Typicality, entropy and the generalization of statistical mechanics

Fuente: arXiv
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Main Authors: Corominas-Murtra, Bernat, Hanel, Rudolf, Jizba, Petr
Format: Preprint
Published: 2024
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author Corominas-Murtra, Bernat
Hanel, Rudolf
Jizba, Petr
author_facet Corominas-Murtra, Bernat
Hanel, Rudolf
Jizba, Petr
contents When at equilibrium, large-scale systems obey conventional thermodynamics because they belong to microscopic configurations (or states) that are typical. Crucially, the typical states usually represent only a small fraction of the total number of possible states, and yet the characterization of the set of typical states -- the typical set -- alone is sufficient to describe the macroscopic behavior of a given system. Consequently, the concept of typicality, and the associated Asymptotic Equipartition Property allow for a drastic reduction of the degrees of freedom needed for system's statistical description. The mathematical rationale for such a simplification in the description is due to the phenomenon of concentration of measure. The later emerges for equilibrium configurations thanks to very strict constraints on the underlying dynamics, such as weekly interacting and (almost) independent system constituents. The question naturally arises as to whether the concentration of measure and related typicality considerations can be extended and applied to more general complex systems, and if so, what mathematical structure can be expected in the ensuing generalized thermodynamics. In this paper we illustrate the relevance of the concept of typicality in the toy model context of the "thermalized" coin and show how this leads naturally to Shannon entropy. We also show an intriguing connection: The characterization of typical sets in terms of Renyi and Tsallis entropies naturally leads to the free energy and partition function, respectively, and makes their relationship explicit. Finally, we propose potential ways to generalize the concept of typicality to systems where the standard microscopic assumptions do not hold.
format Preprint
id arxiv_https___arxiv_org_abs_2409_06537
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Typicality, entropy and the generalization of statistical mechanics
Corominas-Murtra, Bernat
Hanel, Rudolf
Jizba, Petr
Statistical Mechanics
Information Theory
When at equilibrium, large-scale systems obey conventional thermodynamics because they belong to microscopic configurations (or states) that are typical. Crucially, the typical states usually represent only a small fraction of the total number of possible states, and yet the characterization of the set of typical states -- the typical set -- alone is sufficient to describe the macroscopic behavior of a given system. Consequently, the concept of typicality, and the associated Asymptotic Equipartition Property allow for a drastic reduction of the degrees of freedom needed for system's statistical description. The mathematical rationale for such a simplification in the description is due to the phenomenon of concentration of measure. The later emerges for equilibrium configurations thanks to very strict constraints on the underlying dynamics, such as weekly interacting and (almost) independent system constituents. The question naturally arises as to whether the concentration of measure and related typicality considerations can be extended and applied to more general complex systems, and if so, what mathematical structure can be expected in the ensuing generalized thermodynamics. In this paper we illustrate the relevance of the concept of typicality in the toy model context of the "thermalized" coin and show how this leads naturally to Shannon entropy. We also show an intriguing connection: The characterization of typical sets in terms of Renyi and Tsallis entropies naturally leads to the free energy and partition function, respectively, and makes their relationship explicit. Finally, we propose potential ways to generalize the concept of typicality to systems where the standard microscopic assumptions do not hold.
title Typicality, entropy and the generalization of statistical mechanics
topic Statistical Mechanics
Information Theory
url https://arxiv.org/abs/2409.06537