Ray trajectories for a spinning cosmic string and a manifestation of self-cloaking

TL;DR

This paper investigates how light rays behave around a spinning cosmic string using a Tamm medium model, revealing unique cloaking and evanescent wave phenomena related to the string's rotation.

Contribution

It introduces a geometric-optics analysis of a Tamm medium representing a spinning cosmic string, highlighting novel cloaking effects and wave behaviors.

Findings

Rays do not cross the string boundary.

Evanescent waves exist in regions supporting closed timelike curves.

Spinning strings are slightly visible, non-spinning strings are nearly invisible.

Abstract

A study of ray trajectories was undertaken for the Tamm medium which represents the spacetime of a cosmic spinning string, under the geometric-optics approximation. Our numerical studies revealed that: (i) rays never cross the string's boundary; (ii) the Tamm medium supports evanescent waves in regions of phase space that correspond to those regions of the string's spacetime which could support closed timelike curves; and (iii) a spinning string can be slightly visible while a non-spinning string is almost perfectly invisible.