%0 Journal Article %T $ŠĆ$-Expansion of the Conductivity at the Superconductor-Mott Insulator Transition %A Rosario Fazio %A Dario Zappala` %J Physics %D 1995 %I arXiv %R 10.1103/PhysRevB.53.R8883 %X We study the critical behavior of the conductivity $\sigma(\omega)$ at the zero temperature superconductor-Mott insulator transition in $d$ space-time dimensions for a model of bosons with short-range interaction and no disorder. We obtain $\sigma(\omega_n ) = (4e^2/\hbar) \sigma_{\epsilon} \omega_n^{1-\epsilon}$, as predicted by the scaling theory, and the prefactor $\sigma_{\epsilon}$ is calculated in the $\epsilon$-expansion, to order $\epsilon ^2$ ($\epsilon = 4-d$). In two spatial dimensions, ($d=3$), we find a value of the universal conductance $\sigma^\star =0.315 (4e^2/h)$, in good agreement with the known Monte Carlo results. %U http://arxiv.org/abs/cond-mat/9511004v1