Nuclear thermodynamics and the in-medium chiral condensate

TL;DR

This paper studies how the chiral condensate in nuclear matter changes with temperature and density using chiral effective field theory, showing that chiral symmetry remains broken up to 100 MeV and twice nuclear saturation density.

Contribution

It provides a systematic, realistic calculation of the temperature and density dependence of the chiral condensate including multi-pion exchanges and three-body correlations.

Findings

Chiral symmetry remains broken up to 100 MeV and twice nuclear saturation density.

Nuclear liquid-gas phase transition influences the chiral condensate at low temperatures.

The framework includes detailed many-body interactions up to three loops.

Abstract

The temperature dependence of the chiral condensate in isospin-symmetric nuclear matter at varying baryon density is investigated using thermal in-medium chiral effective field theory. This framework provides a realistic approach to the thermodynamics of the correlated nuclear many-body system and permits calculating systematically the pion-mass dependence of the free energy per particle. One- and two-pion exchange processes, $\Delta(1232)$-isobar excitations, Pauli blocking corrections and three-body correlations are treated up to and including three loops in the expansion of the free energy density. It is found that nuclear matter remains in the Nambu-Goldstone phase with spontaneously broken chiral symmetry in the temperature range $T\lesssim 100\,$MeV and at baryon densities at least up to about twice the density of normal nuclear matter, $2\rho_0 \simeq 0.3\, $fm$^{-3}$. Effects of the nuclear liquid-gas phase transition on the chiral condensate at low temperatures are also discussed.