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 temperature 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 Fisher zeros lie on the unit circle fnr Q > 1 and the number of such zeros increases with increasing e. The ferromagnetic and antiferromagnetic properties of the Ports model are investigated using the distribution of the Fisher zeros. For the Potts ferromagnet we verify the den Nijs formula for the thermal exponent gamma(1). For the Potts antiferromagnet we also verify the Baxter 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. All rights reserved.