scholarly journals General relativistic nonideal fluid equations for dark matter from a truncated cumulant expansion

2020 ◽  
Vol 102 (6) ◽  
Author(s):  
Alaric Erschfeld ◽  
Stefan Floerchinger ◽  
Maximilian Rupprecht
Keyword(s):  
Dark Matter ◽  
Cumulant Expansion ◽  
Fluid Equations ◽  
General Relativistic

scholarly journals DARK MATTER, AND ITS DARKNESS

2006 ◽  
Vol 15 (12) ◽  
pp. 2267-2278 ◽  
Author(s):  
D. V. AHLUWALIA-KHALILOVA
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Cosmological Constant ◽  
Model Material ◽  
Representation Space ◽  
Spatial Curvature ◽  
The Standard Model ◽  
General Relativistic ◽  
Relativistic Description ◽  
Friedmann Robertson Walker

Assuming the validity of the general relativistic description of gravitation on astrophysical and cosmological length scales, we analytically infer that the Friedmann–Robertson–Walker cosmology with Einsteinian cosmological constant, and a vanishing spatial curvature constant, unambiguously requires a significant amount of dark matter. This requirement is consistent with other indications for dark matter. The same space–time symmetries that underlie the freely falling frames of Einsteinian gravity also provide symmetries which, for the spin one half representation space, furnish a novel construct that carries extremely limited interactions with respect to the terrestrial detectors made of the standard model material. Both the "luminous" and "dark" matter turn out to be residents of the same representation space but they derive their respective "luminosity" and "darkness" from either belonging to the sector with (CPT)2 = +𝟙, or to the sector with (CPT)2 = -𝟙.

scholarly journals Observational Role of Dark Matter in f(R) Models for Structure Formation

2018 ◽  
Vol 46 ◽  
pp. 1860045
Author(s):  
Murli Manohar Verma ◽  
Bal Krishna Yadav
Keyword(s):  
Dynamical System ◽  
Dark Matter ◽  
Fixed Points ◽  
Gravity Models ◽  
Stability Conditions ◽  
Cosmological Observations ◽  
General Relativistic ◽  
The Stability ◽  
The Universe

The fixed points for the dynamical system in the phase space have been calculated with dark matter in the [Formula: see text] gravity models. The stability conditions of these fixed points are obtained in the ongoing accelerated phase of the universe, and the values of the Hubble parameter and Ricci scalar are obtained for various evolutionary stages of the universe. We present a range of some modifications of general relativistic action consistent with the [Formula: see text]CDM model. We elaborate upon the fact that the upcoming cosmological observations would further constrain the bounds on the possible forms of [Formula: see text] with greater precision that could in turn constrain the search for dark matter in colliders.

scholarly journals RELATIVISTIC GALAXY ROTATIONS VERSUS DARK MATTER

2020 ◽  
Author(s):  
Angelo Loinger ◽  
Tiziana Marsico
Keyword(s):  
Dark Matter ◽  
Gravitational Effects ◽  
The Galaxy ◽  
General Relativistic ◽  
Relativistic Treatment

The gravitational effects ascribed to theDarkMatter can be explained with a general-relativistic treatment of the galaxy rotations.

scholarly journals GENERAL RELATIVISTIC VELOCITY: THE ALTERNATIVE TO DARK MATTER

2008 ◽  
Vol 23 (21) ◽  
pp. 1745-1755 ◽  
Author(s):  
F. I. COOPERSTOCK ◽  
S. TIEU
Keyword(s):  
Dark Matter ◽  
Newtonian Gravity ◽  
Relativistic Velocity ◽  
Concentrated Mass ◽  
Cluster Of Galaxies ◽  
Spherical Collapse ◽  
Test Particles ◽  
Open Case ◽  
General Relativistic ◽  
Weak Gravity

We consider the gravitational collapse of a spherically symmetric ball of dust in the general relativistic weak gravity regime. The velocity of the matter as viewed by external observers is compared to the velocity gauged by local observers. While the comparison in the case of very strong gravity is seen to follow the pattern familiar to the studies of test particles falling towards a concentrated mass, the case of weak gravity is very different. The velocity of the dust that is witnessed by external observers is derived for the critically open case and is seen to differ markedly from the expectations based upon Newtonian gravity theory. Viewed as an idealized model for a cluster of galaxies, we find that with the general relativistic velocity expression, the higher-than-expected constituent velocities observed can be readily correlated with the solely baryonic measure of the mass, obviating the need to introduce extraneous dark matter. It would be particularly valuable if a laboratory or space-based realization of a spherical collapse could be implemented to compare the velocity expression as a new test of general relativity.

The curvature effect on the gravitational collapse of interacting and non-interacting combination of dark matter and dark energy

2020 ◽  
Vol 35 (17) ◽  
pp. 2050078
Author(s):  
S. Z. Abbas ◽  
H. H. Shah ◽  
W. Chammam ◽  
H. Sun ◽  
Wasim Ul Haq ◽  
...  
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Gravitational Collapse ◽  
Space Time ◽  
Relativistic Astrophysics ◽  
Spherically Symmetric ◽  
Curvature Effect ◽  
De Formula ◽  
General Relativistic

The study of gravitational collapse is a very interesting phenomena in general relativistic astrophysics. Here, in this study we investigated the gravitational collapse of a spherically symmetric core of a star, constituted of dark matter (DM) ([Formula: see text]), in dark energy (DE) ([Formula: see text]) background. It was investigated that gravitational collapse of interacting and noninteracting combination of DM and DE yields BH formation. In this work, our main aim is to examine the effect of space–time curvature [Formula: see text] on the gravitational collapse of interacting and noninteracting combination of dark matter and DE. We achieve the visible influence of curvature on gravitational collapse analytically and interpret the results graphically.

scholarly journals DARK ENERGY, DARK MATTER AND GRAVITY

2007 ◽  
Vol 16 (12a) ◽  
pp. 2003-2012 ◽  
Author(s):  
ORFEU BERTOLAMI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Solar System ◽  
Physical Theory ◽  
Scalar Fields ◽  
High Accuracy ◽  
Scalar Theory ◽  
General Relativistic ◽  
Cosmological Tests ◽  
Theory Of Gravity

We discuss the motivation for high accuracy relativistic gravitational experiments in the solar system and complementary cosmological tests. We focus our attention on the issue of distinguishing a generic scalar theory of gravity as the underlying physical theory from the usual general-relativistic picture, where one expects the presence of fundamental scalar fields associated, for instance, with inflation, dark matter and dark energy.

Terrestrial Sagnac delay in scalar–tensor–vector–gravity

2021 ◽  
pp. 2150042
Author(s):  
R. Kh. Karimov ◽  
R. N. Izmailov ◽  
K. K. Nandi
Keyword(s):  
Dark Matter ◽  
Neutron Star ◽  
Modified Gravity ◽  
Dimensionless Parameter ◽  
Potential Candidate ◽  
Central Source ◽  
Cosmological Data ◽  
General Relativistic ◽  
Range Of Values ◽  
Galaxy Rotation Curves

The scalar–tensor–vector–gravity (STVG), a prototype of modified gravity developed by Moffat, can correctly explain galaxy rotation curves, cluster dynamics, Bullet Cluster phenomena and cosmological data without invoking the observationally elusive general relativistic (GR) dark matter. Further, recent observations of neutron star masses are shown to defy some GR predictions, whereas STVG turns out to be more consistent with those observations. These successes indicate that STVG could be a potential candidate for a new theory of gravity. However, an important question concerns the possible range of values of the STVG dimensionless parameter [Formula: see text] imposed by various physical scenarios. In the literature, the range [Formula: see text] corresponding to different central source masses has been suggested. We show here that the [Formula: see text] can be considerably constrained into the range [Formula: see text] assuming that the updated GPS fluctuation does not exceed the [Formula: see text]-dependent correction to the terrestrial Sagnac delay.

QUANTUM CONDENSATES IN EXTREME GRAVITY: IMPLICATIONS FOR COLD STARS AND DARK MATTER

2008 ◽  
Vol 17 (03n04) ◽  
pp. 603-609
Author(s):  
M. P. SILVERMAN
Keyword(s):  
Dark Matter ◽  
Scattering Length ◽  
Hydrostatic Equilibrium ◽  
Dark Matter Halos ◽  
Mass Limit ◽  
Composite Bosons ◽  
Galactic Dark Matter ◽  
General Relativistic ◽  
Gravitating Systems ◽  
Relativistic Condition

Stable end-point stars currently fall into two distinct classes — white dwarfs and neutron stars — differing enormously in central density and radial size. No stable cold dead stars are thought to span the intervening densities or have masses beyond ~2–3 solar masses. I show, however, that the general-relativistic condition of hydrostatic equilibrium augmented by the equation of state of a neutron condensate at 0 K generates stable sequences of cold stars that span the density gap and can have masses well beyond prevailing limits. The radial sizes and mass limit of each sequence are determined by the mass and scattering length of the composite bosons. Solutions for hypothetical bosons of ultrasmall mass and large scattering length yield huge self-gravitating systems of low density, resembling galactic dark matter halos.

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