title: Superfluid density of an open dissipative condensate.
abstract: I calculate the superfluid density of a nonequilibrium steady state condensate of particles with finite lifetime. Despite the absence of a simple Landau critical velocity, a superfluid response survives, but dissipation reduces the superfluid fraction. I also suggest an idea for how the superfluid density of an example of such a system, i.e., microcavity polaritons, might be measured.
authors.affiliation: SUPA, School of Physics and Astronomy, University of St. Andrews, KY16 9SS, United Kingdom.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Keeling