scholarly journals Distinguishing between the inhomogeneous model and ΛCDM model with cosmic age method

2014 ◽  
Vol 733 ◽  
pp. 69-75 ◽  
Author(s):  
Siqi Liu ◽  
Tong-Jie Zhang
Keyword(s):  
Inhomogeneous Model ◽  
Λcdm Model

An homogeneous growth model of gallium arsenide epitaxial layers from the gas phase

1989 ◽  
Vol 54 (11) ◽  
pp. 2933-2950
Author(s):  
Emerich Erdös ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma
Keyword(s):  
Experimental Data ◽  
Gallium Arsenide ◽  
Kinetic Study ◽  
Gas Phase ◽  
Growth Model ◽  
Epitaxial Layers ◽  
Inhomogeneous Model ◽  
Homogeneous Models ◽  
Active Centres

This paper represents a continuation and ending of the kinetic study of the gallium arsenide formation, where a so-called inhomogeneous model is proposed and quantitatively formulated in five variants, in which two kinds of active centres appear. This model is compared both with the experimental data and with the previous sequence of homogeneous models.

scholarly journals Testing the effect of H0 on fσ8 tension using a Gaussian Process method

2020 ◽  
Author(s):  
En-Kun Li ◽  
Minghui Du ◽  
Zhi-Huan Zhou ◽  
Hongchao Zhang ◽  
Lixin Xu
Keyword(s):  
Growth Rate ◽  
Dark Energy ◽  
Cosmological Constant ◽  
Gaussian Process ◽  
Dark Energy Model ◽  
Hubble Space Telescope ◽  
Λcdm Model ◽  
Space Distortion ◽  
Best Fit ◽  
Process Method

Abstract Using the fσ8(z) redshift space distortion (RSD) data, the $\sigma _8^0-\Omega _m^0$ tension is studied utilizing a parameterization of growth rate f(z) = Ωm(z)γ. Here, f(z) is derived from the expansion history H(z) which is reconstructed from the observational Hubble data applying the Gaussian Process method. It is found that different priors of H0 have great influences on the evolution curve of H(z) and the constraint of $\sigma _8^0-\Omega _m^0$. When using a larger H0 prior, the low redshifts H(z) deviate significantly from that of the ΛCDM model, which indicates that a dark energy model different from the cosmological constant can help to relax the H0 tension problem. The tension between our best-fit values of $\sigma _8^0-\Omega _m^0$ and that of the Planck 2018 ΛCDM (PLA) will disappear (less than 1σ) when taking a prior for H0 obtained from PLA. Moreover, the tension exceeds 2σ level when applying the prior H0 = 73.52 ± 1.62 km/s/Mpc resulted from the Hubble Space Telescope photometry. By comparing the $S_8 -\Omega _m^0$ planes of our method with the results from KV450+DES-Y1, we find that using our method and applying the RSD data may be helpful to break the parameter degeneracies.

scholarly journals Estimate of energy constituents of the universe in ΛCDM

2017 ◽  
Vol 95 (1) ◽  
pp. 21-24
Author(s):  
Jung-Jeng Huang ◽  
Meng-Jong Wang
Keyword(s):  
Maximal Entropy ◽  
Extended Version ◽  
Cosmic Scale ◽  
Λcdm Model ◽  
The Universe ◽  
Entropy Of The Universe

We propose that the Hubble law can be viewed as the de Broglie relation on a cosmic scale. We show how the entropy of the Universe can be estimated in the ΛCDM model and its extended version, and how the quest for the maximal entropy leads to the energy constituents of the current Universe.

scholarly journals Analysing dissipative effects in the ΛCDM model

2018 ◽  
Vol 2018 (12) ◽  
pp. 017-017 ◽  
Author(s):  
Norman Cruz ◽  
Esteban González ◽  
Samuel Lepe ◽  
Diego Sáez-Chillón Gómez
Keyword(s):  
Dissipative Effects ◽  
Λcdm Model

ΛCDM COSMOLOGY THROUGH THE LENS OF EINSTEIN'S STATIC UNIVERSE, THE MOTHER OF Λ

2013 ◽  
Vol 22 (03) ◽  
pp. 1350012 ◽  
Author(s):  
ABHAS MITRA ◽  
S. BHATTACHARYYA ◽  
NILAY BHATT
Keyword(s):  
Dark Energy ◽  
Milky Way ◽  
Fundamental Constant ◽  
Matter Density ◽  
Accelerated Expansion ◽  
Independent Manner ◽  
Static Universe ◽  
Spacetime Geometry ◽  
Λcdm Model ◽  
Do So

We show here that, in the context of Einstein's static universe (ESU), the static cosmological constant Λs = 0. We do so by extending (and not contradicting) the ESU relationship from Λs = 4πρ to Λs = 4πρ = 0, where ρ is the ESU matter density (G = c = 1). This extension follows from the fact that the elements of the spacetime geometry depend on pressure and energy density (ρ). Note in the ΛCDM model, Λ is associated with "Dark Energy (DE)." And, if Λ would be considered as a fundamental constant, it should be zero even for a dynamic universe. In such a case, the observed accelerated expansion could be an artifact of inhomogeneity [D. L. Wiltshire, Phys. Rev. D80 (2009) 123512; E. W. Kolb, Class. Quantum. Grav.28 (2011) 164009] or large peculiar acceleration of the Milky way [C. Tasgas, Phys. Rev. D84 (2011) 063503] or extinction of light of distant supernovae [R. E. Schild and M. Dekker, Astron. Nachr.327 (2006) 729, arXiv:astro-ph/0512236]. The same conclusion has also been obtained in an independent manner [A. Mitra, JCAP03 (2013) 007, doi: 10.1088/1475-7516/2013/03/007].

GROWTH INDEX AND MODIFIED GRAVITY

2011 ◽  
Vol 01 ◽  
pp. 228-233
Author(s):  
YUNGUI GONG
Keyword(s):  
Growth Rate ◽  
Dark Energy ◽  
Modified Gravity ◽  
Growth Index ◽  
Accurate Approximation ◽  
Energy Models ◽  
Λcdm Model ◽  
The Universe ◽  
Matter Energy ◽  
Matter Perturbation

The growth rate of matter perturbation and the expansion rate of the Universe can be used to distinguish modified gravity and dark energy models. Remarkably, the growth rate can be approximated as Ωγ. We discuss the dependence of the growth index γ on the dimensionless matter energy density Ω for a more accurate approximation of the growth factor. The observational data are used to fit different models. The data strongly disfavor the Dvali-Gabadadze-Porrati model. For the ΛCDM model, we find that [Formula: see text]. For the Dvali-Gabadadze-Porrati model, we find that [Formula: see text].

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.

scholarly journals Fermi Degenerate Antineutrino Star Model of Dark Energy

2020 ◽  
Vol 2020 ◽  
pp. 1-11 ◽  
Author(s):  
Tom F. Neiser
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Background Radiation ◽  
Mass Density ◽  
High Energy ◽  
Big Bang ◽  
Gravitational Mass ◽  
High Energy Density ◽  
Star Model ◽  
Λcdm Model

When the Large Hadron Collider resumes operations in 2021, several experiments will directly measure the motion of antihydrogen in free fall for the first time. Our current understanding of the universe is not yet fully prepared for the possibility that antimatter has negative gravitational mass. This paper proposes a model of cosmology, where the state of high energy density of the big bang is created by the collapse of an antineutrino star that has exceeded its Chandrasekhar limit. To allow the first neutrino stars and antineutrino stars to form naturally from an initial quantum vacuum state, it helps to assume that antimatter has negative gravitational mass. This assumption may also be helpful to identify dark energy. The degenerate remnant of an antineutrino star can today have an average mass density that is similar to the dark energy density of the ΛCDM model. When in hydrostatic equilibrium, this antineutrino star remnant can emit isothermal cosmic microwave background radiation and accelerate matter radially. This model and the ΛCDM model are in similar quantitative agreement with supernova distance measurements. Therefore, this model is useful as a purely academic exercise and as preparation for possible future discoveries.

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