Instability of cosmological event horizons of nonstatic global cosmic strings

Abstract

The stability of the cosmological event horizons found recently by Gregory [Phys. Rev. D54, 4955 (1996)] for a class of non-static global cosmic strings is studied. It is shown that they are not stable to both test particles and physical perturbations. In particular, the back reaction of the perturbations of null dust fluids will turn them into spacetime singularities. The resulted singularities are strong in the sense that the distortion of test particles diverges logarithmically when these singular hypersurfaces are approaching.PACS numbers: 98.80.Cq, 04.20Jb, 04.40.+c.

Cylindrical systems in general relativity

“…In addition, gravitational radiation from cosmic strings and their instabilities were also studied in cylindrically symmetric spacetimes [17,23,25,27,87,164,249,323,324].…”

Inflation and nonsingular spacetimes of cosmic strings

“…But this metric still has a coordinate singularity (not a physical one). It was later questioned by Wang and Nogales [17] that this coordinate singularity is unstable to both test particles and physical perturbations. In particular, they argued that the back reaction of the perturbations of null dust fluids will turn the coordinate singularity into a physical one.…”

Spacetime structure of the global vortex

“…The resolution of the puzzle was of course to add time dependence to the vortex metric [11], which allowed for the existence of a non-singular solution to be demonstrated. This time dependence was of the same nature as that of the vacuum domain wall spacetime, i.e., a Hubble expansion along the length of the vortex, however, the full global spacetime structure of the global vortex and its maximal analytic extension was not explored, and indeed there have been claims that the cosmological event horizon present in the vortex spacetime is unstable to perturbations and becomes singular [12].…”