The chiral phase transition from strong to weak coupling

TL;DR

This paper investigates how the nature of the chiral phase transition in lattice QCD changes from strong to weak coupling, revealing a non-monotonic behavior of the transition order as lattice spacing varies.

Contribution

It demonstrates the weakening of the chiral transition at coarser lattices for multiple flavors, connecting strong coupling results with continuum behavior.

Findings

Transition weakens significantly from $N_{\tau}=4$ to $N_{\tau}=2$ for $N_f=4,8$

Results suggest a second-order transition in the strong coupling limit for $N_f=4$

Critical meson mass behavior is non-monotonic with lattice spacing.

Abstract

The order of the chiral phase transition of lattice QCD with unimproved staggered fermions is known to depend on the number of quark flavours, their masses and the lattice spacing. Previous studies in the literature for $N_f \in \{ 3,4 \}$ show first-order transitions, which weaken with decreasing lattice spacing. Here we investigate what happens when lattices are made coarser to establish contact to the strong coupling region. For $N_f \in \{4,8 \}$ we find a drastic weakening of the transition when going from $N_{\tau}=4$ to $N_{\tau}=2$, which is consistent with a second-order chiral transition reported in the literature for $N_f=4$ in the strong coupling limit. This implies a non-monotonic behaviour of the critical quark or pseudo-scalar meson mass, which separates first-order transitions from crossover behaviour, as a function of lattice spacing.