Alleviating $H_0$ and $S_8$ Tensions Simultaneously in K-essence Cosmology

TL;DR

This paper explores a K-essence cosmological model with a linear coupling that can simultaneously reduce the tensions in Hubble constant and structure growth measurements, aligning early and late-Universe observations.

Contribution

It introduces a specific K-essence model with a linear coupling that fits inflationary data and alleviates the $H_0$ and $S_8$ tensions simultaneously.

Findings

Inflationary parameters compatible with BICEP/Keck data.

Model reduces $H_0$ tension to about 2.2 sigma.

Model diminishes $S_8$ discrepancy to 0.82 sigma.

Abstract

The present work begins by examining the early-Universe inflationary epoch of a special K-essence model, which incorporates a linear coupling term between the scalar field potential and the canonical Lagrangian. For the power law potential, we both numerically and analytically prove that the inflationary parameters such as the spectral index and tensor-to-scalar ratio are compatible with the recent BICEP/Keck observations. Continuing this work, our analysis based on comparing early-Universe observations with late-Universe measurements indicates that the tension on the Hubble parameter $H_0$ and the growth of structure parameter $S_8$ can be alleviated simultaneously. More precisely, compared to the standard $\Lambda$CDM model, our model can reduce $H_0$ tension to roughly $2.2 \sigma$ and the $S_8$ discrepancy diminishes to $0.82\sigma$.