The Milky Way rotation curve in Horava - Lifshitz theory

TL;DR

This paper investigates how Horava-Lifshitz theory modifies gravitational potential and rotation curves, specifically analyzing the Milky Way, and concludes that dark matter remains necessary despite the modifications.

Contribution

It derives a modified gravitational potential in HL theory and applies it to the Milky Way, showing the theory's limitations in replacing dark matter.

Findings

HL theory introduces additional potential terms affecting rotation curves

Fitting Milky Way data with HL potential still requires dark matter

Dark matter profile estimates need revision under HL modifications

Abstract

The Horava - Lifshitz (HL) theory has recently attracted a lot of interest as a viable solution to some quantum gravity related problems and the presence of an effective cosmological constant able to drive the cosmic speed up. We show here that, in the weak field limit, the HL proposal leads to a modification of the gravitational potential because of two additive terms (scaling respectively as $r^2$ and $r^{-4}$) to the Newtonian $1/r$ potential. We then derive a general expression to compute the rotation curve of an extended system under the assumption that the mass density only depends on the cylindrical coordinates $(R, z)$ showing that the HL modification induces a dependence of the circular velocity on the mass function which is a new feature of the theory. As a first exploratory analysis, we then try fitting the Milky Way rotation curve using its visible components only in order to see whether the HL modified potential can be an alternative to the dark matter framework. This turns out not to be the case so that we argue that dark matter is still needed, but the amount of dark matter and the dark halo density profile have to be revised according to the new HL potential.