Chiral condensate in neutron matter

TL;DR

This paper extends chiral perturbation theory calculations of the in-medium quark condensate to neutron-rich matter, finding minimal deviations from linear density behavior and implications for chiral symmetry restoration in neutron stars.

Contribution

It provides the first detailed analysis of the quark condensate in pure neutron matter using chiral perturbation theory, highlighting differences from symmetric nuclear matter.

Findings

Small deviations from linear density approximation in neutron matter

Reduced impact of 2π-exchange mechanisms in neutron-rich environments

Chiral symmetry restoration tendencies are enhanced in neutron-rich systems

Abstract

A recent chiral perturbation theory calculation of the in-medium quark condensate $<\bar q q>$ is extended to the isospin-asymmetric case of pure neutron matter. In contrast to the behavior in isospin-symmetric nuclear matter we find only small deviations from the linear density approximation. This feature originates primarily from the reduced weight factors (e.g. 1/6 for the dominant contributions) of the $2\pi$-exchange mechanisms in pure neutron matter. Our result suggests therefore that the tendencies for chiral symmetry restoration are actually favored in systems with large neutron excess (e.g. neutron stars). We also analyze the behavior of the density-dependent quark condensate $<\bar q q>(\rho_n)$ in the chiral limit $m_\pi\to 0$.