Instabilities and Particle Production in S-Brane Geometries

TL;DR

This paper analyzes the classical stability of S-brane geometries with cosmological horizons, revealing their instability due to infinite radiation flux and demonstrating thermal particle production with Hawking temperature, suggesting horizon singularity formation.

Contribution

It provides a detailed analysis of the instability of S-brane horizons and computes the thermal particle production spectrum, linking it to Hawking radiation.

Findings

Horizons in S-brane geometries are unstable to perturbations.

Observers crossing the horizon encounter infinite radiation flux.

Particle production spectrum is thermal with Hawking temperature.

Abstract

We study the classical stability of a class of S-brane geometries having cosmological horizons. By considering the perturbations of the metric in these geometries we establish that their horizons are unstable in the sense that an observer trying to cross the horizon experiences an infinite flux of radiation at the instant of crossing. The backreaction of this radiation is likely to convert the horizons into curvature singularities, similar to the instability of the internal Cauchy horizon of the Reissner-Nordstrom black hole. We also compute the particle production by the time-dependent fields in the future regions of these geometries, and find that the spectrum of produced particles is thermal, with temperature coinciding with the Hawking temperature computed by euclideanizing the metric in the static region. Possible implications of these results are discussed.