Comment on Asymptotically Safe Inflation

TL;DR

This paper critiques the feasibility of asymptotically safe inflation, arguing that the inflationary energy scale is too low to reach the ultraviolet fixed point, requiring fine-tuning for sufficient inflation.

Contribution

It provides an analysis of the RG flow in asymptotically safe gravity during inflation, highlighting limitations and the need for fine-tuning.

Findings

Inflation energy scale is too low to approach the fixed point.

Fine-tuning is necessary for sufficient e-folds.

RG flow from fixed point to IR reproduces current cosmological constants.

Abstract

We comment on Weinberg's interesting analysis of asymptotically safe inflation (arXiv:0911.3165). We find that even if the gravity theory exhibits an ultraviolet fixed point, the energy scale during inflation is way too low to drive the theory close to the fixed point value. We choose the specific renormalization groupflow away from the fixed point towards the infrared region that reproduces the Newton's constant and today's cosmological constant. We follow this RG flow path to scales below the Planck scale to study the stability of the inflationary scenario. Again, we find that some fine tuning is necessary to get enough efolds of infflation in the asymptotically safe inflationary scenario.