p-adic reductive group, realizing the local Langlands correspondence as a geometric Langlands correspondence over the Fargues-Fontaine...

We determine the average size of the 3-torsion in class groups of $G$-extensions of a number field when $G$ is any transitive 2-group containing a transposition, for example, $D4$.  It follows from the Cohen--Lenstra--Martinet heuristics that the...

I will discuss recent work with Maksym Radziwill in which we show that for any fixed tempered cuspidal representation $\pi$ of $\mathrm{GL}(4)$ over the rationals, there exist infinitely many primitive characters $\chi$ such that the twisted $L$...

Of the $(2H+1)^n$ monic integer polynomials $f(x)=x^n+a_1 x^{n-1}+\cdots+a_n$ with $\max\{|a_1|,\ldots,|a_n|\}\leq H$, how many have associated Galois group that is not the full symmetric group $S_n$?  There are clearly $\gg H^{n-1}$ such...

Half-integral weight modular forms are classical objects with many important arithmetic applications.  In terms of automorphic representations, these correspond to objects on the metaplectic double cover of SL(2).  In this talk, I will outline a...