Multicanonical Spin Glass Simulations

We report a Monte Carlo simulation of the 2D Edwards-Anderson spin glass model within the recently introduced multicanonical ensemble. Replica on lattices of size L2 up to L = 48 are investigated. Once a true groundstate is found, we are able to give a lower bound on the number of statistically independent groundstates sampled. Temperature dependence of the energy, entropy and other quantities of interest are easily calculable. In particular we report the groundstate results. Computations involving the spin glass order parameter are more tedious. Our data indicate that the large L increase of the ergodicity time is reduced to an approximately V 3 power law. Altogether the results suggest that the multicanonical ensemble improves the situation of simulations for spin glasses and other systems which have to cope with similar problems of conflicting constraints. Supercomputer Computations Research Institute, Florida State University, Tallahassee, FL 32306, USA. Department of Physics, The Florida State University, Tallahassee, FL 32306, USA. On leave of absence from Department of Physics, Hacettepe University, Ankara, Turkey.