An alternative to dark matter: do braneworld effects hold the key?

Abstract

An alternative way of explaining astrophysical observations without dark matter is proposed. In the braneworld scenario, where our universe is visualised as a 4-dimensional hypersurface embedded in a higher dimensional spacetime, the effective Einstein equation on the brane contains extra terms. We show that the astrophysical observations which are usually explained by particle dark matter, can be explained in this modified theory of gravity via those extra terms, without the need for dark matter. As specific example, we model X-ray profiles of clusters of galaxies and the galaxy rotation curves which are consistent with observations. Further, we investigate whether gravitational lensing can discriminate between the two possibilities. Significant differences between the values of the deflection angles are obtained, which can be tested in future observations.