1208.2283 (Kouji Kashiwa et al.)

Two-color QCD at imaginary chemical potential and its impact on real
chemical potential    [PDF]

Kouji Kashiwa, Takahiro Sasaki, Hiroaki Kouno, Masanobu Yahiro

We study properties of two-color QCD at imaginary chemical potential ($\mu$) from the view point of the Roberge-Weiss (RW) periodicity, the charge conjugation and the pseudo-reality. At $\mu=i\pi T/2$, where $T$ is temperature, the system has both the ${\mathbb Z}_{2}$ and the charge-conjugation symmetry. The two symmetries are preserved at lower $T$, but simultaneously broken at higher $T$. The Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model has the same properties as two-color QCD for the RW periodicity, the charge conjugation and the pseudo-reality. The nontrivial correlation between the chiral and ${\mathbb Z}_{2}$ symmetry breakings are investigated by introducing the entanglement vertex in the PNJL model. The order of the ${\mathbb Z}_{2}$ symmetry breaking at the RW endpoint is the second order when the correlation is weak, but becomes the first order when the correlation is strong. We also investigate the impact of the correlation on the phase diagram at real $\mu$.

View original: http://arxiv.org/abs/1208.2283