On relativistic thermodynamics

TL;DR

This paper clarifies the application of general thermodynamic principles to relativistic systems, reaffirming Einstein and Planck's results and discussing the operational significance of temperature in relativistic contexts.

Contribution

It presents a unified thermodynamic framework for relativistic systems, clarifying temperature definition and its implications, distinct from non-relativistic thermodynamics.

Findings

Unambiguous definition of relativistic temperature as energy change rate at constant momentum.

Confirmation that relativistic thermodynamics aligns with Einstein and Planck's original results.

Discussion on alternative measures of energy and entropy involving momentum transfer.

Abstract

'Relativistic thermodynamics' should be understood not as a generalization of a non-relativistic theory but as an application of a general thermodynamic framework, neutral as to spacetime setting and allowing arbitrary conserved quantities, to the specific case of relativity. That framework gives an unambiguous result as to the thermodynamics of relativistically moving systems (an answer coinciding with Einstein's, and Planck's, original results.) Thermodynamic temperature is unambiguously defined as rate of change of energy with entropy at constant momentum; that said, its operational significance is limited and other measures of energy/entropy covariance, which incorporate momentum transfer, are often more useful.