Supernova Explosion and Neutrino Degeneracy in the Core

Abstract

Diffusion of neutrinos in supernova core is investigated on the base of neutral current theory of weak interaction. The core becomes opaque to neutrinos before electron captures of nuclei proceed sufficiently so that the number of leptons in the core can never be decreased rapidly, but it is conserved at high densities (p^>10^<12> g/cm^3 ). We have obtained the following results. 1) Neutrinos are strongly degenerate in the core and Fermi energy at p = 10^<14> g/cm^3 exceeds 120MeV if the number ratio of leptons to baryons confined in the core n_L/n_B &gnsim; 0.35. 2) Neutralization of the collapsing matter proceeds so slowly compared with the case of neglecting neutrino degeneracy that lepton pressure is always higher than that of nuclear matter up to nuclear density if n_L/n_B &gnsim; 0.18. 3) As the result of 2), the bounce of collapsing core becomes more possible. Duration of neutrino degeneracy is about ten seconds and sufficiently long for bounce. Diffusion of degenerate neutrinos is also discussed.