Vacuum Fluctuations of a massless spin-1/2 field around multiple cosmic strings

TL;DR

This paper investigates how multiple cosmic strings influence vacuum fluctuations of a massless spinor field, revealing an attractive vacuum force between the strings due to their combined gravitational effects.

Contribution

It introduces a perturbative method to analyze vacuum fluctuations around multiple cosmic strings and identifies an additional energy contribution causing string attraction.

Findings

Multiple cosmic strings increase vacuum energy density

Vacuum fluctuations induce an attractive force between strings

The effect is additive with the number of strings

Abstract

We study the interaction of a massless quantized spinor field with the gravitational filed of N parallel static cosmic strings by using a perturbative approach. We show that the presence of more than one cosmic string gives rise to an additional contribution to the energy density of vacuum fluctuations, thereby leading to a vacuum force attraction between two parallel cosmic strings.