Quantum fluctuation of stress tensor in a higher-derivative scalar field theory around a cosmic string

TL;DR

This paper computes the quantum vacuum fluctuations of the stress tensor in a higher-derivative scalar field theory around a cosmic string, revealing no reduction near the conical singularity unlike simpler models.

Contribution

It applies a method to derive the stress tensor from the effective action for higher-derivative theories, showing the behavior differs from non-higher-derivative cases.

Findings

Quantum stress tensor expressed as a sum of free massive scalar contributions

No reduction of stress tensor values near the conical singularity

Distinct behavior compared to scalar field squared vacuum expectation

Abstract

We calculate the vacuum fluctuation of the stress tensor of a higher-derivative theory around a thin cosmic string. To this end, we adopt the method to obtain the stress tensor from the effective action developed by Gibbons et al. By their method, the quantum stress tensor of higher-derivative scalar theories without self-interaction is expressed as a simple sum of quantum stress tensors of free massive scalar fields. Unlike the vacuum expectation value of the scalar field squared obtained in the similar model, there appears no reduction of the values near the conical singularity.