EXPERIMENTS WITH A GAUGE-INVARIANT ISING SYSTEM

Using Monte Carlo techniques, we evaluate the path integral for the four-dimensional lattice gauge theory with a Z2 gauge group. The system exhibits a first-order transition. This is contrary to the implications of the approximate Migdal recursion relations but consistant with mean-field-theory arguments. Our data" agree well with a low-temperature expansion and the exact duality between the high- and low-temperature phases. © 1979 The American Physical Society."