Radiation flux and spectrum in the Vaidya collapse model

TL;DR

This paper analyzes quantum radiation in a collapsing Vaidya spacetime, showing divergence of flux at the Cauchy horizon and non-thermal spectra when a naked singularity forms, extending previous dust cloud results.

Contribution

It demonstrates divergence of radiation flux and non-thermal spectra in Vaidya collapse, generalizing earlier findings from dust cloud models.

Findings

Radiation flux diverges at the Cauchy horizon.

Spectrum becomes non-thermal near naked singularities.

Results extend previous dust cloud models.

Abstract

We consider the quantization of a massless scalar field, using the geometric optics approximation, in the background spacetime of a collapsing spherical self-similar Vaidya star, which forms a black hole or a naked singularity. We show that the outgoing radiation flux of the quantized scalar field diverges on the Cauchy horizon. The spectrum of the produced scalar partcles is non-thermal when the background develops a naked singularity. These results are analogous to those obtained for the scalar quantization on a self-similar dust cloud.