Microscopic statistical basis of classical Thermodynamics of finite systems

TL;DR

This paper revises classical thermodynamics for finite systems by emphasizing the importance of phase separation and fluctuations, challenging traditional assumptions based on the thermodynamic limit, and extends the applicability to nuclei and astrophysical systems.

Contribution

It introduces a microscopic statistical framework that accounts for phase transitions and fluctuations in finite systems, moving beyond the thermodynamic limit assumptions.

Findings

Heat can flow from cold to hot at phase separation.

Thermo-statistics applies to nuclei and astronomical systems.

Phase space similarities between nuclei and stellar systems.

Abstract

Heat can flow from cold to hot at any phase separation. Therefore Lynden-Bell's gravo-thermal catastrophe must be reconsidered. The original objects of Thermodynamics, the separation of phases at first order phase transitions, like boiling water in steam engines, are not described by a single canonical ensemble. Inter-phase fluctuations are not covered. The basic principles of statistical mechanics, especially of phase transitions have to be reconsidered without the use of the thermodynamic limit. Then thermo-statistics applies also to nuclei and large astronomical systems. A lot of similarity exists between the accessible phase space of fragmenting nuclei and inhomogeneous multi stellar systems.