Dark Halo or Bigravity?

TL;DR

This paper explores whether modifications in bigravity theories combined with mirror matter models can explain galactic rotation curves and the distribution of dark matter, suggesting a varying Newton constant at different scales.

Contribution

It proposes a bigravity framework with mirror matter to account for galactic rotation curves without ad-hoc dark matter profiles, introducing a scale-dependent Newton constant.

Findings

Bigravity models can reproduce observed galactic rotation curves.

The Newton constant varies significantly at different galactic scales.

Mirror matter provides a viable dark matter candidate within this framework.

Abstract

Observations show that about the 20% of the Universe is composed by invisible (dark) matter (DM), for which many candidates have been proposed. In particular, the anomalous behavior of rotational curves of galaxies (i.e. the flattening at large distance instead of the Keplerian fall) requires that this matter is distributed in an extended halo around the galaxy. In order to reproduce this matter density profiles in Newtonian gravity and in cold dark matter (CDM) paradigm (in which the DM particles are collisionless), many ad-hoc approximations are required. The flattening of rotational curves can be explained by a suitable modification of gravitational force in bigravity theories, together with mirror matter model that predicts the existence of a dark sector in which DM has the same physical properties of visible matter. As an additional result, the Newton constant is different at distances much less and much greater than 20 kpc.