The three-dimensional Thirring model for N-f=4 and N-f=6

We present Monte Carlo simulation results for the three-dimensional Thirrin g model for numbers of fermion flavours N-f = 4 and 6. For N-f = 4 we find a second-order chiral symmetry breaking transition at strong coupling, corr esponding to an ultra-violet fixed point of the renormalisation group defin ing a non-trivial continuum limit. The critical exponents extracted from a fit to a model equation of state are distinct from those found for N-f = 2. For N-f = 6, in contrast, we present evidence for tunnelling between chira lly symmetric and broken vacua at strong coupling, implying that the phase transition is first-order and no continuum limit exists. The implications f or the phase diagram of the model in the plane of coupling strength and Nr are briefly discussed. (C) 1999 Elsevier Science B.V. All rights reserved.