Thermodynamics of Superfluidity

TL;DR

This paper introduces a new additive integral of motion specific to superfluids, enabling a comprehensive thermodynamic analysis that extends traditional criteria to finite temperatures.

Contribution

It presents a novel superfluid-specific integral of motion and derives new thermodynamic inequalities that generalize the Landau criterion at finite temperatures.

Findings

New superfluid integral of motion identified

Thermodynamic inequalities replacing Landau criterion derived

Extended thermodynamic space including superfluid velocity analyzed

Abstract

New, superfluid specific additive integral of motion is found. This facilitates investigation of general thermodynamic equilibrium conditions for superfluid. The analysis is performed in an extended space of thermodynamic variables containing (along with the usual thermodynamic coordinates such as pressure and temperature) superfluid velocity and momentum density. The equilibrium stability conditions lead to thermodynamic inequalities which replace the Landau superfluidity criterion at finite temperatures.