The three-dimensional, three-state Potts model in an external field

We analyze the critical behaviour of the 3-d, 3-state Potts model in the presence of an external ordering field. From a finite size scaling analysis on lattices of size up to 70(3) we determine the critical endpoint of the line of first order phase transitions as (beta(c),h(c)) = (0.54938(2),0.000775(10)). We determine the relevant temperature like and symmetry breaking directions at this second order critical point and explicitly verify that it is in the universality class of the 3-d Ising model. (C) 2000 Elsevier Science B.V. All rights reserved.