Sound modes in holographic superfluids

TL;DR

This paper explores the behavior of sound modes in superfluids, comparing relativistic and non-relativistic cases through hydrodynamics and holographic models, revealing temperature-dependent sound speed variations.

Contribution

It introduces a holographic model to compute multiple sound speeds in superfluids and compares relativistic results with classical predictions, highlighting differences at low temperatures.

Findings

Relativistic second sound speeds differ from Landau's non-relativistic predictions.

Computed first, second, and fourth sound speeds as functions of temperature.

Identified temperature-dependent variations in sound modes within holographic superfluids.

Abstract

Superfluids support many different types of sound waves. We investigate the relation between the sound waves in a relativistic and a non-relativistic superfluid by using hydrodynamics to calculate the various sound speeds. Then, using a particular holographic scalar gravity realization of a strongly interacting superfluid, we compute first, second and fourth sound speeds as a function of the temperature. The relativistic low temperature results for second sound differ from Landau's well known prediction for the non-relativistic, incompressible case.