Influence of the interaction range on the thermostatistics of a classical many-body system

TL;DR

This study investigates how the interaction range in a one-dimensional classical rotator system influences its statistical behavior, revealing a transition from Maxwellian to fat-tailed distributions linked to nonextensive statistics.

Contribution

It provides numerical evidence that the interaction range determines whether the system follows Boltzmann-Gibbs or nonextensive statistical mechanics.

Findings

For large interaction range, the system exhibits Maxwellian distributions.

For small or comparable to unity interaction range, fat-tailed q-Gaussian distributions emerge.

Results support the relevance of nonextensive statistical mechanics in long-range interacting systems.

Abstract

We numerically study a one-dimensional system of $N$ classical localized planar rotators coupled through interactions which decay with distance as $1/r^\alpha$ ($\alpha \ge 0$). The approach is a first principle one (\textit{i.e.}, based on Newton's law), and yields the probability distribution of momenta. For $\alpha$ large enough and $N\gg1$ we observe, for longstanding states, the Maxwellian distribution, landmark of Boltzmann-Gibbs thermostatistics. But, for $\alpha$ small or comparable to unity, we observe instead robust fat-tailed distributions that are quite well fitted with $q$-Gaussians. These distributions extremize, under appropriate simple constraints, the nonadditive entropy $S_q$ upon which nonextensive statistical mechanics is based. The whole scenario appears to be consistent with nonergodicity and with the thesis of the $q$-generalized Central Limit Theorem.