MONOPOLE PERCOLATION AND THE UNIVERSALITY CLASS OF THE CHIRAL TRANSITION IN 4-FLAVOR NONCOMPACT LATTICE QED

We simulate four-flavor noncompact lattice QED using the hybrid Monte Carlo algorithm on 10(4) and 16(4) lattices. Measurements of the monop ole susceptibility and the percolation order parameter indicate a tran sition at beta = 1/e2 = 0.205(5) with critical behavior in the univers ality class of four-dimensional percolation. We present accurate chira l condensate measurements and monitor finite-size effects carefully. T he chiral condensate data supports the existence of a power-law transi tion at beta = 0.205 in the same universality class as the chiral tran sition in the two-flavor model. The resulting equation of state predic ts the mass ratio m(pi)2/m(sigma)2 in good agreement with spectrum cal culations while the hypothesis of a logarithmically improved mean-fiel d theory fails qualitatively.