Cosmology, particle physics, and superfluid 3He

Many direct parallels connect superfluid He-3 with the field theories describing the physical vacuum, gauge fields and elementary fermions. Superfluid He-3 exhibits a variety of topological defects which can be detected with single-defect sensitivity. Modern scenarios of defect-mediated baryogenesis can be simulated by the interaction of the He-3 vortices and domain walls with fermionic quasiparticles. Formation of defects in a symmetry-breaking phase transition in the early Universe, which could be responsible for large-scale structure formation and for microwave-background anisotropy, also may be modelled in the laboratory. This is supported by the recent observation of vortex formation in neutron-irradiated He-3-B where the ''primordial fireball'' is formed in an exothermic nuclear reaction.