Soutenances de Thèses 2022

Leonardo MAZZA

Vendredi 8 avril 2022
Grand amphithéâtre Bâtiment Pascal n° 530
Soutenance Habilitation à diriger des recherches

Topological matter and out-of-equilibrium physics in cold-atom setups

The study of ultra-cold gases is currently offering a new vision of many-body quantum physics. In this seminar I will briefly overview my recent contributions to the field, focusing on topological physics and out-of-equilibrium dynamics.

In the first part, motivated by the studies on the quantum Hall effect and Chern insulators with cold atoms, I will discuss my recent contributions on the fractional statistics of the quasiholes of several paradigmatic states, with a specific focus on Laughlin and Halperin wavefunctions. The goal is to show that it is possible to extract information on the statistics using only density-profile measurements and without resorting in any way to interference schemes.

In the second part of the talk I will discuss my contributions to the field of out-of-equilibrium dynamics of correlated quantum gases, focusing on the effect of two-body losses in one-dimensional setups. Motivated by recent experiments, I will show that losses can induced intriguing transient dynamics and even stabilize entangled stationary states. The strongly-dissipative limit, also known as quantum Zeno limit, lends itself to an insightful analytical description in terms of appropriate rate equations.

Jury : Isabelle Bouchoule (Institut d’Optique), Nigel R. Cooper (University of Cambridge), Mark O. Goerbig (LPS Orsay), Anna Minguzzi (LPMMC Grenoble), Sylvain Nascimbene (LKB, Collège de France), Tommaso Roscilde (ENS Lyon)

Francesco MORI

Vendredi 10 juin 2022
Petit amphithéâtre Bâtiment Pascal n° 530
Soutenance de thèse

Extreme value statistics of stochastic processes : from Brownian motion to active particles

Rare extreme events tend to play a major role in a wide range of contexts, from finance to climate. Hence, understanding their statistical properties is a relevant task, which opens the way to many applications. In this thesis, we investigate the extremal properties of several stochastic processes, including Brownian motion (BM), active particles, and BM with resetting.  In the first part, we investigate the times at which extrema of one-dimensional stochastic processes occur. In particular, in the case of a BM of fixed duration, we compute the probability distribution of the time between the global maximum and the global minimum. Moreover, we derive the distribution of the time of the maximum for stationary stochastic processes, both at equilibrium and out-of-equilibrium. This analysis leads to the formulation of a simple criterion to detect nonequilibrium fluctuations in steady states. In the second part, we focus on the run-and-tumble particle (RTP) model. We compute exactly the survival probability for a single RTP in d dimensions, showing that this quantity is completely universal, i.e., independent of d and the speed fluctuations of the particle. We extend this universality to other observables (time of the maximum and records) and generalized RTP models. Moreover, we also investigate the position distribution of a single RTP at late times. We show that, under certain conditions, a condensation transition can be observed in the large-deviation regime where the particle is far from its starting position. Finally, we introduce a new technique, analog to the Hamilton-Jacobi-Bellman equation, to optimally control a dynamical system through stochastic resetting.

Jury : Satya Majumdar (directeur de thèse), David Dean (rapporteur), Matteo Marsili (rapporteur), Martin Evans, Joachim Krug, Cécile Monthus, Grégory Schehr, Raphaël Voiturier