The early Universe is believed to have undergone a sequence of very rapid phase transitions. Defect formation in these transitions has been suggested as the source for the anisotropy in the cosmic background radiation and the large-scale structure in the distribution of visible mass. So far controlled laboratory experiments have not been performed on homogeneous second order phase transitions as a function of transition speed and a freeze-out of topological defects has not been convincingly demonstrated. Recently a new phenomenon was discovered in rotating superfluid 3He-B: the formation of quantized vortices within bulk superflow in the presence of ionizing radiation. This ``mini bang'' allows one to explore the superfluid transition within the clean bulk medium on the microsecond time scale. The experiment appears to provide the first quantitative test of the theories on defect formation in a time-dependent second order phase transition. This is one example among several analogies, such as baryogenesis or generation of primordial magnetic fields, where quantized vortices and other defects in the 3He superfluids provide a connection to quantum field theory and its applications to cosmology.
PACS: 67.57.Fg, 05.70.Fh, 98.80.Cq.
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