Neutrino energy equilibration models

Neutrino energy equilibration by neutrino-electron scattering is studied in four physical models, whose temperatures and densities are representative of stellar collapse conditions when electron scattering may be important. Results of Monte Carlo simulations are presented as data against which approximate transport methods may be tested. The neutrino thermalization rate is initially rapid and approximately exponential, and gradually decreases to a slow approach to equilibrium, suggesting the possibility of using a relaxation scheme to approximate the energy equilibration. However, when these results are compared with Fokker-Planck and thermal relaxation algorithms of the kind that have been widely employed in supernova calculations, substantial discrepancies are found.