Phase diagram evolution at finite coupling in strong coupling lattice QCD

TL;DR

This paper analyzes the evolution of the phase diagram in strong coupling lattice QCD at finite temperature and density, incorporating finite coupling effects and NLO corrections to understand the chiral phase transition.

Contribution

It develops an analytic formulation including NLO effects in strong coupling lattice QCD, revealing how the phase diagram and critical point shift with coupling strength.

Findings

The ratio μ_c(T=0)/T_c(μ=0) increases with coupling strength.

The critical point moves to lower temperatures as coupling increases.

Partially chiral restored matter emerges due to interplay of order parameters.

Abstract

We investigate the chiral phase transition in the strong coupling lattice QCD at finite temperature and density with finite coupling effects. We adopt one species of staggered fermion, and develop an analytic formulation based on strong coupling and cluster expansions. We derive the effective potential as a function of two order parameters, the chiral condensate sigma and the quark number density $\rho_q$, in a self-consistent treatment of the next-to-leading order (NLO) effective action terms. NLO contributions lead to modifications of quark mass, chemical potential and the quark wave function renormalization factor. While the ratio mu_c(T=0)/Tc(mu=0) is too small in the strong coupling limit, it is found to increase as beta=2Nc/g^2 increases. The critical point is found to move in the lower T direction as beta increases. Since the vector interaction induced by $\rho_q$ is shown to grow as beta, the present trend is consistent with the results in Nambu-Jona-Lasinio models. The interplay between two order parameters leads to the existence of partially chiral restored matter, where effective chemical potential is automatically adjusted to the quark excitation energy.