Author: mbaldovin

M. Baldovin, G. Vallet, G. Hagel, E. Trizac, C. Champenois
Self-diffusion in a strongly coupled non-neutral plasma
Phys. Rev. A 109, 043116 (2024)

We propose a joint experimental and theoretical approach to measure the self-diffusion in a laser-cooled trapped ion cloud where part of the ions are shelved in a long-lived dark state. The role of the self-diffusion coefficient in the spatial organisation of the ions is deciphered, following from the good agreement between the experimental observations and the theoretical predictions. This comparison furthermore allows to deduce the temperature of the sample. Protocols to measure the self-diffusion coefficient are discussed, in regard with the control that can be reached on the relevant time scales through the dressing of the atomic levels by laser fields.

M. Baldovin, R. Marino, A. Vulpiani.
Ergodic observables in non-ergodic systems: the example of the harmonic chain
Physica A: Statistical Mechanics and its Applications 630, 129273 (2023)

In the framework of statistical mechanics the properties of macroscopic systems are deduced starting from the laws of their microscopic dynamics. One of the key assumptions in this procedure is the ergodic property, namely the equivalence between time averages and ensemble averages. This property can be proved only for a limited number of systems; however, as proved by Khinchin, weak forms of it hold even in systems that are not ergodic at the microscopic scale, provided that extensive observables are considered. Here we show in a pedagogical way the validity of the ergodic hypothesis, at a practical level, in the paradigmatic case of a chain of harmonic oscillators. By using analytical results and numerical computations, we provide evidence that this non-chaotic integrable system shows ergodic behaviorin the limit of many degrees of freedom. In particular, the Maxwell-Boltzmann distribution turns out to fairly describe the statistics of the single particle velocity. A study of the typical time-scales for relaxation is also provided.

Welcome to the new version of my webpage. As before, I will use this space to keep track of the main results of my research projects and to share (hopefully useful) news about conferences, events, interesting papers and so on.