It is well known, but under-appreciated in astrophysical applications, that it is possible for gravity to take on a life of its own in the form of Weyl-curvature-only metrics (note that we are referring to the Weyl-only solutions of ordinary General...
This paper aims to explore whether astrophysical observations, primarily galaxy rotation curves, result from covarying coupling constants (CCC) rather than from dark matter. We have shown in earlier papers that cosmological observations, such as supe...
We examine some of the consequences of the Exochronous (timeless) metric and the associated ΣGR cosmological model for the formation of galaxies, and, in particular, their characteristic rotation curves. We show how the cumulative curvature fro...
Using the multiplicity of solutions for the projectable case of the covariant extension of Hořava-Lifshitz gravity, we show that an appropriate choice for the auxiliary field allows for an effective description of galaxy rotation curves. This descrip...
Using the classical vacuum solutions of Newtonian gravity that do not explicitly involve matter, dark matter, or the gravitational constant, subject to an averaging process, a form of gravity relevant to the flattening of galaxy rotation curves resul...
A new simple expression for the circular velocity of spiral galaxies is proposed and tested against HI Nearby Galaxy Survey (THINGS) data set. Its accuracy is compared with the one coming from MOND.
Eicheon properties are discussed. It is shown that the eicheon surface allows setting a boundary condition for the vacuum polarization and obtaining a solution describing the dark matter tail in the Milky Way Galaxy. That is, the dark matter in the M...
We suggest a new explanation of the flatness of galaxies rotation curves without invoking dark matter. For this purpose, a new gravitational tensor field is introduced in addition to the metric tensor.
The flattening of spiral-galaxy rotation curves is unnatural in view of the expectations from Kepler’s third law and a central mass. It is interesting, however, that the radius-independence velocity is what one expects in one less dimension. In our t...
An accurate computational method is presented for determining the mass distribution in a mature spiral galaxy from a given rotation curve by applying Newtonian dynamics for an axisymmetrically rotating thin disk of finite size with or without a centr...
The aim of this paper is to test the need for non-baryonic dark matter in the context of galactic rotation and the apparent difference between distributions of galactic mass and luminosity. We present a set of rotation curves and 3.6 μm surface br...
Spiral galaxies are spinning, internally densified objects. The Virial Theorem explains galactic rotation curves via its linkage of the rotation rate to the gravitational self-potential (Ug) and the moment of inertia of oblate spheroids. We devise a...
The most cited evidence for (non-baryonic) dark matter has been an apparent lack of visible mass to gravitationally support the observed orbital velocity of matter in rotating disk galaxies, yet measurement of the mass of celestial objects cannot be...
In this paper, we show how baryonic physics can solve the problem of the striking diversity in dwarf galaxy rotation curves shapes. To this aim, we compare the distribution of galaxies of the SPARC sample, in the plane V2kpc-VRlast (V2kpc being the g...
The rotational velocity curve, which is the circular velocity profile of the stars and gas in a spiral galaxy as a function of their distance from the galactic center, plays an important role in the kinematic and dynamic investigation of spiral galax...
Proposed explanations of galactic rotation curves (RC = tangential velocity vs. equatorial radius, determined from Doppler measurements) involve dramatically different assumptions. A dominant, original camp invoked huge amounts of unknown, non-baryon...
In the Newtonian limit of general relativity a force acting on a test mass in a central gravitational field is conventionally defined by the attractive Newtonian gravity (inverse square) term plus a small repulsive cosmological force, which is propor...
In this paper, we further elaborate on the Bose–Einstein condensate (BEC) dark matter model extended in our previous work [Phys. Rev. D 2020, 102, 083510] by the inclusion of sixth-order (or three-particle) repulsive self-interaction term. Herei...
Motivated by the SU(2)CMB modification of the cosmological model ΛCDM, we consider isolated fuzzy-dark-matter lumps, made of ultralight axion particles whose masses arise due to distinct SU(2) Yang–Mills scales and the Planck mass MP. In contrast to...
Galaxy rotation curve (RC) fitting is an important technique which allows the placement of constraints on different kinds of dark matter (DM) halo models. In the case of non-phenomenological DM profiles with no analytic expressions, the art of findin...
Spiral galaxies and their rotation curves have key characteristics of differentially spinning objects. Oblate spheroid shapes are a consequence of spin and reasonably describe galaxies, indicating that their matter is distributed in gravitationally i...
We review the current status of the study of rotation curve (RC) of the Milky Way, and present a unified RC from the Galactic Center to the galacto-centric distance of about 100 kpc. The RC is used to directly calculate the distribution of the surfac...
Recent independent observations using several different telescope systems and analysis methods have provided evidence of parity violation between the numbers of galaxies that spin in opposite directions. On the other hand, other studies argue that no...
Despite over a century of research, the physics of galaxy rotation is not yet fully understood, and there is a clear discrepancy between the observed mass of galaxies and their rotational velocity. Here, we report on another observation of tension be...
The cold dark-matter model successfully explains both the emergence and evolution of cosmic structures on large scales and, when we include a cosmological constant, the properties of the homogeneous and isotropic Universe. However, the cold dark-matt...
Dark matter in the Milky Way is explained by the F-type of vacuum polarization, which could represent dark radiation. A nonsingular solution for dark radiation exists in the presence of eicheon (i.e., black hole in old terminology) in the galaxy&rsqu...
It is already known that a simple nonlocal de Sitter gravity model, which we denote as dS gravity, contains an exact vacuum cosmological solution that mimics dark energy and dark matter and is in very good agreement with the standard model of cosmolo...
In a recent paper, we have a shown that the flattening of galactic rotation curves can be explained by retardation. However, this will rely on a temporal change of galactic mass. In our previous work, we kept only second order terms of the retardatio...
This Special Issue was motivated by the disparate explanations of galactic dynamics promulgated by different philosophical camps [...]
In a recent paper, we have a shown that the flattening of galactic rotation curves can be explained by retardation. However, this relies on a temporal change of galactic mass. In our previous work, we kept only second order terms of the retardation t...
A recent study using weak gravitational lensing revealed that the rotation curves of some isolated galaxies are found at a very large distance from their galactic centres. This may provide strong evidence supporting Modified Newtonian Dynamics (MOND)...
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 words, fi...
Noncommutative-like model (NC-like) is an interesting alternative inspired by string theory to understand and describe the velocity rotation curves of galaxies without the inclusion of dark matter particles. In a natural way, a Gaussian density profi...
As an alternative gravitational theory to General Relativity (GR), Conformal Gravity (CG) can be verified through astronomical observations. Currently, Mannheim and Kazanas have provided vacuum solutions for cosmological and local gravitational syste...
Gravity and electromagnetic interactions are the only fundamental physical interactions (outside the nuclear domain). In this work, we shall concentrate on Hamiltonians containing gravitational interaction, which according to general relativity must...
We confront a non-relativistic Bose–Einstein Condensate (BEC) model of light bosons interacting gravitationally either through a Newtonian or a Yukawa potential with the observed rotational curves of 12 dwarf galaxies. The baryonic component is...
Dark matter (DM) is one of the biggest mystery in the Universe. In this review, we start reporting the evidences for this elusive component and discussing about the proposed particle candidates and scenarios for such phenomenon. Then, we focus on rec...
We propose a simple geometrical mechanism for the flattening of galactic rotation curves at large distances, the local compression of field lines around their planes induced either by the presence of thin string-like objects at the centers of galaxie...
We demonstrate that the existence of a Noether symmetry in f ( R ) theories of gravity gives rise to an additional gravitational radius, besides the standard Schwarzschild one, determining the dynamics at galactic scales. By this feature, it...
[-5]The applications of Newtonian dynamics in galactic scales have shown that the inverse square law is incompatible with the amount of visible mass in the form of stars and molecular clouds. This manifests as the rotational curves of galaxies being...
Disk galaxies have a typical dimension of a few tens of kiloparsecs. It follows from the theory of general relativity that any signal originating from the galactic center will be noticed at the outskirts of the galaxy only tens of thousands of years...
In our previous study, (Eur Phys J Plus 135:362, 2020 & Eur Phys J Plus 135:637, 2020), we have discussed the possible existence of the dark-matter-admixed pulsars, located in dwarf as well as in massive spiral galaxies (based on Singular Isother...
We show that Einstein’s conformal gravity can explain, simply, and on the geometric ground, galactic rotation curves, without the need to introduce any modification in both the gravitational as well as in the matter sector of the theory. The ge...
We resume our analysis of Newtonian Fractional-Dimension Gravity (NFDG), an alternative gravitational model that does not require the dark matter (DM) paradigm. We add three more galaxies (NGC 6946, NGC 3198, NGC 2841) to the catalog of those studied...
Recently, we put forward a framework where the dark matter (DM) component within virialized halos is subject to a non-local interaction originated by fractional gravity (FG) effects. In previous works, we demonstrated that such a framework can substa...
We apply Newtonian fractional-dimension gravity (NFDG), an alternative gravitational model, to some notable cases of galaxies with little or no dark matter. In the case of the ultra-diffuse galaxy AGC 114905, we show that NFDG methods can effectively...
A static structure of matter, extremely compressed to the state of a Bose–Einstein condensate by its own gravitational field, is considered. Instead of the widely spread restriction detgik<0, I used a weaker condition of regularity: all inva...
We derive an effective gravitational potential, induced by the quantum wavefunction of a physical vacuum of a self-gravitating configuration, while the vacuum itself is viewed as the superfluid described by the logarithmic quantum wave equation. We d...
Monitoring of the lens system JVAS B0218+357 with the Fermi Gamma-ray Space Telescope measured a different time delay to that derived from radio observations. We have re-analysed three months of archival Very Large Array data to produce variability c...
The baryonic mass–velocity relation provides an important test of different galaxy dynamics models such as Lambda–cold dark matter (ΛCDM) and alternatives like Modified Newtonian Dynamics (MOND). Novel nonlinear density wave theory...
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