A New Test of Dynamical Dark Energy Models and Cosmic Tensions in Ho\v{r}ava Gravity

TL;DR

This paper tests a Horava gravity-based dark energy model against cosmological data, finding partial support for non-flat universes and slight shifts in Hubble constant estimates, but also highlighting some limitations and areas for improvement.

Contribution

It provides the first comprehensive CMB, BAO, and SNe Ia data analysis of the Horava gravity dark energy model, including perturbations and non-flat geometries.

Findings

Preference for non-flat universes in data fits

Shift of H0 towards higher values, reducing tension

Results close to cosmic concordance, unlike non-flat LCDM

Abstract

Horava gravity has been proposed as a renormalizable, higher-derivative, Lorentz-violating quantum gravity model without ghost problems. A Horava gravity based dark energy (HDE) model for dynamical dark energy has been also proposed earlier by identifying all the extra (gravitational) contributions from the Lorentz-violating terms as an effective energy-momentum tensor in Einstein equation. We consider a complete CMB, BAO, and SNe Ia data test of the HDE model by considering general perturbations over the background perfect HDE fluid. Except from BAO, we obtain the preference of non-flat universes for all other data-set combinations. We obtain a positive result on the cosmic tensions between the Hubble constant H0 and the cosmic shear S8, because we have a shift of H0 towards a higher value, though not enough for resolving the H0 tension, but the value of S8 is unaltered. This is in contrast to a rather decreasing H0 but increasing S8 in a non-flat LCDM. For all other parameters, like Omega_m and Omega_Lambda, we obtain quite comparable results with those of LCDM for all data sets, especially with BAO, so that our results are close to a cosmic concordance between the datasets, contrary to the standard non-flat LCDM. We also obtain some undesirable features, like an almost null result on Omegak, which gives back the flat LCDM, if we do not predetermine the sign of Omegak, but we propose several promising ways for improvements by generalizing our analysis.