Superfluid 3He, Particle Physics and Cosmology

Superfluid 3He-A and high-temperature superconductors both have gapless fermionic quasiparticles with the "relativistic" spectrum close to the gap nodes. The interaction of these "relaitivistic" fermions with bosonic collective modes of the order parameter is described by the quantum field theory, which results in a close connection with particle physics. Many phenomena in high-energy physics and cosmology can thus be simulated in superfluid phases of 3He and in unconventional superconductors. This includes axial anomaly, vacuum polarization, zero-charge effect, fermionic charge of the vacuum, baryogenesis, event horizon, vacuum instability, Hawking radiation, etc. Analogs of some of these phenomena, which are related to the axial anomaly, have been experimentally simulated in superfluid 3He. This includes the baryogenesis by textures (Manchester), the baryogenesis by cosmic strings (Manchester) and the generation of the primordial magnetic field via the axial anomaly (Helsinki).