Related papers: Testing universal dark-matter caustic rings with g…
The missing gravity in galaxies requires dark matter, or alternatively a modification of gravity or inertia. These theoretical possibilities of fundamental importance may be distinguished by the statistical relation between the observed…
Cold Dark Matter (CDM) has become the standard modern theory of cosmological structure formation. Its predictions appear to be in good agreement with data on large scales, and it naturally accounts for many properties of galaxies. But…
We investigate the possibility to explain theoretically the galaxy rotation curves by a gravitational potential in total absence of dark matter. To this aim an analytic fourth-order theory of gravity, nonminimally coupled with a massive…
Clusters of galaxies are studied from a theoretical point of view, comparing with observational results whenever possible. The problem is approached both analytically as well as by means of high-resoultion numerical simulations. The dark…
In this work the phenomenology of models possessing a non-minimal coupling between matter and geometry is discussed, with a particular focus on the possibility of describing the flattening of the galactic rotation curves as a dynamically…
We compare proposed solutions to the core vs cusp issue of spiral galaxies, which has also been framed as a diversity problem, and demonstrate that the cuspiness of dark matter halos is correlated with the stellar surface brightness. We…
In this review we consider various ring structures that are observed in galaxies. Formation and evolution of the rings are interesting problems in studies of galactic morphology. They are related to such fundamental aspects of galactic…
When dealing with galactic dynamics, or more specifically, with galactic rotation curves, one basic assumption is always taken: the frame of reference relative to which the rotational velocities are given is assumed to be inertial. In other…
A galaxy is modeled as a stationary axially symmetric pressure-free fluid in general relativity. For the weak gravitational fields under consideration, the field equations and the equations of motion ultimately lead to one linear and one…
This paper gives an overview of the attempts to determine the distribution of dark matter in low surface brightness disk and gas-rich dwarf galaxies, both through observations and computer simulations. Observations seem to indicate an…
We discuss the possible dynamical role of extended cosmic defects on galactic scales, specifically focusing on the possibility that they may provide the dark matter suggested by the classical problem of galactic rotation curves. We…
Recent observations indicate that dark matter haloes have flat central density profiles. Cosmological simulations with non-baryonic dark matter predict however self similar haloes with central density cusps. This contradiction has lead to…
Collapsing collisionless particle systems form gravitational bound halos with cuspy density profiles. Also hierarchical merging of these systems produce remnants with cuspy central density profiles. These results lead to the assumption of…
Cold, dense clouds of gas have been proposed as baryonic candidates for the dark matter in Galactic haloes, and have also been invoked in the Galactic disc as an explanation for the excess faint sub-mm sources detected by SCUBA. Even if…
Taking the flat rotation curve as input and treating the matter content in the galactic halo region as perfect fluid, we obtain space time metric at the galactic halo region in the framework of general relativity. We find that the resultant…
Unhappily, there has been a maelstrom of problems for dark matter theories over the last few years and many serious difficulties still have no resolution in sight. This article reviews the evidence for dark matter in galaxies. The haloes…
The concept of dark matter in the Universe and its components has been discussed in the 1930s by several authors, and in particular by Oort (1932) and Zwicky (1933). However, it is only in the 1970s that the existence of dark matter was…
We derive a formula for the velocity distribution of an axially symmetric galaxy where the mass density is corrected using the mass formula from special relativity. We take some reasonable test mass densities and numerically compute the…
The observation of flat rotation curves in asymptotic region of galaxies implies that the dark matter density profile decreases exponentially with the gravitational potential in this region. It is curious that this behavior is identical to…
There should be two ways to describe the flat rotation curves of galaxies and cluster of galaxies. Either one can introduce a dark matter component for the matter filling the halo, or by modifying the gravity theory and give the flat…