Partition function zeros of the Q-state Potts model for non-integer Q

The distribution of the zeros of the partition function in the complex temp erature plane (Fisher zeros) of the two-dimensional Q-state Ports model is studied for non-integer Q. On L x L self-dual lattices studied (L less than or equal to 8). no Fisher zero lies on the unit circle p(0) = e(10) in the complex p = (e(beta J) - 1) root Q plane for Q < 1, while some of the Fish er zeros lie on the unit circle fnr Q > 1 and the number of such zeros incr eases with increasing e. The ferromagnetic and antiferromagnetic properties of the Ports model are investigated using the distribution of the Fisher z eros. For the Potts ferromagnet we verify the den Nijs formula for the ther mal exponent gamma(1). For the Potts antiferromagnet we also verify the Bax ter conjecture for the critical temperature and present new results for the thermal exponents in the range 0 < Q < 3. (C) 2000 Elsevier Science B.V. A ll rights reserved.