Perturbations in higher derivative gravity beyond maximally symmetric spacetimes
Abstract
We study (covariant) scalarvectortensor (SVT) perturbations of infinite derivative gravity (IDG), at the quadratic level of the action, around conformallyflat, covariantly constant curvature backgrounds which are not maximally symmetric spacetimes (MSS). This extends a previous analysis of perturbations done around MSS, which were shown to be ghostfree. We motivate our choice of backgrounds which arise as solutions of IDG in the UV, avoiding big bang and black hole singularities. Contrary to MSS, in this paper we show that, generically, all SVT modes are coupled to each other at the quadratic level of the action. We consider simple examples of the full IDG action, and illustrate this mixing and also a case where the action can be diagonalized and ghostfree solutions constructed. Our study is widely applicable for both nonsingular cosmology and black hole physics where backgrounds depart from MSS. In appendices, we provide SVT perturbations around conformallyflat and arbitrary backgrounds which can serve as a compendium of useful results when studying SVT perturbations of various higher derivative gravity models.
 Publication:

arXiv eprints
 Pub Date:
 May 2019
 arXiv:
 arXiv:1905.03227
 Bibcode:
 2019arXiv190503227S
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory
 EPrint:
 36 pages, 1 figure