19th International Conference on QCD in Extreme Conditions (XQCD 2023)

The QCD chiral phase transition for various numbers of flavors at imaginary baryon chemical potential

26 Jul 2023, 18:00

2h

Floor D Foyer

Poster Poster session

Speaker

Reinhold Kaiser

Description

In order to constrain the QCD phase diagram with physical quark masses, the QCD chiral phase transition in the massless limit is investigated, although this is a challenging problem for lattice QCD. In 1984, Pisarski and Wilczek predicted a first-order transition for $N_{\text{f}}\ge 3$, based on RG investigations of a linear sigma model in three dimensions, which was supported by lattice QCD simulations on coarse lattices. However, recent lattice QCD results from our group provide strong evidence for a second order chiral phase transition for $N_{\text{f}}=2-6$ massless quark flavors. It was demonstrated that the first-order chiral transitions, observed on coarse lattices, terminate at a tricritical lattice spacing, and are thus not connected to the continuum chiral limit. As a consequence, the chiral transition in the continuum is of second order, as it is always approached from a crossover region. Adopting the same strategy, we investigate the nature of the chiral phase transition as a function of the number of quark flavors and the lattice spacing for a fixed imaginary baryon chemical potential. We find that first-order transitions, observed on coarse lattices, disappear towards the continuum limit, which coincides with the situation at zero density.