On ion-ion correlation effects during stellar core collapse

¹ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str.1, Postfach 1317, 85741 Garching, GermanyMax-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany e-mail: thj@mpa-garching.mpg.de
² Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München, Germany
³ CITA, University of Toronto, Toronto, Ontario M5S 3H8, Canada

Received: 13 April 2005
Accepted: 19 June 2005

Abstract

The role of ion-ion correlations in suppressing neutrino-nucleus elastic scattering during stellar core collapse is reinvestigated, using two different equations of state. We test the improved description by Itoh et al. against the treatment suggested by Horowitz and find that the stronger cross-section reduction for small momentum transfer in the former case does not lead to noticeable changes of the core deleptonization and entropy increase during collapse, because the improvements are relevant below neutrino trapping conditions only for very low neutrino energies, corresponding to a very small phase-space volume. Treating screening effects for ionic mixtures by the linear mixing rule applied to the collection of representative heavy nucleus, α particles, and free nucleons, which is assumed to characterize the composition in nuclear statistical equilibrium, we cannot determine mentionable differences during stellar collapse, because α particles are not sufficiently abundant, and their coherent scattering opacity is too small.