Insights on the peak in the speed of sound of ultradense matter

TL;DR

This paper explores the physical mechanisms behind the peak in the speed of sound in ultradense matter, linking it to phase transitions involving chiral symmetry breaking and proposing a minimal model to explain this phenomenon.

Contribution

It identifies the minimal conditions for a speed of sound peak in ultradense matter and introduces a simple model based on symmetry breaking to explain this behavior.

Findings

A peak in the speed of sound naturally arises during chiral symmetry restoration.

A minimal model demonstrates the thermodynamic properties associated with this peak.

The mechanism could explain similar features observed in cold ultradense matter models.

Abstract

In this work we investigate the minimal physical requirements needed for generating a speed of sound that surpasses its asymptotic conformal limit. It is shown that a peak in the speed of sound of homogeneous matter naturally emerges in the transition from a phase with broken chiral symmetry to one with a gapped Fermi surface. We argue that this could be relevant for understanding the peak in the speed of sound displayed by some of the current models for cold ultradense matter. A minimal model implementation of this mechanism is presented, based on the spontaneous breakdown of an approximate particle-antiparticle symmetry, and its thermodynamic properties are determined.