Chiral symmetry restoration of QCD and the Gross-Neveu model
  Two flavour massless QCD has a second order chiral transition which has been argued to belong to the universality class of the $3d$ O(4) spin model. The arguments have been questioned recently, and the transition was claimed to be mean field behaved. We discuss this issue at the example of the $3d$ Gross-Neveu model. A solution is obtained by applying various well established analytical methods. 
T.Reisz (Institute of Theoretical Physics, University of Heidelberg,   Germany)