Évènements

Dynamical properties of rough delay equations

Catégorie d'évènement : Séminaire Probabilités et Statistique Date/heure : 3 mars 2022 10:45-11:45 Lieu : Lien Teams Oratrice ou orateur : Mazyar Ghani Varzaneh (Technische Universität Berlin) Résumé :

This talk aims to incorporate two subjects for developing a framework for studying the long-time behavior solution of singular delay equations. Singular delay equations fail to induce the flow property. Accordingly, for a long time, many people have believed it is not possible to apply the idea of random dynamical systems to this family of equations.
In this talk, we claim, is possible. The main trick is to regard the solution in the language of the Rough path and then construct the flow property in a bundle-like family of Banach spaces. The main challenge here is to prove the Multiplicative Ergodic Throem in this new framework. After proving this crucial theorem, we can generate the Lyapunov exponents. These exponents can be regarded as a generalization of eigenvalues. We then apply these theorems to prove the invariant manifolds in our setting. The main tools here are the rough path theory and random dynamical systems.
This talk is based on my doctoral thesis. I recently have defended my thesis in February.


Gowers uniformity of thin subsets of primes

Catégorie d'évènement : Séminaire de Théorie des Nombres de Nancy-Metz Date/heure : 3 mars 2022 14:30-15:30 Lieu : Salle de séminaire de Théorie des Nombres virtuelle Oratrice ou orateur : Fernando Xuancheng Shao (University of Kentucky) Résumé :

A celebrated theorem of Green-Tao asserts that the set of primes contains arbitrarily long arithmetic progressions. In fact, they count asymptotically the number of k-term arithmetic progressions in primes up to a threshold. Their work involves discorrelation estimates between primes and nilsequences, which imply that the set of primes is Gowers uniform. In this talk I will discuss results of this type for primes restricted to short intervals and in arithmetic progressions. For example, we prove that the set of primes in (X, X+H]  with H > X^{5/8+\varepsilon} is Gowers uniform; we also prove that, for almost all q < X^{1/4-\varepsilon}, the set of primes up to X in a coprime residue class a\pmod{q} is Gowers uniform. This is based on joint works with K. Matomäki, J. Teräväinen, T. Tao.