Defect formation in inhomogeneous 2-nd order phase transition: theory and experiment

The status quo in our understanding of defect formation during a rapid transition into the broken symmetry state in condensed matter and cosmology is discussed. An observation of vortex nucleation in neutron absorption experiments in superfluid 3He-B is interpreted in terms of defect formation during inhomogeneous cooling through T_c. Due to the temperature gradient in the locally heated region the superfluid phase transition occurs as a propagating front. The theoretical considerations of vortex formation at the propagating front are based on work by Kibble-Volovik, Kopnin-Thuneberg, and Aranson-Kopnin-Vinokur.