BOUNDARY EFFECTS IN THE 3-DIMENSIONAL ISING-MODEL

Simulations of the standard three-dimensional Ising model with a varie ty of boundary conditions, for medium and large systems, are compared with field-theoretical predictions. In particular, setting boundary sp ins equal to zero is not the best approximation for the Dirichlet boun dary condition of zero magnetization at the boundary. The simulations for the specific heat agree semiquantitatively with the field theory f or periodic and Dirichlet boundary conditions.