scholarly journals Can a negative-mass cosmology explain dark matter and dark energy?

2019 ◽  
Vol 626 ◽  
pp. A5 ◽  
Author(s):  
H. Socas-Navarro
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Model ◽  
Large Scale ◽  
Dark Matter Halos ◽  
Challenging Problem ◽  
Speed Of Light ◽  
Negative Mass ◽  
Galactic Dark Matter

A recent study by Farnes (2018, A&A, 620, A92) proposed an alternative cosmological model in which both dark matter and dark energy are replaced with a single fluid of negative mass. This paper presents a critical review of that model. A number of problems and discrepancies with observations are identified. For instance, the predicted shape and density of galactic dark matter halos are incorrect. Also, halos would need to be less massive than the baryonic component, otherwise they would become gravitationally unstable. Perhaps the most challenging problem in this theory is the presence of a large-scale version of the “runaway effect”, which would result in all galaxies moving in random directions at nearly the speed of light. Other more general issues regarding negative mass in general relativity are discussed, such as the possibility of time-travel paradoxes.

Dark Matter

2018 ◽  
pp. 169-174
Author(s):  
Alvaro De Rújula
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Solar Eclipse ◽  
Gravitational Lensing ◽  
Virial Theorem ◽  
Dark Matter Halos ◽  
Gravitational Lenses ◽  
Coma Cluster ◽  
Cluster Of Galaxies ◽  
Galactic Dark Matter

What we know or do not know about dark matter. The evidence for its existence, first found by Fritz Zwicky. The “virial theorem” and the Coma cluster. The rotation curves of galaxies. Galactic dark-matter halos. Gravitational lensing and the May 1919 solar eclipse, a thiumph of General Relativity that propelled Einstein to his fame. The deflection of starlight by the eclipsed Sun. Gravitational lenses, Einstein rings, and Smilie. Gravitational-lensing and evidence for dark matter in the Bullet cluster of galaxies.

scholarly journals Warm dark matter and Hubble constant tensions

2019 ◽  
pp. 46-48 ◽  
Author(s):  
S. Parnovsky
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Energy Density ◽  
Cosmological Model ◽  
Hubble Constant ◽  
Baryonic Matter ◽  
Speed Of Light

The tensions between the values of Hubble constant obtained from the early and the late Universe could be eliminated if we use the ΛWDM cosmological model with dark energy, baryonic matter and warm dark matter (WDM) with characteristic velocities about 16 % of the speed of light. A pressure of WDM is equal to its energy density multiplied by factor 0.009.

scholarly journals Dark Energy and Cosmological Model

2020 ◽  
Vol 10 (2) ◽  
Author(s):  
Radhika Deshmukh
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Model ◽  
Empty Space ◽  
Space Time ◽  
Astronomical Observation ◽  
Quantum Level ◽  
Recent Modification ◽  
Time Expansion

Today the space of our universe is filled with invisible stuff matter which expanding under the action of gravity which was dark matter. In 1990’s astronomical observation and theoretical calculation was leading astrophysicists to believe that not only the dark matter but also there is vacuum empty space filled in universe that is dark energy. It is suggested that the apparently disparate cosmological phenomenon attributed to so called “dark matter” and dark energy arise from quantum level of space -time itself. This creation of space time results in metric expansion. A recent modification of Einstein’s theory of general relativity by Chadwick, Hodgkinson and McDonald incorporate space time expansion. Recent evidence predicts that apparent amount of dark matter increases with age of universe. In addition proposal leads to the same result for the small but non-vanishing cosmological constant, related to dark energy.

scholarly journals FORMATION OF DARK MATTER HALOES IN A HOMOGENEOUS DARK ENERGY UNIVERSE

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1397-1403
Author(s):  
L. MARASSI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Large Scale ◽  
State Parameter ◽  
Mass Function ◽  
Accelerated Expansion ◽  
X Ray ◽  
Energy Models ◽  
Dark Energy Component ◽  
Standard Press

Several independent cosmological tests have shown evidences that the energy density of the universe is dominated by a dark energy component, which causes the present accelerated expansion. The large scale structure formation can be used to probe dark energy models, and the mass function of dark matter haloes is one of the best statistical tools to perform this study. We present here a statistical analysis of mass functions of galaxies under a homogeneous dark energy model, proposed in the work of Percival (2005), using an observational flux-limited X-ray cluster survey, and CMB data from WMAP. We compare, in our analysis, the standard Press–Schechter (PS) approach (where a Gaussian distribution is used to describe the primordial density fluctuation field of the mass function), and the PL (power–law) mass function (where we apply a non-extensive q-statistical distribution to the primordial density field). We conclude that the PS mass function cannot explain at the same time the X-ray and the CMB data (even at 99% confidence level), and the PS best fit dark energy equation of state parameter is ω = -0.58, which is distant from the cosmological constant case. The PL mass function provides better fits to the HIFLUGCS X-ray galaxy data and the CMB data; we also note that the ω parameter is very sensible to modifications in the PL free parameter, q, suggesting that the PL mass function could be a powerful tool to constrain dark energy models.

scholarly journals The Dark Sector in the Baryon Phase Transition Cosmology

2019 ◽  
Author(s):  
Frederick J. Mayer
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Model ◽  
Dark Sector

This brief communication considers and illustrates dark matter and dark energy within the Baryon Phase Transition (BPT) cosmological model as well as some experiments that may confirm (or deny) the validity of the model.

scholarly journals Observational challenges for the standard FLRW model

2016 ◽  
Vol 25 (03) ◽  
pp. 1630007 ◽  
Author(s):  
Thomas Buchert ◽  
Alan A. Coley ◽  
Hagen Kleinert ◽  
Boudewijn F. Roukema ◽  
David L. Wiltshire
Keyword(s):  
General Relativity ◽  
Cosmological Model ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Parallel Session

In this paper, we summarize some of the main observational challenges for the standard Friedmann–Lemaître–Robertson–Walker (FLRW) cosmological model and describe how results recently presented in the parallel session “Large-scale Structure and Statistics” (DE3) at the “Fourteenth Marcel Grossman Meeting on General Relativity” are related to these challenges.

scholarly journals Observational constraints of a new unified dark fluid and the H0 tension

2019 ◽  
Vol 490 (2) ◽  
pp. 2071-2085 ◽  
Author(s):  
Weiqiang Yang ◽  
Supriya Pan ◽  
Andronikos Paliathanasis ◽  
Subir Ghosh ◽  
Yabo Wu
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Early Time ◽  
Observational Constraints ◽  
Minimal Extension ◽  
Energy Evolution ◽  
The Universe ◽  
Different Sources

ABSTRACT Unified cosmological models have received a lot of attention in astrophysics community for explaining both the dark matter and dark energy evolution. The Chaplygin cosmologies, a well-known name in this group have been investigated matched with observations from different sources. Obviously, Chaplygin cosmologies have to obey restrictions in order to be consistent with the observational data. As a consequence, alternative unified models, differing from Chaplygin model, are of special interest. In the present work, we consider a specific example of such a unified cosmological model, that is quantified by only a single parameter μ, that can be considered as a minimal extension of the Λ-cold dark matter cosmology. We investigate its observational boundaries together with an analysis of the universe at large scale. Our study shows that at early time the model behaves like a dust, and as time evolves, it mimics a dark energy fluid depicting a clear transition from the early decelerating phase to the late cosmic accelerating phase. Finally, the model approaches the cosmological constant boundary in an asymptotic manner. We remark that for the present unified model, the estimations of H0 are slightly higher than its local estimation and thus alleviating the H0 tension.

How Far Do They Go? The Outer Structure of Galactic Dark Matter Halos

2006 ◽  
Vol 645 (2) ◽  
pp. 1001-1011 ◽  
Author(s):  
Francisco Prada ◽  
Anatoly A. Klypin ◽  
Eduardo Simonneau ◽  
Juan Betancort‐Rijo ◽  
Santiago Patiri ◽  
...  
Keyword(s):  
Dark Matter ◽  
Dark Matter Halos ◽  
Galactic Dark Matter

scholarly journals Large-scale assembly bias of dark matter halos

2017 ◽  
Vol 2017 (03) ◽  
pp. 059-059 ◽  
Author(s):  
Titouan Lazeyras ◽  
Marcello Musso ◽  
Fabian Schmidt
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Dark Matter Halos

scholarly journals On galaxy rotation curves from a continuum mechanics approach to modified gravity

2018 ◽  
Vol 27 (02) ◽  
pp. 1850007 ◽  
Author(s):  
Christian G. Böhmer ◽  
Nicola Tamanini ◽  
Matthew Wright
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Continuum Mechanics ◽  
Modified Gravity ◽  
Galactic Rotation ◽  
Dark Matter Halos ◽  
Additional Structure ◽  
Rotation Curves ◽  
Small Deviations ◽  
Galaxy Rotation Curves

We consider a modification of General Relativity motivated by the treatment of anisotropies in Continuum Mechanics. The Newtonian limit of the theory is formulated and applied to galactic rotation curves. By assuming that the additional structure of spacetime behaves like a Newtonian gravitational potential for small deviations from isotropy, we are able to recover the Navarro–Frenk–White profile of dark matter halos by a suitable identification of constants. We consider the Burkert profile in the context of our model and also discuss rotation curves more generally.

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