Reduction of Weak Interaction Rates in Neutron Stars by Nucleon Spin   Fluctuations: Degenerate Case
  Nucleon spin fluctuations in a dense medium reduce the ``naive'' values of weak interaction rates (neutrino opacities, neutrino emissivities). We extend previous studies of this effect to the degenerate case which is appropriate for neutron stars a few ten seconds after formation. If neutron-neutron interactions by a one-pion exchange potential are the dominant cause of neutron spin fluctuations, a perturbative calculation of weak interaction rates is justified for $T\alt 3m/(4\pi\alpha_\pi^2)\approx 1 MeV$, where $m$ is the neutron mass and $\alpha_\pi\approx15$ the pion fine-structure constant. At higher temperatures, the application of Landau's theory of Fermi liquids is no longer justified, i.e. the neutrons cannot be viewed as simple quasiparticles in any obvious sense. 
Georg Raffelt and Thomas Strobel (Max-Planck-Institut fur Physik,   Munich, Germany)