Lepton loss and entropy generation in stellar collapse

Stellar core collapse is studied with the aim of understanding how sensitive the properties of the core are to variations in the underlying physical and astronomical assumptions made. A homogeneous core model is employed and the collapse is studied from the termination of core Si burning until neutrino trapping and beta equilibrium are attained. This corresponds to evolution from central densities of approximately 10 to the 9th g/cu cm to 10 to the 13th g/cu cm. It is found that the properties of the core important for the later stages of the collapse, the entropy and lepton fraction, are remarkably insensitive to most variations of the assumptions about the input physics, collapse rate and initial conditions.