INTERPLAY OF UNIVERSALITY CLASSES IN A 3-DIMENSIONAL YUKAWA MODEL

We investigate numerically on the lattice the interplay of universalit y classes of the three-dimensional Yukawa model with U(1) chiral symme try, using the Binder method of finite size scaling. At zero Yukawa co upling the scaling related to the magnetic Wilson-Fisher fixed point i s confirmed. At sufficiently strong Yukawa coupling the dominance of t he chiral fixed point associated with the 3D Gross-Neveu model is obse rved for various values of the coupling parameters, including infinite scalar self-coupling. In both cases the Binder method works consisten tly in a broad range of lattice sizes. However, when the Yukawa coupli ng is decreased the finite size behavior gets complicated and the Bind er method gives inconsistent results for different lattice sizes. This signals a crossover between the universality classes of the two fixed points.