On the energy flow of $\lambda$ in Ho\v{r}ava-Lifshitz cosmology

TL;DR

This paper analyzes the cosmological implications of Hořava-Lifshitz gravity, especially the running of the parameter λ, using diverse observational data to constrain its deviation from general relativity.

Contribution

It provides new observational bounds on λ in two formulations of Hořava-Lifshitz gravity, highlighting how data choices influence these constraints.

Findings

Bound on λ in detailed balance scenario: 1.02726±0.00012

Bound on λ beyond detailed balance: 0.9949+0.0045−0.0046

Removing low-redshift data shifts λ closer to UV values and widens errors

Abstract

Ho\v{r}ava-Lifshitz gravity has been proposed as a ghost-free quantum gravity model candidate with an anisotropic UV-scaling between space and time. We present here a cosmological background analysis of two different formulations of the theory, with particular focus on the running of the parameter $\lambda$. Using a large dataset consisting of Cosmic Microwave Background data from {\it Planck}, Pantheon+ supernovae catalogue, SH0ES Cepheid variable stars, Baryon acoustic oscillations (BAO), Cosmic Chronometers, and gamma-ray bursts (GRB), we arrive at new bounds on the cosmological parameters, in particular $\lambda$, which describes deviation from classical general relativity. For the detailed balance scenario we arrive at the bound $\lambda=1.02726\pm0.00012$, and for beyond detailed balance the limit reads $\lambda=0.9949^{+0.0045}_{-0.0046}$. We also study the influence of different data sets and priors, and we find that removing low-redshift data generally moves $\lambda$ closer towards UV values, whilst simultaneously widening the error bars. In the detailed balance scenario, this effect is more noticeable, and $\lambda$ takes on values that are significantly below unity, which corresponds to the infrared limit of the theory.