The U(1) phase transition on toroidal and spherical lattices
  We have studied the properties of the phase transition in the U(1) compact pure gauge model paying special atention to the influence of the topology of the boundary conditions. From the behavior of the energy cumulants and the observation of an effective \nu -> 1/d on toroidal and spherical lattices, we conclude that the transition is first order. 
Isabel Campos, Andres Cruz and Alfonso Tarancon