scholarly journals Frequency Decay through Electromagnetic Radiation Absorption and Re-Emission by Inter-Galactic Dark Matter as an Alternate Explanation for the Hubble Constant

2016 ◽  
Vol 02 (03) ◽  
pp. 301-311
Author(s):  
David Grant Taylor
Keyword(s):  
Dark Matter ◽  
Electromagnetic Radiation ◽  
Hubble Constant ◽  
Radiation Absorption ◽  
Alternate Explanation ◽  
Galactic Dark Matter

scholarly journals Does the Cosmological Expansion Change Local Dynamics?

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1417
Author(s):  
Marcelo Schiffer
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Hubble Constant ◽  
Matter Content ◽  
Matter Distribution ◽  
Present Value ◽  
Field Equations ◽  
Local Dynamics ◽  
Cosmological Expansion ◽  
Modified Gravity Theories

It is a well-known fact that the Newtonian description of dynamics within Galaxies for its known matter content is in disagreement with the observations as the acceleration approaches a0≈1.2×10−10 m/s2 (slighter larger for clusters). Both the Dark Matter scenario and Modified Gravity Theories (MGT) fail to explain the existence of such an acceleration scale. Motivated by the closeness of the acceleration scale and the Hubble constant cH0≈10−9 h m/s2, we are led to analyze whether this coincidence might have a Cosmological origin for scalar-tensor and spinor-tensor theories by performing detailed calculations for perturbations that represent the local matter distribution on the top of the cosmological background. Then, we solve the field equations for these perturbations in a power series in the present value of the Hubble constant. As we shall see, for both theories, the power expansion contains only even powers in the Hubble constant, a fact that renders the cosmological expansion irrelevant for the local dynamics.

scholarly journals Nanoparticles-decorated coal tar pitch-based carbon foam with enhanced electromagnetic radiation absorption capability

RSC Advances ◽  
2015 ◽  
Vol 5 (26) ◽  
pp. 20256-20264 ◽  
Author(s):  
Rajeev Kumar ◽  
Ashish Gupta ◽  
Sanjay R. Dhakate
Keyword(s):  
Electromagnetic Radiation ◽  
Coal Tar ◽  
Carbon Foam ◽  
Frequency Region ◽  
Radiation Absorption ◽  
Coal Tar Pitch ◽  
Band Frequency ◽  
X Band

Carbon foam decorated with magnetic and dielectric nanoparticles exhibited significantly improved EM radiation absorption in the X-band frequency region.

scholarly journals Is Galactic Dark Matter White?

1999 ◽  
Vol 513 (2) ◽  
pp. L103-L106 ◽  
Author(s):  
G. Chabrier
Keyword(s):  
Dark Matter ◽  
Galactic Dark Matter

scholarly journals CAPTURE OF DARK MATTER BY THE SOLAR SYSTEM

2009 ◽  
Vol 18 (12) ◽  
pp. 1903-1912 ◽  
Author(s):  
I. B. KHRIPLOVICH ◽  
D. L. SHEPELYANSKY
Keyword(s):  
Dark Matter ◽  
Solar System ◽  
Dark Matter Particle ◽  
Matter Density ◽  
Upper And Lower Bounds ◽  
Analytical Estimate ◽  
Upper Limits ◽  
Galactic Dark Matter ◽  
Three Body ◽  
Optimistic Value

We study the capture of galactic dark matter by the solar system. The effect is due to the gravitational three-body interaction between the sun, one of the planets, and a dark matter particle. The analytical estimate for the capture cross-section is derived and the upper and lower bounds for the total mass of the captured dark matter particles are found. The estimates for their density are less reliable. The most optimistic of them gives an enhancement of dark matter density by about three orders of magnitudes compared to its value in our galaxy. However, even this optimistic value remains below the best present observational upper limits by about two orders of magnitude.

scholarly journals Testing the warmness of dark matter

2019 ◽  
Vol 490 (1) ◽  
pp. 1406-1414 ◽  
Author(s):  
Suresh Kumar ◽  
Rafael C Nunes ◽  
Santosh Kumar Yadav
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Hubble Space Telescope ◽  
Hubble Constant ◽  
Mass Scale ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Mean Values ◽  
Λcdm Model ◽  
Cosmological Data

ABSTRACT Dark matter (DM) as a pressureless perfect fluid provides a good fit of the standard Λ cold dark matter (ΛCDM) model to the astrophysical and cosmological data. In this paper, we investigate two extended properties of DM: a possible time dependence of the equation of state of DM via Chevallier–Polarski–Linder parametrization, wdm = wdm0 + wdm1(1 − a), and the constant non-null sound speed $\hat{c}^2_{\rm s,dm}$. We analyse these DM properties on top of the base ΛCDM model by using the data from Planck cosmic microwave background (CMB) temperature and polarization anisotropy, baryonic acoustic oscillations (BAOs), and the local value of the Hubble constant from the Hubble Space Telescope (HST). We find new and robust constraints on the extended free parameters of DM. The most tight constraints are imposed by CMB+BAO data, where the three parameters wdm0, wdm1, and $\hat{c}^2_{\rm s,dm}$ are, respectively, constrained to be less than 1.43 × 10−3, 1.44 × 10−3, and 1.79 × 10−6 at 95 per cent CL. All the extended parameters of DM show consistency with zero at 95 per cent CL, indicating no evidence beyond the CDM paradigm. We notice that the extended properties of DM significantly affect several parameters of the base ΛCDM model. In particular, in all the analyses performed here, we find significantly larger mean values of H0 and lower mean values of σ8 in comparison to the base ΛCDM model. Thus, the well-known H0 and σ8 tensions might be reconciled in the presence of extended DM parameters within the ΛCDM framework. Also, we estimate the warmness of DM particles as well as its mass scale, and find a lower bound: ∼500 eV from our analyses.

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
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