NUCLEAR IN-MEDIUM EFFECTS AND NEUTRINO EMISSIVITY OF NEUTRON-STARS

The influence of nuclear in-medium effects on the neutrino emissivity of neutron star matter is studied within a thermodynamic T-matrix appr oach. It is shown that, depending on temperature, density and total mo mentum, the in-medium scattering cross-section of the nucleons can be significantly altered compared to the free-scattering cross-section. I n particular, as a result of the blocking of intermediate states the e ffective nucleon-nucleon cross-section is considerably enhanced for tr ansferred momenta of about twice the Fermi momentum, and diminished at low momentum transfers. The impact of these in-medium effects on the neutrino emissivity of the modified Urea and the neutron-neutron brems strahlung processes is considered. The modifications of the neutrino t hermal conductivity and of the neutrino mean free path are also discus sed.