Short - range nucleon correlations and neutrino emission by neutron stars at low temperatures

We argue that the strong interaction between protons and neutrons in the asymmetric liquid (neutron star) distorts strongly proton Fermi surface. We use the Feynman diagram approach to calculate probability of triple (e-p-n) short range correlations in terms of the short range (p-n) correlations and ultrarelativistic Coulomb (p-e) interaction. We find that these correlations lead to holes in (e-p-n) Fermi seas and remove Pauli blocking of direct neutron decay. This results in the instability of the zero temperature neutron stars due to the radiation of neutrinos and antineutrinos. As a result, an isolated neutron star should collapse to a new phase with a lifetime ∼ 109 years for nuclear matter density. This lifetime due to β decay should decrease as ∝ ρ−3 for higher matter densities. The presence of the short-range p-n correlations leads to significant neutrino cooling of cold neutron stars at nonzero temperature and all values of p/n ratio though in the Landau Fermi liquid approach no direct neutron decay could occur for p/n ≪ 0.1. As a result, we predict the existence of almost invisible neutron stars. We also predict significantly shorter lifetime and faster neutrino cooling of hyperon stars.