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

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.

Automated summary

In this study, we investigate the minimal physical requirements for generating a speed of sound that surpasses its asymptotic conformal limit, showing that a peak in the speed of sound emerges naturally in homogeneous matter during the transition from a phase with broken chiral symmetry to one with a gapped Fermi surface. A minimal model based on the spontaneous breakdown of an approximate particle-antiparticle symmetry is presented, and its thermodynamic properties are determined.