Modified Newtonian dynamics (MOND) is an alternative theory of gravity that aims to explain large-scale dynamics without recourse to any form of dark matter. However the theory is incomplete, lacking a relativistic counterpart, and so makes no definite predictions about gravitational lensing. The most obvious form that MONDian lensing might take is that photons experience twice the deflection o...

X-ray emitting clusters of galaxies are considered in the context of modified Newtonian dynamics (MOND). I show that self-gravitating isothermal gas spheres are not good representations of rich clusters with respect to the radial gas density distribution as indicated by the X-ray surface brightness. Pure gas spheres with a density distribution described by a β model, as observed, also fail beca...

We discuss a comparison of models for the formation of disk galaxies both in a Universe dominated by cold dark matter (CDM) and one in which the force law is given by modified Newtonian dynamics (MOND). Our main aim is to address the claim made by McGaugh & de Blok that CDM suffers from severe fine-tuning problems, which are circumvented under MOND. As we show, CDM indeed requires some amount o...

MOND, invented by Milgrom, is a phenomenological scheme whose basic premise is that the visible matter distribution in a galaxy or cluster of galaxies alone determines its dynamics. MOND fits many observations surprisingly well. Could it be that there is no dark matter in these systems and we witness rather a violation of Newton’s universal gravity law ? If so, Einstein’s general relativity wou...

We investigate the mass profiles of clusters in MOND for a sample of galaxy groups and clusters with temperatures ranging from 0.7 to 8.9 keV. We confirm that a huge hidden mass component, about 1.5 to 4 times more massive than the total visible mass (at the last measured radii, dropping thereafter), is needed to account for the hydrostatic equilibrium of these clusters. For the massive systems...

The dynamics of the Magellanic Stream (MS) as a series of clouds extending from the Magellanic Clouds (MCs) to the south Galactic pole is affected by the distribution and the amount of matter in the Milky Way. We calculate the gravitational effect of the Galactic disk on the MS in the framework of modified Newtonian dynamics(MOND) and compare with observations of the Stream’s radial velocity. W...

Dark Matter (DM) theories and mass-tracing-light theories like MOND are by construction nearly degenerate on galactic scales, but not when it comes to the predicted shapes of Roche Lobes of a two-body system (e.g., a globular cluster orbiting a host galaxy). We show that the flattening of the Roche lobe is sensitive to the function μ(g) in modification of the law of gravity. We generalise the a...

Since Bekenstein’s (2004) creation of his Tensor-Vector-Scalar theory (TeVe S), the Modified Newtonian dynamics (MOND) paradigm has been redeemed from the embarrassment of lacking a relativistic version. One primary success of TeVe S is that it provides an enhancement of gravitational lensing, which could not be achieved by other MONDian theories. Following Bekenstein’s work, we investigate the...