Coulomb interaction at Superconductor to Mott-insulator transition

We reexamine the effects of long-range Coulomb interaction on the onset of superconductivity. We use the model of N complex scalar fields with the Coulomb interaction studied first by Fisher and Grinstein (FG). We find that near d=3 space dimension, the system undergoes second order phase transition if $N \ge 55.39$, but undergoes fluctuation driven first order transition if $N < 55.39$. We give the detailed derivation of the field theory Renormalization Group (RG) of this model to one loop. Our RG results disagree with those of FG at and near d=3. Possible scenario at d=2 is proposed.