Constraining the QCD phase diagram by tricritical lines at imaginary chemical potential

TL;DR

This paper uses lattice QCD simulations to identify tricritical points at imaginary chemical potential, revealing how these points influence the phase transition behavior at real chemical potential and constraining the QCD phase diagram.

Contribution

It provides the first clear evidence of tricritical points in the QCD phase diagram at imaginary chemical potential, elucidating their role in the deconfinement transition.

Findings

Identified two tricritical points in the (T,m) phase diagram at imaginary chemical potential.

Demonstrated that the shape of the deconfinement critical line is governed by tricritical scaling.

Showed that the deconfinement transition weakens with increasing real chemical potential.

Abstract

We present unambiguous evidence from lattice simulations of QCD with three degenerate quark species for two tricritical points in the (T,m) phase diagram at fixed imaginary \mu/T=i\pi/3 mod 2\pi/3, one in the light and one in the heavy mass regime. These represent the boundaries of the chiral and deconfinement critical lines continued to imaginary chemical potential, respectively. It is demonstrated that the shape of the deconfinement critical line for real chemical potentials is dictated by tricritical scaling and implies the weakening of the deconfinement transition with real chemical potential. The generalization to non-degenerate and light quark masses is discussed.