The problem of repulsive quark interactions – Lattice versus mean field models

Abstract

We calculate the 2nd and 4th order quark number susceptibilities at zero baryochemical potential, using a PNJL approach and an approach which includes, in a single model, quark and hadronic degrees of freedom. We observe that the susceptibilities are very sensitive to possible quark–quark vector interactions. Compared to lattice data our results suggest that above Tc any mean field type of repulsive vector interaction can be excluded from model calculations. Below Tc our results show only very weak sensitivity on the strength of the quark and hadronic vector interaction. The best description of lattice data around Tc is obtained for a case of coexistence of hadronic and quark degrees of freedom.