First evidence that non-metricity f(Q) gravity could challenge $\Lambda$CDM

TL;DR

This paper introduces a new $f(Q)$ gravity model that challenges the $ ext{Lambda}$CDM paradigm, showing it can fit observational data slightly better without early dark energy features or conflicting Newton's constant variations.

Contribution

The paper presents a novel $f(Q)$ gravity model that differs from $ ext{Lambda}$CDM and fits cosmological data comparably or slightly better, without requiring $ ext{Lambda}$CDM as a limit.

Findings

Model slightly preferred over $ ext{Lambda}$CDM in some datasets based on information criteria.

Model passes BBN constraints and observational bounds on Newton's constant variation.

No early dark energy features in the proposed model.

Abstract

We propose a novel model in the framework of $f(Q)$ gravity, which is a gravitational modification class arising from the incorporation of non-metricity. The model has General Relativity as a particular limit, it has the same number of free parameters to those of $\Lambda$CDM, however at a cosmological framework it gives rise to a scenario that does not have $\Lambda$CDM as a limit. Nevertheless, confrontation with observations at both background and perturbation levels, namely with Supernovae type Ia (SNIa), Baryonic Acoustic Oscillations (BAO), cosmic chronometers (CC), and Redshift Space Distortion (RSD) data, reveals that the scenario, according to AIC, BIC and DIC information criteria, is in some datasets slightly preferred comparing to $\Lambda$CDM cosmology, although in all cases the two models are statistically indiscriminate. Finally, the model does not exhibit early dark energy features, and thus it immediately passes BBN constraints, while the variation of the effective Newton's constant lies well inside the observational bounds.