Phase structure of two-color QCD at real and imaginary chemical potentials; lattice simulations and model analyses

摘要

We investigate the phase structure of two-color QCD at both real andimaginary chemical potentials mu, performing lattice simulations and analyzingthe data with the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model.Lattice QCD simulations are done on an 8^3 times 4 lattice with theclover-improved two-flavor Wilson fermion action and the renormalization-groupimproved Iwasaki gauge action. We test the analytic continuation of physicalquantities from imaginary mu to real mu by comparing lattice QCD resultscalculated at real mu with the result of analytic function the coefficients ofwhich are determined from lattice QCD results at imaginary mu. We also test thevalidity of the PNJL model by comparing model results with lattice QCD ones.The PNJL model is good in the deconfinement region, but less accurate in thetransition and confinement regions. This problem is improved by introducing thebaryon degree of freedom to the model. It is also found that the vector-typefour-quark interaction is necessary to explain lattice data on the quark numberdensity.