Quench-induced vortices in the symmetry-broken phase of liquid He

Motivated by the study of cosmological phase transitions, our understanding of the formation of topological defects during spontaneous symmetry breaking and the associated non-equilibrium field theory has recently changed. Experiments have been performed in superfluid to test the new ideas involved. In particular, it has been observed that a vortex density is seen immediately after pressure quenches from just below the transition. We discuss possible interpretations of these vortices, conclude they are consistent with our ideas of vortex formation and propose a modification of the original experiments.