William R. Yueh

Neutrino processes in dense matter

Expressions for the source and collision terms of the neutrino transport equation relevant to the neutrino transport supernova model are derived in the framework of the theory of neutral currents. In particular we study the capture and emission of neutrini (and anti-neutrini) by free nucleos, the inelastic scattering by free nucleons, the coherent scattering by nuclei, as well as the corresponding muonic processes.We also derive an analytical formula for the neutrino scatteringrate on electrons, valid for large electron degeneracy.

Scattering functions for neutrino transport

We derive an expression for the scattering functions for electron-neutrino and electronanti-neutrino Compton scattering in a form suitable for a numerical solution of the neutrino transfer equations. An analytical expression is given for the case of large electron degeneracy. The modification due to possible neutral currents is discussed.

Compton scattering opacity

Abstract We show first that there is an error in the literature in the evaluation of the Compton scattering opacity; second, we compare the corrected values with the published ones and, third, we show that two commonly made approximations are inaccurate in the case of electron degeneracy.

Neutrino transport in supernova models: A multigroup, flux limited diffusion scheme

A multigroup, diffusion scheme is derived from the Boltzmann equation for efficient numerical computation of neutrino transport in a collapsing stellar core. This scheme treats all neutrino scattering processes correctly with a Legendre expansion of the scattering rates. Modifications of the diffusion coefficient and the addition of a flux limiter extend the applicability of the scheme to neutrino transparent regimes and improve the agreement of the solution in both opaque and transparent regimes with those obtained analytically for some test problems. In addition, a more accurate treatment of the neutrino flowAcross shock discontinuities is developed through a shock matching condition. The solutions given by this multigroup, flux-limited diffusion scheme are compared with those of a modifiedSNcode.

Shock structure and neutrino radiation in stellar collapse

Neutrino transport through a shock front in the context of a collapsing stellar core is carefully considered. We show (1) that the neutrino transport produces negligible shock broadening and that the shock width is therefore microscopic; and (2) that numerical stellar collapse calculations using a pseudoviscosity can thus seriously underestimate the neutrino flux across the shock unless unusually fine zoning is used in the shock region. This increased neutrino flux should yield the soughtfor stress necessary to produce a supernova explosion.

The effects of Fermi statistics on neutrino transport in supernova models

The neutrino Boltzmann transport equation is solved numerically and neutrino-electron Compton scattering is handled accurately. It is shown that a correct treatment of the (Fermi) statistics in the scattering of neutrinos essentially closes the low-energy window over a large fraction of the core. The low-energy occupation probabilities of the neutrinos are found to be very sensitive to a proper handling of the Pauli inhibition terms, whereas the stress on and the energy transfer to matter are not sensitive to it.

Scattering of light by light; Prospects for high order interactions with relatively low thresholds

Abstract Spontaneous pair production processes by the action of classical, slowly varying electromagnetic fields associated with intense, focused laser beams are considered. The threshold for pair production and light-light scattering under identical experimental conditions are then compared. In view of the relatively low thresholds predicted for these interactions, attention is drawn to the interesting possibility of producing monopole pairs in such focused laser beams taking into account the final state interactions.