Ghost-free non-local $F(R)$ Gravity Compatible with ACT

TL;DR

This paper tests ghost-free non-local $F(R)$ gravity models against recent cosmological data, demonstrating their compatibility with observational constraints from ACT, Planck, and BICEP, and exploring their theoretical properties.

Contribution

It introduces a ghost-free non-local $F(R)$ gravity framework, derives de Sitter solutions, and shows compatibility of specific models with current cosmological observations.

Findings

Both power-law and $R^2$ models fit observational constraints.

The theory can be expressed as an $F(R,\phi)$ gravity model.

De Sitter solutions are realizable within this framework.

Abstract

We confront the ghost-free non-local $F(R)$ gravity theories with the latest Atacama Cosmology Telescope (ACT) constraints on the spectral index of the scalar perturbations and the updated constraints of Planck/BICEP on the tensor-to-scalar ratio. After reviewing how the ghost-free non-local version of $F(R)$ gravity can be obtained, we show that the de Sitter solution can be obtained in this framework. Also, we show that the resulting theory can be cast in terms of an $F(R,\phi)$ theory of gravity. We analyze two models of non-local $F(R)$ gravity, one power-law and the $R^2$ model, and we show that both models can be compatible with the ACT and updated Planck/BICEP constraints.