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

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.