Large deviations for cluster size distributions in a continuous classical many-body system

TL;DR

This paper establishes a large deviations principle for cluster size distributions in a classical particle system with Lennard-Jones interactions, and analyzes the asymptotic behavior of the rate function in low-temperature, dilute limits.

Contribution

It derives an explicit large deviations principle for cluster sizes and proves the $ ext{Gamma}$-convergence of the rate function in low-temperature, low-density regimes, revealing dominant cluster sizes.

Findings

Large deviations principle for cluster size distribution derived.

Explicit limiting rate function identified in low-temperature, dilute limit.

One cluster size becomes dominant depending on the parameter $ u$.

Abstract

An interesting problem in statistical physics is the condensation of classical particles in droplets or clusters when the pair-interaction is given by a stable Lennard-Jones-type potential. We study two aspects of this problem. We start by deriving a large deviations principle for the cluster size distribution for any inverse temperature $\beta\in (0,\infty)$ and particle density $\rho\in(0,\rho_{\mathrm{cp}})$ in the thermodynamic limit. Here $\rho_{\mathrm{cp}}>0$ is the close packing density. While in general the rate function is an abstract object, our second main result is the $\Gamma$-convergence of the rate function toward an explicit limiting rate function in the low-temperature dilute limit $\beta\to \infty$, $\rho\downarrow0$ such that $-\beta^{-1}\log\rho\to\nu$ for some $\nu\in(0,\infty)$. The limiting rate function and its minimisers appeared in recent work, where the temperature and the particle density were coupled with the particle number. In the decoupled limit considered here, we prove that just one cluster size is dominant, depending on the parameter $\nu$. Under additional assumptions on the potential, the $\Gamma$-convergence along curves can be strengthened to uniform bounds, valid in a low-temperature, low-density rectangle.