Complex-temperature phase diagrams for the q-state Potts model on self-dual families of graphs and the nature of the [formula presented] limit

Exact calculations of the Potts model partition function [formula presented] have been presented for arbitrary q and temperaturelike variable [formula presented] on self-dual strip graphs G of the square lattice with fixed width [formula presented] and arbitrarily great length [formula presented] with two types of boundary conditions. Letting [formula presented] the resultant free energy and complex-temperature phase diagram have been computed, including the locus B where the free energy is nonanalytic. Results are analyzed for widths [formula presented] These results have been used to study the approach to the large-q limit of [formula presented]