Dense matter in a holographic hard-wall model of QCD

TL;DR

This paper uses a holographic hard-wall model to explore dense QCD matter, revealing a baryonic phase with high density and implications for neutron star properties, including maximum mass predictions.

Contribution

It introduces a holographic approach to model dense QCD matter with a focus on baryonic phases and neutron star applications, incorporating IR boundary effects.

Findings

Baryonic matter phase appears at high baryon density.

Maximum neutron star mass exceeds two solar masses.

Equation of state derived from the model supports neutron star mass predictions.

Abstract

A deeper understanding of QCD matter at strong coupling remains challenging due to its non-perturbative nature. To this end, we study a two-flavor holographic hard-wall model to investigate the properties of QCD at finite-density and zero temperature with a nonvanishing quark mass. A dense matter phase is described by a classical solution of the equations of motion in a homogeneous Ansatz. We apply holographic renormalization to formulate the holographic dictionary that relates UV boundary data in the bulk with the physical quantities in QCD. We emphasize a role played by an IR boundary action on the hard-wall when analyzing the QCD phase structures in this holographic setup. It is found that a baryonic matter phase is manifested in this model with a high baryon number density and a nearly vanishing chiral condensate. We derive the equation of state for the resulting phase and use it to work out the mass-radius relation for neutron stars. We find that the maximum mass of neutron stars can exceed two solar masses for a wide range of free parameters in this model. We also comment on an alternative scenario about the phase structure such that the baryonic matter phase arises at a baryon number chemical potential greater than a critical value.