PHASES AND TRIVIALITY OF SCALAR QUANTUM ELECTRODYNAMICS

The phase diagram and critical behavior of scalar quantum electrodynamics are investigated using lattice gauge theory techniques. The lattice action fixes the length of the scalar ("Higgs") field and treats the gauge field as noncompact. The phase diagram is two dimensional. No fine-tuning or extrapolations are needed to study the theory's critical behavior. Two lines of second-order phase transitions are discovered and the scaling laws for each are studied by finite-size scaling methods on lattices ranging from 64 through 244. One line corresponds to monopole percolation and the other to a transition between a "Higgs" and a "Coulomb" phase, labeled by divergent specific heats. The lines of transitions cross in the interior of the phase diagram and appear to the unrelated. The monopole percolation transition has critical indices which are compatible with ordinary four-dimensional percolation uneffected by interactions. Finite-size scaling and histogram methods reveal that the specific heats on the "Higgs-Coulomb" transition line are well fit by the hypothesis that scalar quantum electrodynamics is logarithmically trivial. The logarithms are measured in both finite-size scaling of the specific heat peaks as a function of volume as well as in the coupling constant dependence of the specific heats measured on fixed but large lattices. The theory is seen to be qualitatively similar to λφ4 theory. The standard Cray random number generator ranf proved to be inadequate for the 164 lattice is simulation. This failure and our "work-around" solution are briefly discussed. © 1995 The American Physical Society.