Cosmic String Lensing and Closed Time-like Curves

TL;DR

This paper analyzes gravitational lensing by relativistic cosmic strings and argues that the formation of closed time-like curves is generally unstable due to particle interactions, with implications for cosmic string physics.

Contribution

It demonstrates that closed time-like curves around cosmic strings are unstable in realistic conditions, highlighting the impact of particles and motion on gravitational lensing effects.

Findings

Closed time-like curves are unstable in the presence of particles.

Gravitational lensing by moving cosmic strings is enhanced by their motion.

Single particles can prevent the formation of closed time-like curves.

Abstract

In an analysis of the gravitational lensing by two relativistic cosmic strings, we argue that the formation of closed time-like curves proposed by Gott is unstable in the presence of particles (e.g. the cosmic microwave background radiation). Due to the attractor-like behavior of the closed time-like curve, we argue that this instability is very generic. A single graviton or photon in the vicinity, no matter how soft, is sufficient to bend the strings and prevent the formation of closed time-like curves. We also show that the gravitational lensing due to a moving cosmic string is enhanced by its motion, not suppressed.