A Simple Model of Entropy Generation and Deleptonization in Collapsing Stellar Cores

A simple model incorporating the essential physics of core collapse is formulated. The model accurately reproduces the behavior during infall of the entropy and the electron and lepton fractions exhibited by the central zones of large-scale numerical models. Being free from any ambiguities associated with the results of complex numerical calculations, the model clearly shows that extensive entropy production and lepton loss accompany the infall stellar cores, whether they are initially warm or cold. The implication is that the prompt ejection of matter by the shock generated at core bounce is highly unlikely for any plausible precollapse core structure.