Mirror Matter, Mirror Gravity and Galactic Rotational Curves

TL;DR

This paper explores a modified gravity model with separate matter components and mixing gravitational fields, explaining galactic rotation curves and addressing dark matter distribution issues.

Contribution

It introduces a model with two gravitational eigenstates that can explain flat galactic rotation curves without extended dark matter halos.

Findings

Reproduces observed rotational curves for various galaxy sizes.

Suggests a Yukawa radius around 10 kpc for galaxy-scale effects.

Offers a potential solution to the cusp problem in dark matter halos.

Abstract

We discuss astrophysical implications of the modified gravity model in which the two matter components, ordinary and dark, couple to separate gravitational fields that mix to each other through small mass terms. There are two spin-2 eigenstates: the massless graviton that induces universal Newtonian attraction, and the massive one that gives rise to the Yukawa-like potential which is repulsive between the ordinary and dark bodies. As a result the distances much smaller than the Yukawa radius $r_m$ the gravitation strength between the two types of matter becomes vanishing. If $r_m \sim 10$ kpc, a typical size of a galaxy, there are interesting implications for the nature of dark matter. In particular, one can avoid the problem of the cusp that is typical for the cold dark matter halos. Interestingly, the flat shape of the rotational curves can be explained even in the case of the collisional and dissipative dark matter (as e.g. mirror matter) that cannot give the extended halos but instead must form galactic discs similarly to the visible matter. The observed rotational curves for the large, medium-size and dwarf galaxies can be nicely reproduced. We also briefly discuss possible implications for the direct search of dark matter.