Chiral limit of strongly coupled lattice gauge theories

We construct a new and efficient cluster algorithm for updating strongly coupled U(N) lattice gauge theories with staggered fermions in the chiral limit. The algorithm uses the constrained monomer-dimer representation of the theory and should also be of interest to researchers working on other models with similar constraints. Using the new algorithm we address questions related to the chiral limit of strongly coupled U(N) gauge theories beyond the mean field approximation. We show that the infinite volume chiral condensate is non-zero in three and four dimensions. However, on a square lattice of size L we find Sigma(x) <(ψ) over bar psi(x)(ψ) over bar psi(0)> similar to L2-eta for large L where eta = 0.420(3)/N + 0.078(4)/N-2. These results differ from an earlier conclusion obtained using a different algorithm. Here we argue that the earlier calculations were misleading due to uncontrolled autocorrelation times encountered by the previous algorithm. (C) 2003 Elsevier Science B.V. All rights reserved.