Direct Urca processes on nucleons in cooling neutron stars

We use the field theoretical model to perform relativistic calculations of neutrino energy losses caused by the direct Urca processes on nucleons in the degenerate baryon matter. By our analysis, the direct neutron decay in the superdense nuclear matter under beta equilibrium is open only due to the isovector meson fields, which create a large energy gap between protons and neutrons in the medium. Our expression for the neutrino energy losses, obtained in the mean field approximation, incorporates the effects of nucleon recoil, parity violation, weak magnetism, and pseudoscalar interaction. For numerical testing of our formula, we use a self-consistent relativistic model of the multicomponent baryon matter. The relativistic emissivity of the direct Urca reactions is found substantially larger than predicted in the non-relativistic approach. We found that, due to weak magnetism effects, relativistic emissivities increase by approximately 40-50%, while the pseudoscalar interaction only slightly suppresses the energy losses, approximately by 5%.Comment: 21 pages, 2 figure

Plasma effects in neutrino-pair emission due to Cooper pairing of protons in superconducting neutron stars

The neutrino emission due to formation and breaking of Cooper pairs of protons in superconducting cores of neutron stars is considered with taking into account the electromagnetic coupling of protons to ambient electrons. Our calculation shows that the contribution of the vector weak current to the $\nu\bar\nu$ emissivity of protons is much larger than that calculated by different authors without taking into account the plasma effects. Partial contribution of the pairing protons to the total neutrino radiation from the neutron star core is very sensitive to the critical temperatures for the proton and neutron pairing and can dominate in some domains of these parameters.Comment: 5 pages, 4 figures, Contribution to the International Workshop ``HADRON PHYSICS 2002'', April 14 -- 19, Bento Goncalves, Rio Grande do Sul, Brazi

Weak magnetism effects in the direct Urca processes in cooling neutron stars

In the mean field approximation, we study the effects of weak magnetism and pseudoscalar interaction in the neutrino energy losses caused by the direct Urca processes on relativistic nucleons in the degenerate baryon matter. Our formula for the neutrino energy losses incorporates the effects of nucleon recoil, parity violation, weak magnetism, and pseudoscalar interaction. For numerical testing of our formula, we use a self-consistent relativistic model of the multicomponent baryon matter. We found that, due to weak magnetism effects, relativistic emissivities increase by approximately 40-50%, while the pseudoscalar interaction only slightly suppresses the energy losses, approximately by 5%.Comment: 11 pages,1 figur