Universal conductivity of dirty bosons at the superconductor-insulator transition

The superconductor-insulator transition at zero temperature in two dimensions is studied by Monte Carlo simulations of interacting bosons (Cooper pairs) moving in a quenched random potential. We calculate the universal conductivity {sigma}{sup *} and the critical exponents at the superconductor-insulator transition. For the short-range repulsive case we find {sigma}{sup *}=(0.14{plus minus}0.03){sigma}{sub {ital Q}}, where {sigma}{sub {ital Q}}{sup {minus}1}=={ital R}{sub {ital Q}} =={ital h}/(2{ital e}){sup 2}{congruent}6.45{ital k}{Omega}, and for long-range Coulomb interactions we find {sigma}{sup *}=(0.55{plus minus}0.1){sigma}{sub {ital Q}}.