  The influence of gapless dissipative degrees of freedom on the
superconductor-insulator transition in two dimensions is investigated. We
develop a series expansion for the free energy of a (2+1)-dimensional XY model
coupled to a bosonic heat bath that can be approximately summed to all orders.
The calculation explicitly conserves topological excitations. We derive the
zero temperature phase diagram and the free energy critical exponent, and find
a transition from universal to non-universal scaling behavior as the coupling
to the dissipative environment is increased, implying the existence of a new
universality class.
