Dynamical stability of Minkowski space in higher order gravity

TL;DR

This paper analyzes the stability of Minkowski space in various higher order gravity theories using a dynamical systems approach, providing conditions for stability and a method applicable to multiple models.

Contribution

It introduces a dynamical system method to assess Minkowski stability in modified gravity theories, including $f(R)$, $f(R)+ ext{higher order}$, and scalar-tensor models, with new stability criteria.

Findings

Minkowski space is asymptotically stable in ghost-free $f(R)$ theories.

Stability conditions for higher order gravity with $ ext{R} abla^2 R$ corrections are established.

Scalar-tensor models with non-minimal kinetic coupling also exhibit Minkowski stability.

Abstract

We discuss the Minkowski stability problem in modified gravity by using dynamical system approach. The method to investigate dynamical stability of Minkowski space was proposed. This method was applied for some modified gravity theories, such as $f(R)$ gravity, $f(R)+\alpha R\Box R$ gravity and scalar-tensor gravity models with non-minimal kinetic coupling. It was shown that in the case of $f(R)$ gravity Minkowski solution asymptotically stable in ghost-free ($f'>0$) and tachyon-free ($f">0$) theories in expanding Universe with respect to isotropic and basic anisotropic perturbations. In the case of higher order gravity with $\alpha R\Box R$ correction conditions of Minkowski stability with respect to isotropic perturbations significantly different: $f'(0)<0$, $f"(0)<0$ and $3f'(0)+f"(0)^2/\alpha>0$. And in the case of scalar-tensor gravity with non-minimal kinetic coupling Minkowski solution asymptotically stable in expanding Universe with respect to isotropic perturbations of metric. Moreover the developed method may be used for finding additional restrictions on parameters of different modified gravity theories.