Application of the path optimization method to the sign problem in an effective model of QCD with a repulsive vector-type interaction

Abstract

The path optimization method is applied to a QCD effective model with a Polyakov loop and a repulsive vector-type interaction at finite temperature and density to circumvent the model sign problem. We show how the path optimization method can increase the average phase factor and control the model sign problem. This is the first study which correctly treats the repulsive vector-type interaction in the QCD effective model with a Polyakov loop via the Markov-chain Monte Carlo approach. It is shown that we can evade the model sign problem within the standard path-integral formulation by complexifying the temporal component of the gluon field and the vector-type auxiliary field.