SERIES STUDIES OF THE 4-STATE POTTS MODEL

The four-state Potts model is studied via series expansions. Free energy and susceptibility high-temperature series are calculated for hypercubic lattices of general dimensionality. Estimates of critical temperatures and critical indices gamma and alpha are obtained as functions of dimensionality. The free energy, magnetisation, and susceptibility low-temperature series are calculated for d=4. The high-and low-temperature series together indicate that the phase transition in this dimensionality is first order. From this result the authors suggest that the apparent second-order transitions shown by the susceptibility for d>or=4 might be explained as spinodal pseudotransitions.