Related papers: Galaxy rotation curves. The theory
Conformal geometry is considered within a general relativistic framework. An invariant distant for proper time is defined and a parallel displacement is applied in the distorted space-time, modifying Einstein's equation appropriately. A…
We continue to study the spherically symmetric vacuum solutions of the tensor-four-scalars theory which is a modification of general relativity. Our aim is to construct vacuum solutions with asymptotically constant circular velocity curves…
Modern astrophysical and cosmological models are faced with two severe theoretical difficulties, that can be summarized as the dark energy and the dark matter problems. Relative to the former, it has been stated that cosmology has entered a…
It has long been known that Newtonian dynamics applied to the visible matter in galaxies and clusters does not correctly describe the dynamics of those systems. While this is generally taken as evidence for dark matter it is in principle…
It has been suggested that the observed flat rotation curves of disk galaxies can be a peculiar effect of General Relativity (GR) rather than evidence for the presence of dark matter (DM) halos in Newtonian gravity. In Ciotti (2022) the…
The rotation curves of low surface brightness galaxies provide a unique data set with which to test alternative theories of gravitation over a large dynamic range in size, mass, surface density, and acceleration. Many clearly fail,…
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…
A solution for the problem of understanding observed rotation curves in galaxies without the introduction of dark matter halos is presented. This solution has been obtained upon considering the distribution of masses in the expanding…
While galaxy rotation curves provide one of the most powerful methods for measuring dark matter profiles in the inner regions of rotation-supported galaxies, at the dwarf scale there are factors that can complicate this analysis. Given the…
A unified parametrization of the circular velocity, which accurately fits 850 galaxy rotation curves without needing in advance the knowledge of the luminous matter components, nor a fixed dark matter halo model, is proposed. A notable…
The gravitational field outside of astrophysical black holes is completely described by their mass and spin frequency, as expressed by the no-hair theorems. These theorems assume vacuum spacetimes, and thus they apply only to black holes…
General relativistic deflection of light by mass, dipole, and quadrupole moments of gravitational field of a moving massive planet in the Solar system is derived in the approximation of the linearized Einstein equations. All terms of order…
The effects of several dark energy models on gravitational time delay of particles with non-zero mass are investigated and analytical expressions for the same are obtained at the first order accuracy. Also the expression for gravitational…
We study a noncommutative deformation of general relativity where the gravitational field is described by a matrix-valued symmetric two-tensor field. The equations of motion are derived in the framework of this new theory by varying a…
We develop a cosmological model based on action-dependent Lagrangian theories. The main feature here is the nonconservation of the energy momentum tensor due to the nontrivial geometrical construction of the theory. We provide the basic set…
It is a well-known fact that the gravitational effect of dark matter in galaxies is only noticeable when the orbital accelerations drop below $a_0 \simeq 2\times 10^{-8}$ cm s$^{-1}$ (Milgrom's Law). This peculiarity of the dynamic…
We propose a Machian model of gravitational interaction at galactic scales to explain the rotation curves of these large structures without the need for dark matter or MOND.
The non-Keplerian galactic rotational curves and the gravitational lensing data strongly indicate a significant dark matter component in the universe. Moreover, these data can be combined to deduce the equation of state of dark matter. Yet,…
We consider a toy model for the supermassive compact object at the galactic center that does not require the presence of a black hole. We assume a matter distribution of weakly interacting particles with a density profile inferred from dark…
In this paper we study a stellar dynamic model for the stars' rotational-dynamics, with a distribution of its own mass, rotating around its center with a higher density, like spiral galaxies happen, by means of a classical calculus of the…