Effects of the anomaly on the QCD chiral phase transition

Abstract

We study a lattice field theory described by two flavors of mass less staggered fermions interacting with U(1) gauge fields in the strong coupling limit. We show that the lat tice model has a SU(2) × SU(2) × U(1) chiral symmetry and can be used to model the two-flavor QCD chi ral phase transition in the absence of the anomaly. It is also possible to add a coupling to this model which breaks the chiral symmetry to SU(2) × SU(2) and thus mimics the effects of the anomaly in two-flavor QCD. We construct an efficient directed loop alg orithm to study such a model. We show that the chiral phase transition in our model is first ord er in the absence of the anomaly, while it becomes second order with O(4) exponents when the anomaly is turned on.