Statistical Mechanics of Interacting Systems: The Method of Quantized Fields

Raj K. Pathria, Paul D. Beale

Klaus Hepp, Élliott H. Lieb

Osvaldo Civitarese, Manuel Gadella

Chiara Saffirio

The derivation of effective macroscopic theories approximating microscopic systems of interacting particles is a major question in non-equilibrium statistical mechanics. In these notes we present an approximation of systems made by many fermions interacting via inverse power law potentials in the mean-field and semiclassical regimes, reviewing the material presented at the 11th summer school "Methods and Models of Kinetic Theory" held in Pesaro in June 2022. More precisely, we focus on weakly interacting fermions whose collective effect can be approximated by an averaged potential in convolution form, and review recent mean-field techniques based on second quantization approaches. As a first step we obtain a reduced description given by the time-dependent Hartree-Fock equation. As a second step we look at longer time scales where a semiclassical description starts to be relevant and approximate the many-body dynamics with the Vlasov equation, which describes the evolution of the effective probability density of particles on the one particle phase space.

Xu‐Bo Zou, Jing‐Bo Xu

The system of a two-level atom interacting with a quantized radiation field in a gravitational field is studied by making use of a dynamical algebraic method. A full quantum treatment of the internal and external dynamics of the atom is given and an exact expression for the time evolution operator of the system is obtained. The influence of the gravitational field on the collapses and revivals of the atomic population, sub-Poissonian statistics, radiation force, atomic momentum diffusion, and squeezing of the radiation field is also investigated.