Primordial neutron star; a new candidate of dark matter

Abstract

Z-boson exchange interaction induces attractive force between left-handed neutrino and neutron. The Ginzburg-Landau mean field calculation and the Bogoliubov transformation suggest that this attractive force leads to neutrino-neutron pair condensate and super-fluidity. When the result of super-fluid formation is applied to the early universe, horizon scale pair condensate may become a component of dark energy. A further accretion of other fermions from thermal cosmic medium gives a seed of primordial neutron stars made of proton, neutron, electron, and neutrino in beta-equilibrium. Primordial neutron stars may provide a mechanism of giving a part or the whole of the dark matter in the present universe, if a properly chosen small fraction of cosmic thermal particles condenses to neutrino-neutron super-fluid and primordial neutron star not to over-close the universe. The proposal can be verified in principle by measuring neutrino burst at primordial neutron star formation and by detecting super-fluid relic neutrinos in atomic experiments at laboratories.