The (2+1)-dimensional Gross-Neveu model with a U (1) chiral symmetry at nonzero temperature

We present results from numerical simulations of the (2 + 1) dimensional Gross-Niveu model with a U(1) chiral symmetry and N-f = 4 fermion at nonzero temperature. We provide evidence that there are two different chirally symmetric phases, one critical and one with finite correlation length, separated by a Berezinskii-Kosterlitz-Thouless transition. We have also identified a regime above the critical temperature in which the fermions acquire a screening mass even in the absence of chiral symmetry breaking, analogous to the pseudogap behaviour observed in cuprate superconductors. (C) 2001 Published by Elsevier Science B.V.