Search

Hot and dense astrophysical environments such as the early universe, core collapse novae and binary neutron star mergers generate dense neutrino gases which can sub- sequently have an important effect on processes which occur in these environments. In this thesis we will present the results from several numerical simulations of these gases particularly in cases which are relevant to core collapse supernovae. These simulations employ fewer imposed spatial symmetries than those used in earlier works, and provide insight into behavior which may be expected to occur in three key regions of the explosion. We observe that when the neutrino gas develops fine scale spatial structure an equilibration of the flavor content also obtains on average. We also observe that when flavor conversion develops in regions of low neutrino number density, the gas does not display the development of fine scale spatial structure, and instead a spectral split is obtained similarly to more symmetric simulations. Finally, at high number densities, the gas forms dynamic flavor oscillation waves which can redistribute and transport the electron lepton number content of the gas.

The ANtarctic Impulsive Transient Antenna (ANITA) searches for ultra high energyneutrinos interacting in the Antarctic ice cap. It is a long duration balloon experimentcomposed of an array of broadband dual-polarized horn antennas that had itsfirst science flight over Antarctica in December 2006 through January 2007. ANITArelies upon the Askaryan effect, in which a particle shower in a dense medium emitscoherent Cherenkov radiation at radio wavelengths, for the detection of a neutrinoinduced shower. Using the null result reported elsewhere of the detection of neutrinocandidates by the ANITA-I experiment, we place a limit upon the flux of neutrinosfrom Gamma Ray Bursts (GRBs). During the ANITA-I flight, 21 GRBs were detectedby spacecraft, but none occurred in the primary ANITA field of view while the instrumentwas operating. Using the measured redshifts of the limited number of localizedGRBs that occurred during the flight, we model their neutrino flux using a basicWaxman-Bahcall model. We are able to place a 90% CL limit on the E-4 promptneutrino fluence from GRB061222B in the energy range of 107.7 GeV ≤ εν ≤ 109.7 GeVof εν4Φν ≤ 4.65x1018 GeV3 cm-2 at a ratio of 4.81x107 to the predicted model for aburst time of 42 seconds. With no neutrino detections over the entire ANITA-I flight,lasting over 17 days, we set a limit with a 90% CL on a E-4 flux over the energyrange of 107.65 GeV ≤ εν ≤ 1010 GeV of εν4Φν ≤ 6.5x1010 GeV3 cm-2 s-1 sr-1.