TRANSFER-MATRIX FOR THE RESTRICTED CANONICAL AND MICROCANONICAL ENSEMBLES

The numerical transfer matrix for the partition function of discrete l attice models is generalized to allow the calculation of the density o f states Omega(E), and the restricted density of states Omega(E,M). Gi ven Omega(E,M) the partition function is expressed as a polynomial in the variables x=e(beta h) and y=e(-beta). These algorithms are illustr ated with calculations for the Ising model on finite square lattices. The zeros of the partition function are examined in both the complex x and y planes. Finite size scaling analysis of the zeros leads to very accurate estimates for the critical temperature and critical exponent s.