Avoiding closed timelike curves with a collapsing rotating null dust shell

TL;DR

This paper models a collapsing rotating null dust shell in flat space, showing it bounces before forming closed timelike curves, and proposes new definitions for the mass and angular momentum of the cosmic string.

Contribution

It introduces a simplified gravitational collapse model that prevents closed timelike curves and offers revised definitions for cosmic string parameters.

Findings

Shell bounces before CTC formation

Proposes new mass and angular momentum definitions

Model demonstrates avoidance of time travel paradoxes

Abstract

We present an idealised model of gravitational collapse, describing a collapsing rotating cylindrical shell of null dust in flat space, with the metric of a spinning cosmic string as the exterior. We find that the shell bounces before closed timelike curves can be formed. Our results also suggest slightly different definitions for the mass and angular momentum of the string.