Addressing Cosmological Tensions by Non-Local Gravity

TL;DR

This paper reviews non-local gravity models inspired by quantum theory as potential solutions to cosmological tensions like the Hubble and growth rate discrepancies, highlighting promising features and challenges such as the need for screening mechanisms.

Contribution

It introduces and analyzes two non-local gravity models, demonstrating their potential to address key cosmological tensions and comparing their effects on structure growth and lensing.

Findings

Lowered growth of structures in the phenomenological model

Equivalent background expansion to ΛCDM in the phenomenological model

Potential to alleviate H0 and σ8 tensions with the Noether symmetry-based model

Abstract

Alternative cosmological models have been under deep scrutiny in recent years, aiming to address the main shortcomings of the $\Lambda$CDM model. Moreover, as the accuracy of cosmological surveys improved, new tensions have risen between the model-dependent analysis of the Cosmic Microwave Background and lower redshift probes. Within this framework, we review two quantum-inspired non-locally extended theories of gravity, whose main cosmological feature is a geometrically driven accelerated expansion. The models are especially investigated in light of the Hubble and growth tension, and promising features emerge for the Deser--Woodard one. On the one hand, the cosmological analysis of the phenomenological formulation of the model shows a lowered growth of structures but an equivalent background with respect to $\Lambda$CDM. On the other hand, the study of the lensing features at the galaxy cluster scale of a new formulation of non-local cosmology, based on Noether symmetries, makes room for the possibility of alleviating both the $H_0$ and $\sigma_8$ tension. However, the urgent need for a screening mechanism arises for this non-local theory of gravity.