Motion of test particles and photons in the gravitational field of a cosmic string

Abstract

The motion of light rays and test particles are studied in the gravitational field of a cosmic string. Using Hiscock's semiclassical cosmic string metric, it is found that some of the outgoing particles will traverse an infinite distance but some particles may be trapped by the string at a finite distance from the axis. For incoming particles also, some will reach the boundary of the string but some may face a potential barrier and cannot penetrate beyond a certain distance from the string.