Towards a possible solution to the Hubble tension with Horndeski gravity

TL;DR

This paper proposes a Horndeski gravity-based dark energy model that can potentially resolve the Hubble tension by exhibiting unique dynamical features and fitting well with low-redshift observational data.

Contribution

It introduces a novel scalar-tensor dark energy scenario within Horndeski gravity that alleviates the Hubble tension and is free from instabilities.

Findings

Model exhibits phantom behavior at low redshifts.

Model fits observational data well, reducing Hubble tension.

Model remains free from gradient and ghost instabilities.

Abstract

The Hubble tension refers to the discrepancy in the value of the Hubble constant $H_0$ inferred from the cosmic microwave background observations, assuming the concordance $\Lambda$CDM model of the Universe, and that from the distance ladder and other direct measurements. In order to alleviate this tension, we construct a plausible dark energy scenario, within the framework of Horndeski gravity which is one of the most general scalar-tensor theories yielding second-order equations. In our set-up, we include the self-interactions and nonminimal coupling of the dynamical dark energy scalar field which enable very interesting dynamics leading to a phantom behaviour at low redshifts along with negative dark energy densities at high redshifts. These two features together make this model a promising scenario to alleviate the Hubble tension for appropriate choices of the model parameters. Towards a consistent model building, we show that this set-up is also free from both the gradient and ghost instabilities. Finally, we confront the predictions of the model with low redshift observations from Pantheon, SH0ES, cosmic chronometers and BAO, to obtain best fit constraints on model parameters.