There are several classes of homogeneous Fermi systems that are characterized by the topology of the energy spectrum of fermionic quasiparticles: (ⅰ) gapless systems with a Fermi surface, (ⅱ) systems with a gap in their spectrum, (ⅲ) gapless systems with topologically stable point nodes (Fermi points), and (ⅳ) gapless systems with topologically unstable lines of nodes (Fermi lines). Superfluid ~3He-A and electroweak vacuum belong to the universality class 3. The fermionic quasiparticles (particles) in this class are chiral: they are left-handed or right-handed. The collective bosonic modes of systems of class 3 are the effective gauge and gravitational fields. The great advantage of superfluid ~3He-A is that we can perform experiments by using this condensed matter and thereby simulate many phenomena in high energy physics, including axial anomaly, baryoproduction, and magnetogenesis. ~3He-A textures induce a nontrivial effective metrics of the space, where the free quasiparticles move along geodesics. With ~3He-A one can simulate event horizons, Hawking radiation, rotating vacuum, etc. High-temperature superconductors are believed to belong to class 4. They have gapless fermionic quasiparticles with a "relativistic" spectrum close to gap nodes, which allows application of ideas developed for superfluid ~3He-A.
展开▼
