Scale hierarchy in Horava-Lifshitz gravity: a strong constraint from synchrotron radiation in the Crab nebula

TL;DR

This paper uses synchrotron radiation data from the Crab nebula to place strong constraints on the energy scale of higher order operators in Horava-Lifshitz gravity, indicating it must be much lower than the Lorentz breaking scale.

Contribution

It demonstrates that synchrotron radiation constraints effectively exclude the possibility of the Horava-Lifshitz scale being comparable to the Lorentz breaking scale in the matter sector.

Findings

Synchrotron radiation constrains the Horava-Lifshitz scale to be much lower than the Lorentz breaking scale.

Higher order operators in Horava-Lifshitz gravity are strongly constrained by astrophysical observations.

A mechanism is needed to suppress Lorentz violation percolation in the matter sector.

Abstract

Horava-Lifshitz gravity models contain higher order operators suppressed by a characteristic scale, which is required to be parametrically smaller than the Planck scale. We show that recomputed synchrotron radiation constraints from the Crab nebula suffice to exclude the possibility that this scale is of the same order of magnitude as the Lorentz breaking scale in the matter sector. This highlights the need for a mechanism that suppresses the percolation of Lorentz violation in the matter sector and is effective for higher order operators as well.