Neutrinos in gravitational collapse. I. Analysis of trajectories

Abstract

The behavior of neutrinos is investigated in a collapsing object. The model considered consists of the Friedmann dust interior matched onto the Schwarzschild exterior. The neutrino trajectories are taken to be null geodesics, the geometric optics approximation being valid for the relevant energy range. The matter is assumed to be transparent to the neutrinos. The null geodesics are first computed in both geometries appropriately matched at the boundary. An expression is then derived for the spectral shifts of the neutrino. The properties of backward emission and the confinement of the neutrinos to the vicinity of the collapsing object at various stages of collapse are studied in detail. The analysis leads to a rather interesting and complex pattern in the evolution of the process of confinement as the collapse progresses.