Low-Energy Quantum Effective Action for Relativistic Superfluids

TL;DR

This paper derives the low-energy effective action for relativistic superfluids with spontaneously broken U(1) symmetry, showing it is governed by the equation of state and analyzing corrections at high densities.

Contribution

It provides a formal derivation of the superfluid Goldstone boson effective action using quantum effective action formalism, including leading and higher-order corrections.

Findings

Effective action determined by the equation of state.

Leading order effective action at high densities derived.

Higher-order terms appear at alpha_s^2 with known coefficients.

Abstract

We consider relativistic superfluids where the U(1) baryon symmetry is spontaneously broken. Using the formalism of the quantum effective action, we show that the low-energy dynamics of the superfluid Goldstone boson is completely determined by the equation of state. Applying the general formalism to asymptotically high densities, we find the effective action for the superfluid Goldstone field to leading order in alpha_s, and show that terms containing fifth and higher powers of the Goldstone boson appear only at the alpha_s^2 level with known coefficients.