tbranzov

In this talk, aimed at a general audience, we will describe recent results on the characterization of norm forms—a classical object in algebraic number theory—in terms of their values at integer points. These results answer natural questions and are related to still-open conjectures of Littlewood (from 1930) and of Cassels and Swinnerton-Dyer (from 1955). The proofs rely on studying the actions of maximal tori of algebraic groups on homogeneous spaces of arithmetic origin.

Aiming to understand the relation to other "refined invariants", and especially their possible interpretation in quantum theory, we explain how to obtain a quadratic, A1-version of Donaldson-Thomas invariants from the motivic refinements first introduced in Kontsevich-Soibelman. Following ideas from Behrend, Bryan and Szendroi, we provide predictions for these invariants in a few simple examples, mainly the computation of DT invariants of A3. Our main goal is to draw relationships with the literature, including works of Levine, Denef and Loser, Azouri, Pepin-Lehaulleur, Srinivas among others. We begin with a brief introduction to A1-enumerative geometry and in the end, we pose some further questions on possible extensions of our definitions. This is joint work with Johannes Walcher. We also comment on joint work in progress with Ran Azouri.

In this talk we will explain the role that the Lie algebras play in the construction of 6-dimensional compact quotient spaces M=G/Γ, where Γ is a lattice, endowed with an invariant complex structure with holomorphically trivial canonical bundle.

Affine geometry is sometimes described as "what remains of Euclidean geometry when distances are forgotten". In this talk, I will report on a very recent discovery of an affine-invariant notion, which may be viewed as a distance from a point inside a convex domain to its boundary. This new concept stems from a suggestion of Conan Leung, who proposed to average the canonical tropical series, a fundamental notion of tropical optics, over the manifold of all tropical structures of fixed covolume on the given affine space. Very little of what we (Nikita Kalinin, Ernesto Lupercio and me) currently know, as well as necessary preliminaries, some observations and precise conjectures, will be covered during the talk, which mainly serves as an invitation to participate in developing this exciting new topic.

A complex measure $\mu$ on a $d$-dimensional Euclidean space is a crystalline measure (CM) if it is the temperate distribution, its distributional Fourier transform $\hat\mu$ is also a measure, and supports of $\mu$ and $\hat\mu$ are discrete (locally finite); $\mu$ is a Fourier quasicrystal (FQ) if, in addition, $|\mu|$ and $|\hat\mu|$ are also temperate distributions. For example, if $\mu_0$ is the sum of the unit masses at all points with integer coordinates, then by Poisson's formula $\hat\mu_0=\mu_0$. Hence, $\mu_0$ is FQ. We show a theorem of Lev-Olevskii on a sufficient condition for trivialization of FQ. Then we discuss a simple condition for CM to be FQ and present CM that is not FQ. We recall the notion of an almost periodic function, introduce the notions of almost periodic measures, distributions, sets, and show their connections with CM. In paricular, we get various uniqueness theorems for FQ. Finally, we show the description of FQ with unit masses as zeros of exponential polynomials due to Olevskii and Ulanovskii, and discuss some generalizations to zeros of Dirichlet series and to measures in a horizontal strip of finite width.

In the present talk, we will discuss the prospect of electrodynamics in quantifying the self-interaction of a non-composite charged particle. We will demonstrate that under the consideration of unique to the particle Yukawa cut-offs the radial singularity in corresponding electromagnetic field potentials’ is removed allowing the classical theory to admit exact solutions for the particle’s self-energy and anomalous g-factor.