NONEQUILIBRIUM NEUTRINO EMISSIVITIES AND OPACITIES OF NEUTRON-STAR MATTER

The neutrino emissivity of neutron star matter out of the beta-equilibrium is calculated. Such condition can prevail in a neutron star matter undergoing rapid compression. The formulae for the neutrino emissivity from direct and modified beta-processes are expressed in terms of the difference between the chemical potentials for the plasma composed of neutrons, protons, and electrons, delta-mu = mu(n) - mu(p) - mu(e). In the case when delta-mu (-delta-mu) is larger than kT, the nu(e)BAR emissivity is much larger (smaller) than the nu(e) one, with In(epsilon(nu-eBAR)/epsilon(nu-e)) approximately delta-mu/kT. Simultaneously, the absorption mean free path for nu(e)BAR is much longer (shorter) than for nu(e): In(lambda(a,nu-eBAR)/lambda(a,nu-e)) approximately delta-mu/kT.