Overall observational constraints on the running parameter \lambda of Horava-Lifshitz gravity

TL;DR

This paper uses cosmological observational data to tightly constrain the running parameter  of Horava-Lifshitz gravity, finding it very close to 1, but does not address theoretical issues of the model.

Contribution

It provides the first comprehensive observational constraints on the  parameter of Horava-Lifshitz gravity using multiple cosmological data sets.

Findings

 is constrained to |-1|\u2264 0.02 at 1.

Best fit value of  is approximately 1.002.

Observational data does not resolve theoretical issues of the model.

Abstract

We use observational data from Type Ia Supernovae (SNIa), Baryon Acoustic Oscillations (BAO), and Cosmic Microwave Background (CMB), along with requirements of Big Bang Nucleosynthesis (BBN), to constrain the running parameter $\lambda$ of Horava-Lifshitz gravity, which determines the flow between the Ultra-Violet and the Infra-Red. We consider both the detailed and non-detailed balance versions of the gravitational sector, and we include the matter and radiation sectors. Allowing for variation of all the parameters of the theory, we construct the likelihood contours and we conclude that in $1\sigma$ confidence $\lambda$ is restricted to $|\lambda-1|\lesssim0.02$, while its best fit value is $|\lambda_{b.f}-1|\approx0.002$. Although this observational analysis restricts the running parameter $\lambda$ very close to its IR value 1, it does not enlighten the discussion about the theory's possible conceptual and theoretical problems.