Neutrino Production and Transport during Gravitational Collapse

Citation

Bond, John Richard (1979) Neutrino Production and Transport during Gravitational Collapse. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/mty2-sm41. https://resolver.caltech.edu/CaltechTHESIS:10062016-102636623

Abstract

The P-N method is developed to describe the transport of neutrinos in collapsing stellar cores, and the multigroup flux limited diffusion and equilibrium diffusion approximations are obtained from it. An effective Lagrangian for weak neutral and charged current neutrino interactions which is applicable to low energy neutrino processes is derived. The neutrino source functions which enter into the P-N equations are given a many body theory formulation in terms of weak current-current correlation functions. Within this framework, we deal, in turn, with the scattering reactions νA → νA, νA → νA*, νN → νN (both for non-degenerate and degenerate nucleons), νe → νe, and νν → νν, and the production and absorption reactions e^-p ⇄ nν_e, e⁺n ⇄ pν̅_e, e^-AZ ⇄ A(Z-1) ν_e, e⁺e^- ⇄ νν̅, and γ_pℓ ⇄ νν̅. These equations are then applied to the various phases of neutrino flow during iron core collapse: the transparent stage to the onset of trapping; the approach of electron neutrinos to beta-equilibrium; the evolution of the muon neutrino and antineutrino distribution functions towards the Fermi-Dirac form; the conditions under which ν_µ ν̅_µ radiative energy loss exceeds the ν_e loss; comparison of the P-1 and flux limited diffusion methods of spatial transport in a static pre-bounce core.

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