First order signatures in 4D pure compact U(1) gauge theory with toroidal and spherical topologies

We study the pure compact U(1) gauge theory with the extended Wilson action (beta, gamma couplings) by finite size scaling techniques, in lattices ranging from L = 6 lu L = 24 in the region of gamma less than or equal to 0 with toroidal and spherical topologies. The phase transition presents a double peak structure which survives in the thermodynamical limit in the torus. In the sphere the evidence supports the idea of a weaker, but still first order, phase transition. For gamma < 0 the transition becomes weaker and larger lattices are needed to find its asymptotic behaviour. Along the transient region the behaviour is the typical one of a weak first order transition for both topologies, with a region where 1/d < v < 0.5, which becomes nu approximate to 1/4 when larger lattices are used. (C) 1998 Elsevier Science B.V.