Modified gravity with disappearing cosmological constant

TL;DR

This paper explores modified $f(R)$ gravity models that mimic a cosmological constant at large scales but allow for a vanishing cosmological constant in flat spacetime, with implications for local gravity tests and cosmic structure growth.

Contribution

It introduces new $f(R)$ models satisfying both cosmological and local constraints, and analyzes their effects on matter perturbations and growth rate evolution.

Findings

Models behave as $R-2\,\Lambda$ at high curvature.

Vanishing cosmological constant in flat spacetime.

Detectable deviations in matter perturbations from $\,\Lambda$CDM.

Abstract

New corrections to General Relativity are considered in the context of modified $f(R)$ gravity, that satisfy cosmological and local gravity constraints. The proposed models behave asymptotically as $R-2\Lambda$ at large curvature and show the vanishing of the cosmological constant at the flat spacetime limit. The chameleon mechanism and thin shell restrictions for local systems were analyzed, and bounds on the models were found. The steepness of the deviation parameter $m$ at late times leads to measurable signal of scalar-tensor regime in matter perturbations, that allows to detect departures form the $\Lambda$CDM model. The theoretical results for the evolution of the weighted growth rate $f\sigma_8(z)$, from the proposed models, were analyzed.