Chiral phase transition of QCD with $N_f=2+1$ flavors from holography

TL;DR

This paper uses a modified holographic QCD model to study the chiral phase transition in three-flavor QCD, revealing the dependence on quark masses and identifying different transition types and universality classes.

Contribution

It introduces a modified soft-wall holographic model to analyze the quark mass dependence of the chiral phase transition in N_f=2+1 QCD, aligning with lattice results.

Findings

First order transition near chiral limit

Crossover at large quark masses

Distinct universality classes for different transition regions

Abstract

Chiral phase transition for three-flavor $N_f=2+1$ QCD with $m_u=m_d\neq m_s$ is investigated in a modified soft-wall holographic QCD model. Solving temperature dependent chiral condensates from equations of motion of the modified soft-wall model, we extract the quark mass dependence of the order of chiral phase transition in the case of $N_f=2+1$, and the result is in agreement with the "Colombia Plot", which is summarized from lattice simulations and other non-perturbative methods. First order phase transition is observed around the three flavor chiral limit $m_{u/d}=0, m_{s}=0$, while at sufficient large quark masses it turns to be a crossover phase transition. The first order and crossover regions are separated by a second order phase transition line. The second order line is divided into two parts by the $m_{u/d}=m_s$ line, and the $m_s$ dependence of the transition temperature in these two parts are totally contrast, which might indicate that the two parts are governed by different universality classes.