Physics
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........16g&link_type=abstract
PhD Dissertation, California Univ. Davis, CA United States
Physics
Quantum Chromodynamics, Gravitational Collapse, Supernovae, Hydrodynamics, Explosions, Viscosity, Shock Waves, Matter (Physics), Quarks, Gluons, Baryons, Plasmas (Physics), Conductive Heat Transfer, Hadrons
Scientific paper
Results are presented for numerical calculations of gravitational collapses and explosions. Two effects are studied. The first involves aspects of the numerical models used in almost all current gravitational collapse calculations. The second involves phase transitions in the equation of state of dense matter. A (1+1) dimensional general relativistic hydrodynamics code was constructed to investigate both effects. A modification of standard artificial viscosity methods was developed. This extended both the tensor artificial viscosity formulation and the artificial heat conduction formulation to the general relativistic regime. This method shows better results for collapse calculations than the standard scalar artificial viscosity. Numerical collapse calculations were also examined with respect to the number of zones used in the model. These calculations suggest that the number of zones used in current supernova calculations may be insufficient, and that the more sophisticated artificial viscosity methods used may be useful in future core collapse investigations. The second effect studied by this thesis is the impact of phase transitions in dense matter on the results of core collapse in Type 2 supernovae. Two different phase transitions were investigated. The QCD phase transition embodies the prediction of quantum chromodynamics that at high density the constituents of baryonic matter will be free quarks and gluons. The effects on the shock wave formed by core collapse and bounce is studied for various phase transitions. We find that some of the phase transitions modeled significantly increase the shock strength. The second phase transition we study is one from a normal hadronic gas to Q matter. Q matter is a phase of dense baryonic matter that is motivated by soliton models for the nucleus. It has been used to model zero temperature dense matter in static stellar objects, here we extend it to finite temperature, determine the phase transitions with hadronic matter, and apply it to collapse calculations. The phase transitions we find are different than those of the quark-gluon plasma, they resemble an explosion, with a sudden increase in the pressure and temperature. We find that some phase transitions significantly increase the severity of core bounce explosions.
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