Superfluid Dynamics, Equilibrium Conditions, and Centripetal Forces

TL;DR

This paper revisits superfluid thermodynamics, deriving equilibrium density and pressure distributions influenced by heat currents and showing that two-fluid hydrodynamics fundamentally reflects equilibrium entropy conditions.

Contribution

It provides explicit formulas for equilibrium states in superfluids and clarifies the theoretical basis of two-fluid hydrodynamics as equilibrium conditions.

Findings

Counter heat currents cause pressure depression and centripetal forces.

Equilibrium conditions are expressed as maximal entropy configurations.

Two-fluid hydrodynamics is an assembly of equilibrium expressions.

Abstract

Thermodynamics of superfluids is revisited, clarifying two points. First, the density and pressure distribution for given equilibrium velocities is obtained, with the finding that counter heat currents give rise to a pressure depression and a centripetal force. Second, it is shown that the ideal two-fluid hydro\-dynamics is simply an assembly of \textit{equilibrium conditions} -- expressions of entropy being maximal.