We investigate neutral current neutrino-nucleus interactions of interest in the supernova problem: endothermic and exothermic inelastic neutrino scattering processes; de-excitation of hot nuclei into neutrino pairs; and neutrino-antineutrino annihilation processes involving nuclei. We employ a shell model based treatment including allowed and forbidden transitions to compute the relevant weak strength distributions in nuclei. We discuss Fermi gas fitting formulae for the differential cross sections of all four processes for use in numerical stellar collapse calculations. Since target nuclei in stellar collapse are expected to be in highly excited states we explicitly include thermal effects in our calculations. We find that low-energy neutrino-pair production from hot nuclei and exothermic neutrino-nucleus scattering may have an important role in determining the evolution of the lepton distribution functions in the infalling presupernova core.

We investigate charged current neutrino and antineutrino capture on nuclei in the post-core bounce supernova environment. We point out that these processes may play an important, and heretofore overlooked, role in determining the nucleosynthesis in models of neutrino-heated supernova ejecta. In particular, we suggest that inclusion of these rates may help solve the problem in these models of overproduction of nuclides with neutron numbers near 50 and, in addition, enhance the production of the some of the light p-process nuclei in the α-process, particularly 92Mo. The neutrino capture rates on neutron-rich nuclei are found to be dominated by transitions to the Fermi (isobaric analog state) and Gamow-Teller resonances. In these cases, the neutrino capture thresholds are approximately just the nuclear Coulomb energy differences between nuclear parents and daughters, and the neutrino capture rates therefore exhibit only weak dependence on neutron and proton numbers compared to that of β--decay rates. We exploit this property to constrain the location of the r-process region in the post-core bounce supernova environment. We present analytic estimates for the rates of electron neutino and antineutrino capture on nuclei and nucleons.

We explore neutrino capture during [Formula Presented]-process nucleosynthesis in neutrino-driven ejecta from nascent neutron stars. We focus on the interplay between charged-current weak interactions and element synthesis, and we delineate the important role of equilibrium nuclear dynamics. During the period of coexistence of free nucleons and light and/or heavy nuclei, electron neutrino capture inhibits the [Formula Presented]-process. At all stages, capture on free neutrons has a larger impact than capture on nuclei. However, neutrino capture on heavy nuclei by itself, if it is very strong, is also detrimental to the [Formula Presented]-process until large nuclear equilibrium clusters break down and the classical neutron-capture phase of the [Formula Presented]-process begins. The sensitivity of the [Formula Presented]-process to neutrino irradiation means that neutrino-capture effects can strongly constrain the [Formula Presented]-process site, neutrino physics, or both. These results apply also to [Formula Presented]-process scenarios other than the neutrino-heated winds. © 1998 The American Physical Society.

The spectrum of nucleation-site separations in the cosmic QCD phase transition is calculated within the framework of homogeneous nucleation theory. This spectrum has the property that the ratio of the standard deviation of the separations to the mean separation has the constant value of 0.466, independent of any QCD physics parameters. When the assumption is made that a duality exists between nucleation sites and baryon fluctuation sites, the same spectrum may be applied to baryon-number fluctuation separations. When nucleosynthesis results are averaged over this spectrum, the upper limit on b(2.735KT0)3×(H050 km s-1Mpc-1)2, as derived from the observed upper limit to the primordial He4 abundance, drops from 0.8 to 0.56 in baryon inhomogeneous universes. In order for macroscopic baryon inhomogeneities to arise in the early Universe, persist to the era of nucleosynthesis, and give nucleosynthesis yields which allow b to be greater than the limit from standard big-bang nucleosynthesis, the QCD surface tension must be near its upper limit of around the cube of the coexistence temperature. © 1991 The American Physical Society.

We point out that a vμ or vτ neutrino with a cosmologically significant mass (10-100 eV) and a small mixing (vacuum mixing angle θ > 10-4) with a light ve would result in a matter-enhanced Mikheyev-Smirnov-Wolfenstein resonant transformation between these species in a region above the neutrino sphere but below the stalled shock during the reheating phase of a Type II supernova. The neutrino heating behind the shock is due to charged-current ve and v̄e captures. Since the vμ and vτ have considerably higher average energies than do the ve, neutrino flavor mixing would result in higher effective ve energies behind the shock and a concomitant increase in the heating rate. Our numerical calculations suggest that this effect results in a 60% increase in the supernova explosion energy, possibly helping to solve the energy problem of delayed-mechanism supernova models.

We suggest a new method for detection of neutrino bursts generated by distant supernovas in our galaxy and in the local group of galaxies. This new method is based on the detection of neutrons produced in the inelastic scattering of νμ and ντ neutrinos with nuclei via the neutral current channel. The advantages of such a detector are (1) the enhancement of neutrino scattering cross sections due to nuclear collective effects, (2) the selective detection of νμ and ντ supernova neutrinos, and (3) the existence of large geological deposits of suitable neutrino detector materials in nature. © 1990.