Statistics – Applications
Scientific paper
Jan 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996phdt.........9m&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF CALIFORNIA, SAN DIEGO, 1996.Source: Dissertation Abstracts International, Volume: 57-06, Section:
Statistics
Applications
Scientific paper
Two types of stellar physics are studied: the stability of supermassive stars and weak interactions in the post-core-bounce supernova. Applications to nucleosynthesis issues are discussed. The stability of nonrotating supermassive stars in the presence of a small dark matter component is examined. It is found that the destabilizing effects of first order nonlinear corrections from general relativity can be neutralized by a significant amount of nonrelativistic dark matter. It is possible for supermassive stars to be stabilized through the hydrogen burning stage, where significant mass loss might result in the ejection of the nucleosynthesis products of hot hydrogen burning. The process of electron neutrino and electron antineutrino capture on nuclei with masses A>40 in the context of the post-core-bounce supernova environment is examined. The influence of final state electron blocking, extended distributions of Gamow-Teller strength, the Coulomb wave correction and other factors is discussed. The strength of forbidden capture channels is estimated and their importance in neutrino capture rate estimates is discussed. Tables and formulas for calculating these rates, in the context of the post-core-bounce supernova environment are presented. The electron fraction (or neutron-to-proton ratio) in the post-core-bounce supernova environment is examined. This quantity is important for determining nucleosynthesis in models of neutrino-heated supernova ejecta. In particular, the existence of the r-process and p-process nuclei as well as the overproduced N = 50 nuclei depends on the exact value of the electron fraction during nucleosynthesis. Factors which establish the neutron-to-proton ratio, such as the charged current weak interactions, weak freeze out and "alpha freeze out" are examined. Of particular importance are the (anti)neutrino spectra, both in their deviation from an approximate blackbody spectrum and in their time history. The possibility that neutrino capture on heavy nuclei competes with beta decay in the r-process environment is considered. It is found that neutrino capture is not excluded by measurements of existing abundances. In fact, assuming the presence of an intense neutrino flux actually provides a better fit to steady weak flow for the N = 82 elements.
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