Spinning strings, cosmic dislocations and chronology protection

TL;DR

This paper investigates quantum field behavior around spinning cosmic strings with dislocations, showing that back reaction may prevent the formation of closed timelike curves, thus supporting chronology protection.

Contribution

It provides a detailed analysis of quantum fluctuations near spinning strings with dislocations and proposes a mechanism for horizon formation that safeguards causality.

Findings

Mean-square field fluctuation remains finite during CTC formation

Vacuum energy diverges, indicating a subtle back reaction effect

Horizon formation potentially prevents the emergence of CTCs

Abstract

A massless scalar field is quantized in the background of a spinning string with cosmic dislocation. By increasing the spin density toward the dislocation parameter, a region containing closed timelike curves (CTCs) eventually forms around the defect. Correspondingly, the propagator tends to the ordinary cosmic string propagator, leading therefore to a mean-square field fluctuation, which remains well behaved throughout the process, unlike the vacuum expectation value of the energy-momentum tensor, which diverges due to a subtle mechanism. These results suggest that back reaction leads to the formation of a "horizon" that protects from the appearance of CTCs.