Testing Ho\v{r}ava-Lifshitz gravity using thin accretion disk properties

TL;DR

This paper explores how properties of accretion disks around black holes can be used to observationally test the predictions of Horava-Lifshitz gravity, comparing them with standard general relativity results.

Contribution

It introduces a method to test Horava gravity through accretion disk emissions, providing potential observational signatures to distinguish it from Einstein gravity.

Findings

Accretion disk spectra show distinctive features in Horava gravity.

Energy flux and temperature profiles differ from general relativity.

Potential for astrophysical observations to constrain Horava gravity models.

Abstract

Recently, a renormalizable gravity theory with higher spatial derivatives in four dimensions was proposed by Horava. The theory reduces to Einstein gravity with a non-vanishing cosmological constant in IR, but it has improved UV behaviors. The spherically symmetric black hole solutions for an arbitrary cosmological constant, which represent the generalization of the standard Schwarzschild-(A)dS solution, has also been obtained for the Horava-Lifshitz theory. The exact asymptotically flat Schwarzschild type solution of the gravitational field equations in Horava gravity contains a quadratic increasing term, as well as the square root of a fourth order polynomial in the radial coordinate, and it depends on one arbitrary integration constant. The IR modified Horava gravity seems to be consistent with the current observational data, but in order to test its viability more observational constraints are necessary. In the present paper we consider the possibility of observationally testing Horava gravity by using the accretion disk properties around black holes. The energy flux, temperature distribution, the emission spectrum as well as the energy conversion efficiency are obtained, and compared to the standard general relativistic case. Particular signatures can appear in the electromagnetic spectrum, thus leading to the possibility of directly testing Horava gravity models by using astrophysical observations of the emission spectra from accretion disks.