NEW METHOD TO DETERMINE 1ST-ORDER TRANSITION POINTS FROM FINITE-SIZE DATA

We consider a temperature-driven first-order phase transition describing the coexistence of q ordered low-temperature phases and one disordered high-temperature phase at the infinite-volume transition temperature T0. Analyzing the exponential corrections to the periodic partition function in a box of volume V, Z(per) = SIGMA(m) exp(-beta-f(m)V), where f(m) is the (metastable) free energy of the phase m, we propose several definitions of a finite-volume transition temperature To(V) which involve only exponential corrections with respect to T0. We test our propositions in the d = 2 Potts model for q = 5, 8, and 10 by means of Monte Carlo simulations, using the single-cluster update procedure.