Putting Pressure Under Pressure: On the Status of Classical Pressure in Special Relativity

TL;DR

This paper argues that classical pressure, like temperature, fails in relativistic contexts, challenging existing assumptions and suggesting a new thermodynamic limit for relativistic systems.

Contribution

It demonstrates that classical pressure does not remain invariant in relativity, proposing a new thermodynamic limit to address this issue.

Findings

Classical pressure breaks down in relativistic settings.

Relativistic pressure is not Lorentz invariant.

A new thermodynamic limit (u → 0) is proposed.

Abstract

Much of the century-old debate surrounding the status of thermodynamics in relativity has centered on the search for a suitably relativistic temperature; recent works by Chua (2023) and Chua and Callender (forthcoming) have suggested that the classical temperature concept -- consilient as it is in classical settings -- 'falls apart' in relativity. However, these discussions typically assume an unproblematic Lorentz transformation for -- specifically, the Lorentz invariance of -- the pressure concept. Here I argue that, just like the classical temperature, the classical concept of pressure breaks down in relativistic settings. I discuss how this might suggest a new thermodynamic limit -- a u --> 0 limit -- without which an unambiguous thermodynamic description of systems doesn't emerge.