Temperature inversion in long-range interacting systems

TL;DR

This paper demonstrates how long-range interactions in certain systems can spontaneously produce temperature inversions, contrasting with short-range systems that tend to reach uniform temperature states.

Contribution

It introduces a mechanism for temperature inversion in long-range interacting systems via impulsive perturbations, supported by models like mean-field and self-gravitating systems.

Findings

Temperature inversions occur in long-range systems after perturbation.

Short-range systems relax to uniform temperature states.

Long-range interactions lead to nonequilibrium stationary states with temperature inversion.

Abstract

Temperature inversions occur in nature, e.g., in the solar corona and in interstellar molecular clouds: somewhat counterintuitively, denser parts of the system are colder than dilute ones. We propose a simple and appealing way to spontaneously generate temperature inversions in systems with long-range interactions, by preparing them in inhomogeneous thermal equilibrium states and then applying an impulsive perturbation. In similar situations, short-range systems would typically relax to another thermal equilibrium, with uniform temperature profile. By contrast, in long-range systems, the interplay between wave-particle interaction and spatial inhomogeneity drives the system to nonequilibrium stationary states that generically exhibit temperature inversion. We demonstrate this mechanism in a simple mean-field model and in a two-dimensional self-gravitating system. Our work underlines the crucial role the range of interparticle interaction plays in determining the nature of steady states out of thermal equilibrium.