Cosmic superfluidity: the evidence for superfluidity in neutron stars

Neutron stars are expected to be superfluid on quite general grounds. Following a brief historical review of theoretical calculations which have suggested the existence of at least three distinct superfluids inside neutron stars, the astrophysical evidence for their existence, which comes from the agreement between theory and observation for the observed relaxation of the rotation and spindown rates of the Vela and Crab pulsars, and of FSR 0525 + 21, following sudden jumps (glitches) in these quantities, is reviewed. The prospects for observing similar consequences of the pinned crustal neutron superfluid in the recently-discovered millisecond pulsars are examined. (author)