For the academic year 2025-26, the seminar is organised by Víťa Kala and myself, and runs on Wednesdays 14:00 in room K6.
The seminar is intended for students and faculty members, so the level of the talks should be accessible to these people.
We have a mailing list for announcing upcoming talks. If you wish to subscribe to the mailing list, please contact any of the organisers.
I will give a brief introduction to well-rounded lattices and to their utility in (post-quantum) security. We will see how the lattice theta series naturally arises in these contexts and discuss its connections to well-rounded lattices.
A Hilbert cube of dimension d is the set of integers H(a0;a1,...,ad) = {a0 + {0,a1} + ··· + {0,ad} = a0 + ε1a1 + ... + εdad : εi ∈{0,1}}. Brown, Erdős and Freedman asked whether the maximal dimension of a Hilbert cube in the set S = {n² : n ∈ N} of integer squares is absolutely bounded or not. Dietmann and Elsholtz proved that if H(a0;a1,...,ad) ⊂ S ∩ [0, N], then d ≤ 7 log log N for all sufficiently large values of N. Here we prove that there exist at least ≫ N^(1/8) Hilbert cubes H(a0;a1,a2,a3) with a0, a1, a2, a3 ∈ [0, N] in the set of squares. Moreover, we prove that for each i,j ∈ {0,1,2,3} with i<j, the set {ai/aj : H(a0;a1,a2,a3) ⊂ S} is dense in the set of positive real numbers (in the Euclidean topology). The talk is based on a joint work with Andrew Bremner and Christian Elsholtz.
A (positive definite and integral) quadratic form f is called irrecoverable (from its subforms) if there is a quadratic form F that represents all proper subforms except for f itself, and such a quadratic form F is called an isolation of f. In this talk, we present recent advances on irrecoverable quadratic forms and discuss their possible generalizations.
In this talk, I will discuss the Kaplansky radical of a field, an object introduced by Irving Kaplansky in the 1960s to characterize fields with a unique non-split quaternion algebra. I will focus on the case of function fields of curves, and in particular on arithmetic curves, where I will show how the Kaplansky radical can be connected to the reduction of the curve.
I will present joint work with Maxim Gerspach on lower-order terms in Selberg's central limit theorem. In particular, we compute precise asymptotic formulas for the third moment of both the real and imaginary parts of the logarithm of the Riemann zeta function. Our results are conditional on the Riemann Hypothesis, Hejhal's triple correlation, and a new conjecture that describes the interaction between prime powers and Montgomery's pair correlation function. To support this conjecture, which we refer to as the "twisted" pair correlation conjecture, we prove it unconditionally in a limited range and under the Hardy-Littlewood conjecture in a larger range.
Abstract: Let f be a function on the natural numbers, periodic with period N>1, with f(n) taking values -1 or 1 for 0 < n < N, and f(N) = 0. In the 1950s, Erdős conjectured that for such a function f, the infinite series ∑ₙ f(n)/n is non-zero, whenever it converges. This is in the same spirit as the non-vanishing of L(1,χ) for non-principal real Dirichlet characters χ, which is an essential step in proving Dirichlet's theorem on the infinitude of primes in arithmetic progressions. In this talk, we discuss the nuances of Erdos's conjecture and present a new approach to it, which leads to its resolution in `almost all' cases. More specifically, we describe joint work with Abhishek Bharadwaj and Ram Murty in which we settle Erdős's conjecture, except for the case when N is a perfect square.
The Weil height captures the arithmetic complexity of algebraic numbers and gives a partial ordering on numbers with bounded degree. It is an important theme to characterize sets of algebraic numbers such that their height is bounded below. Such sets are said to have the Bogomolov property. In this talk, we will discuss Bogomolov property over infinite extensions for algebraic numbers and also for points on elliptic curves over infinite extensions. This is joint work with Sushant Kala.