scholarly journals Universe opacity and Type Ia supernova dimming

2019 ◽  
Vol 489 (1) ◽  
pp. L63-L68 ◽  
Author(s):  
Václav Vavryčuk
Keyword(s):  
Cold Dark Matter ◽  
Hubble Constant ◽  
Light Extinction ◽  
Universe Model ◽  
Type Ia Supernova ◽  
Accelerating Expansion ◽  
Λcdm Model ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
The Universe

ABSTRACT In this paper, I revoke a debate about an origin of Type Ia supernova (SN Ia) dimming. I argue that except for a commonly accepted accelerating expansion of the Universe, a conceivable alternative for explaining this observation is universe opacity caused by light extinction by intergalactic dust, even though it is commonly assumed that this effect is negligible. Using data of the Union2.1 SN Ia compilation, I find that the standard Λ cold dark matter (ΛCDM) model and the opaque universe model fit the SN Ia measurements at redshifts z < 1.4 comparably well. The optimum solution for the opaque universe model is characterized by the B-band intergalactic opacity $\lambda _{B} = 0.10 \pm 0.03 \, \mathrm{Gpc}^{-1}$ and the Hubble constant $H_0 = 68.0 \pm 2.5 \, \mathrm{km\, s^{-1}\, Mpc^{-1}}$. The intergalactic opacity is higher than that obtained from independent observations but still within acceptable limits. This result emphasizes that the issue of the accelerating expansion of the Universe as the origin of the SN Ia dimming is not yet definitely resolved. Obviously, the opaque universe model as an alternative to the ΛCDM model is attractive, because it avoids puzzles and controversies associated with dark energy and the accelerating expansion.

scholarly journals SOLVING THE INVERSE PROBLEM WITH INHOMOGENEOUS UNIVERSES

2011 ◽  
Vol 01 ◽  
pp. 234-239
Author(s):  
CHUL-MOON YOO ◽  
TOMOHIRO KAI ◽  
KEN-ICHI NAKAO
Keyword(s):  
Inverse Problem ◽  
Dark Matter ◽  
Cold Dark Matter ◽  
Big Bang ◽  
Universe Model ◽  
Cosmological Redshift ◽  
Λcdm Model ◽  
The Big Bang ◽  
The Universe ◽  
Dust Universe

We construct the Lemaître-Tolman-Bondi (LTB) dust universe whose distance-redshift relation is equivalent to that in the concordance Λ cold dark matter (ΛCDM) cosmological model. In our model, the density distribution and velocity field are not homogeneous, whereas the big-bang time is uniform, which implies that the universe is homogeneous at its beginning. We also study the temporal variation of the cosmological redshift and show that, by the observation of this quantity, we can distinguish our LTB universe model from the concordance ΛCDM model, even if their redshift-distance relations are equivalent to each other.

scholarly journals BAYESIAN ANALYSIS OF THE CHAPLYGIN GAS AND COSMOLOGICAL CONSTANT MODELS USING THE SNe Ia DATA

2004 ◽  
Vol 13 (04) ◽  
pp. 669-693 ◽  
Author(s):  
R. COLISTETE ◽  
J. C. FABRIS ◽  
S. V. B. GONÇALVES ◽  
P. E. DE SOUZA
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Confidence Level ◽  
Cold Dark Matter ◽  
Chaplygin Gas ◽  
Type Ia Supernovae ◽  
Λcdm Model ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

The type Ia supernovae observational data are used to estimate the parameters of a cosmological model with cold dark matter and the Chaplygin gas. This exotic gas, which is characterized by a negative pressure varying with the inverse of density, represents in this model the dark energy responsible for the acceleration of the Universe. The Chaplygin gas model depends essentially on four parameters: the Hubble constant, the velocity of the sound of the Chaplygin gas, the curvature of the Universe and the fraction density of the Chaplygin gas and the cold dark matter. The Bayesian parameter estimation yields [Formula: see text] and [Formula: see text]. These and other results indicate that a Universe completely dominated by the Chaplygin gas is favoured, what reinforces the idea that the Chaplygin gas may unify the description for dark matter and dark energy, at least as the type Ia supernovae data are concerned. A closed and accelerating Universe is also favoured. The Bayesian statistics indicates that the Chaplygin gas model is more likely than the standard cosmological constant (ΛCDM) model at 55.3% confidence level when an integration on all free parameters is performed. Assuming the spatially flat curvature, this percentage mounts to 65.3%. On the other hand, if the density of dark matter is fixed at zero value, the Chaplygin gas model becomes more preferred than the ΛCDM model at 91.8% confidence level. Finally, the hypothesis of flat Universe and baryonic matter (Ωb0=0.04) implies a Chaplygin gas model preferred over the ΛCDM at a confidence level of 99.4%.

scholarly journals Modified Statistical Analysis of SNe1a Data

2020 ◽  
Vol 240 ◽  
pp. 02001
Author(s):  
Lisa Goh ◽  
Cindy Ng
Keyword(s):  
Profile Likelihood ◽  
Cosmic Acceleration ◽  
Confidence Levels ◽  
Accelerating Expansion ◽  
Original Analysis ◽  
Λcdm Model ◽  
Contour Plots ◽  
Expansion Of The Universe ◽  
Best Fit ◽  
The Universe

We review an improved maximum likelihood analysis of the Type 1a Supernova (SNe1a) data. We calculate the profile likelihood in the Ωm -ΩΛ pa- rameter space by conducting a parameter sweep across the 8 SNe1a parameters, using a Markov Chain Monte Carlo (MCMC) optimization algorithm. This im- proved analysis, which does not assume arbitrary values for the uncertainties, has the advantage of being bias-free as compared to the original analysis. We use the Joint Lightcurve Analysis (JLA) dataset containing 740 SN1a data sam- ples for our study, and compare among 5 different models: the ΛCDM model, the flat wCDM model, its non-flat generalization, as well as two dynamical w(z) parametrizations. We find that the ΛCDM model is favoured over the other models, and the best fit values based on this model are Ωm =0.40 and ΩΛ =0.55. Interestingly, in most of the contour plots we obtain, the line of no acceleration is crossed at 2∼3σ confidence levels, which is similar to the results published by Nielsen et al, the original authors who introduced the improved maximum like- lihood analysis. When we generalize the wCDM model to the dynamical w(z) parametrizations, the evidence for cosmic acceleration becomes even weaker. This raises the question of how secure we can be of an accelerating expansion of the universe.

scholarly journals EXPLAINING THE SUPERNOVA DATA WITHOUT ACCELERATING EXPANSION

2012 ◽  
Vol 21 (11) ◽  
pp. 1242021 ◽  
Author(s):  
W. M. STUCKEY ◽  
T. J. McDEVITT ◽  
M. SILBERSTEIN
Keyword(s):  
General Relativity ◽  
Quantum Gravity ◽  
Cosmological Constant ◽  
Nobel Prize ◽  
De Sitter ◽  
Accelerating Expansion ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
Nobel Prize In Physics ◽  
The Universe

The 2011 Nobel Prize in Physics was awarded "for the discovery of the accelerating expansion of the universe through observations of distant supernovae." However, it is not the case that the type Ia supernova data necessitates accelerating expansion. Since we do not have a successful theory of quantum gravity, we should not assume general relativity (GR) will survive unification intact, especially on cosmological scales where tests are scarce. We provide a simple example of how GR cosmology may be modified to produce a decelerating Einstein-de Sitter cosmology (EdS) that accounts for the Union2 Compilation data as well as the accelerating ΛCDM (EdS plus a cosmological constant).

Is Our Universe Accelerating Dynamics Fractional Order?

2015 ◽  
Author(s):  
Caibin Zeng ◽  
YangQuan Chen ◽  
Igor Podlubny
Keyword(s):  
Fundamental Solution ◽  
Fractional Order ◽  
Exponential Function ◽  
Dynamical Equation ◽  
Hubble Constant ◽  
Expansion Rate ◽  
Fractional Dynamics ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

In this paper, a fractional dynamics approach is used to characterize the observed accelerating expansion of the universe. We claim that the evolution of accelerating expansion obeys an α-exponential function, which is the fundamental solution of linear fractional order dynamical equation. We find that the Hubble constant is 67.8807, 68.2546, and 67.9119 for all redshift z < 1.5, z < 1, and z < 0.1 based on the dataset collected by the Supernova Cosmology Project. Furthermore, we verify that the expansion rate of our universe is speeding up and actually obeys a Mittag-Leffler law.

The Mystery of the Dark Energy Based on Energy Materials

2012 ◽  
Vol 496 ◽  
pp. 523-526
Author(s):  
Jian Guo Lu ◽  
Ming Hu
Keyword(s):  
Dark Energy ◽  
Gamma Ray ◽  
Background Radiation ◽  
Accelerated Expansion ◽  
Energy Materials ◽  
Type Ia Supernova ◽  
Microwave Background Radiation ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
The Universe

Recently the observations on the type Ia supernova has showed the accelerated expansion of the universe which can be used to illustrate by the “dark energy”. In order to understand the accelerated expansion of the universe and the dark energy, people study them based on two aspects: theoretical mechanism and cosmology observation restrictions. The simplest and the most frequently used models of the dark energy are the vacuum energy, cosmic constant model and quintessence model etc. The measurement of the universe can be used to identify the properties of the dark energy. The anisotropy of the type Ia supernova and cosmic microwave background radiation are the methods which commonly used to detect the dark energy, other methods are weak lensing, X ray gas group, high red shift gamma-ray burst and so on

scholarly journals Kinetic studies relating to the accelerated expansion of the Universe

2021 ◽  
Author(s):  
Wei Zhang ◽  
Cheng Deng
Keyword(s):  
General Relativity ◽  
Hubble Constant ◽  
Kinetic Studies ◽  
Physical Significance ◽  
Accelerated Expansion ◽  
Newtonian Mechanics ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Masses ◽  
The Universe

Abstract After taking into account the mass loss of galaxies and stars at the cosmic scale, the speed and acceleration of the accelerating expansion of the Universe are derived from general relativity and Newtonian mechanics, as respectively. The physical significance of the Hubble constant is proved to be the average of the masses ejected per second per unit mass in the observed range, and it is shown that the accelerated expansion of the universe doesn’t require dark energy

scholarly journals CONSTRAINTS ON A NEW ALTERNATIVE MODEL TO DARK ENERGY

2005 ◽  
Vol 14 (09) ◽  
pp. 1495-1506 ◽  
Author(s):  
YUNGUI GONG ◽  
XI-MING CHEN
Keyword(s):  
Dark Energy ◽  
Alternative Model ◽  
Friedmann Equation ◽  
Recent Past ◽  
New Model ◽  
Type Ia Supernova ◽  
The Future ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
The Universe

The recent type Ia supernova data suggest that the Universe is accelerating now and had decelerated in recent past. This may provide the evidence that the standard Friedmann equation needs to be modified. We analyze in detail a new model in the context of modified Friedmann equation using the supernova data published by the High-z Supernova Search Team and the Supernova Cosmology Project. The new model explains recent acceleration and past deceleration. Furthermore, the acceleration of the expansion of the Universe is almost zero in the future.

Built-in inflation in f(G) gravity

2016 ◽  
Vol 25 (01) ◽  
pp. 1650011 ◽  
Author(s):  
M. Sharif ◽  
H. Ismat Fatima
Keyword(s):  
Energy Density ◽  
Late Time ◽  
Universe Model ◽  
Frw Universe ◽  
Eos Parameter ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Bonnet Term

In this paper, we study the role of Gauss–Bonnet term for the early and late time accelerating phases of the universe with the help of two viable [Formula: see text] models in the background of flat FRW universe model. These models show inflationary behavior as well as the present accelerating expansion of the universe. The contribution of Gauss–Bonnet term in pressure and energy density is used to calculate equation of state (EoS) parameter for the modified fluid which behaves like cosmological constant with [Formula: see text]. We discuss early inflation and late accelerating expansion of the universe through scale factor evaluated from equation of continuity numerically.

scholarly journals Taxonomy of Dark Energy Models

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 163
Author(s):  
Verónica Motta ◽  
Miguel A. García-Aspeitia ◽  
Alberto Hernández-Almada ◽  
Juan Magaña ◽  
Tomás Verdugo
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Energy Component ◽  
The Past ◽  
Energy Models ◽  
The Status ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Unknown Component

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

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