Instability of cosmological event horizons of nonstatic global cosmic strings. II. Perturbations of gravitational waves and massless scalar fields

Abstract

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