Remarks on vacuum fluctuations around a spinning cosmic string

TL;DR

This paper investigates vacuum fluctuations near a spinning cosmic string using point-splitting, revealing that common Green functions can produce unphysical results despite satisfying standard equations.

Contribution

It demonstrates that the standard Green function approach yields pathological results in a spinning cosmic string background, emphasizing the need for careful renormalization.

Findings

Standard Green functions can lead to unphysical results in this context

Renormalization by removing Minkowski contribution is essential

The point-splitting method effectively analyzes vacuum fluctuations

Abstract

We apply the point-splitting method to investigate vacuum fluctuations in the nonglobally hyperbolic background of a spinning cosmic string. Implementing renormalization by removing the Minkowski contribution it is shown that although the Green function in the literature satisfies the usual Green function equation, it leads to pathological physical results.