Effects of modified gravity on the turnaround radius in cosmology

TL;DR

This paper explores how modified gravity theories affect the cosmological turnaround radius, providing a way to constrain or rule out certain models based on deviations from Einstein's theory.

Contribution

It extends the definition and analysis of the turnaround radius to a broader class of gravity theories, including quantum R^2 gravity, beyond scalar-tensor and F(R) models.

Findings

Deviations in the turnaround radius can constrain model parameters.

A deviation of more than 10% could rule out some theories.

The study provides a method to test gravity theories using cosmological data.

Abstract

We revisit the concept of turnaround radius in cosmology, in the context of modified gravity. While preliminary analyses were limited to scalar-tensor/$F(R)$ gravity, we extend the definition and the study of this quantity to a much broader class of theories including also quantum $R^2$ gravity. The turnaround radius is computed in terms of the parameters of the theory and it is shown that a deviation not larger than 10\% of this quantity from its value in Einstein's theory could constrain the model parameters and even rule out some current theories.