On de Sitter solutions in asymptotically safe $f(R)$ theories

TL;DR

This paper investigates the existence of de Sitter solutions in asymptotically safe $f(R)$ quantum gravity models, finding near de Sitter solutions in the UV but no real de Sitter solutions at small curvature, with implications for inflation.

Contribution

It provides a detailed analysis of de Sitter solutions in high-order $f(R)$ models of quantum gravity using resummation techniques, revealing near de Sitter solutions in the UV.

Findings

Near de Sitter solutions in the UV regime.

Absence of real de Sitter solutions at small curvature.

Detection of a convergence-limiting singularity in the complex plane.

Abstract

The availability of scaling solutions in renormalisation group improved versions of cosmology are investigated in the high-energy limit. We adopt $f(R)$-type models of quantum gravity which display an interacting ultraviolet fixed point at shortest distances. Expanding the gravitational fixed point action to very high order in the curvature scalar, we detect a convergence-limiting singularity in the complex field plane. Resummation techniques including Pad\'e approximants as well as infinite order approximations of the effective action are used to maximise the domain of validity. We find that the theory displays near de Sitter solutions as well as an anti-de Sitter solution in the UV whereas real de Sitter solutions, for small curvature, appear to be absent. The significance of our results for inflation, and implications for more general models of quantum gravity are discussed.