Instability of cosmological event horizons of nonstatic global cosmic strings II: perturbations of gravitational waves and massless scalar field

TL;DR

This paper investigates the stability of cosmological event horizons of non-static global cosmic strings under gravitational and scalar perturbations, revealing their tendency to develop weak singularities or scalar singularities.

Contribution

It provides a detailed analysis of how gravitational waves and massless scalar fields affect the stability and nature of CEHs in non-static global cosmic strings.

Findings

Gravitational wave perturbations turn CEHs into weak spacetime singularities.

Scalar field perturbations can cause CEHs to become either weak or scalar singularities.

Test scalar field perturbations may not always accurately predict horizon stability.

Abstract

The stability of the cosmological event horizons (CEHs) of a class of non-static global cosmic strings is studied against perturbations of gravitational waves and massless scalar field. It is found that the perturbations of gravitational waves always turn the CEHs into non-scalar weak spacetime curvature singularities, while the ones of massless scalar field turn the CEHs either into non-scalar weak singularities or into scalar ones depending on the particular cases considered. The perturbations of test massless scalar field is also studied, and it is found that they do not always give the correct prediction.