Between equilibrium and fluctuation: Einstein's heuristic argument and Boltzmann's principle

Fuente: arXiv
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Main Authors: Pérez, Enric, Gil, Antonio
Format: Preprint
Published: 2026
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author Pérez, Enric
Gil, Antonio
author_facet Pérez, Enric
Gil, Antonio
contents We critically revisit Einstein's 1905 heuristic argument for lightquanta, considering its internal coherence and the scope of its applicability. We argue that Einstein's reasoning, often celebrated for its originality, is ambiguous because it can be understood as a fluctuation or as a comparison between equilibrium states. A historical and conceptual analysis of Einstein's use of Boltzmann's principle in those years reveals his evolving stance on its meaning and the role of probability, as well as his persistent doubts about the nature of radiation. We use our analysis to examine the limitations of extending the notion of Einstein's lightquanta across the electromagnetic spectrum: the relevant parameter is not the frequency, but the occupancy number.
format Preprint
id arxiv_https___arxiv_org_abs_2602_10738
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Between equilibrium and fluctuation: Einstein's heuristic argument and Boltzmann's principle
Pérez, Enric
Gil, Antonio
History and Philosophy of Physics
Statistical Mechanics
Quantum Physics
We critically revisit Einstein's 1905 heuristic argument for lightquanta, considering its internal coherence and the scope of its applicability. We argue that Einstein's reasoning, often celebrated for its originality, is ambiguous because it can be understood as a fluctuation or as a comparison between equilibrium states. A historical and conceptual analysis of Einstein's use of Boltzmann's principle in those years reveals his evolving stance on its meaning and the role of probability, as well as his persistent doubts about the nature of radiation. We use our analysis to examine the limitations of extending the notion of Einstein's lightquanta across the electromagnetic spectrum: the relevant parameter is not the frequency, but the occupancy number.
title Between equilibrium and fluctuation: Einstein's heuristic argument and Boltzmann's principle
topic History and Philosophy of Physics
Statistical Mechanics
Quantum Physics
url https://arxiv.org/abs/2602.10738