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A possible Coasting Universe model vs ΛCDM 
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#1
Feb613, 12:09 PM

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Two Coasting Universe model and comparison of the ΛCDM as well as Rh = ct models with Ia supernovae, GMB and CMB events. Both theory lead to the same result and fundamentals.
[Journal references below] First model: Rh = ct universe "The backbone of standard cosmology is the FriedmannRobertsonWalker solution to Einstein’s equations of general relativity (GR). In recent years, observations have largely confirmed many of the properties of this model, which is based on a partitioning of the universe’s energy density into three primary constituents: matter, radiation, and a hypothesized dark energy which, in ΛCDM, is assumed to be a cosmological constant Λ. Yet with this progress, several unpalatable coincidences (perhaps even inconsistencies) have emerged along with the successful confirmation of expected features. One of these is the observed equality of our gravitational horizon Rh(t0) with the distance ct0 light has traveled since the big bang, in terms of the current age t0 of the universe. This equality is very peculiar because it need not have occurred at all and, if it did, should only have happened once (right now) in the context of ΛCDM. In this paper, we propose an explantion for why this equality may actually be required by GR, through the application of Birkhoff’s theorem and the Weyl postulate, at least in the case of a flat spacetime. If this proposal is correct, Rh(t) should be equal to ct for all cosmic time t, not just its present value t0. Therefore models such as ΛCDM would be incomplete because they ascribe the cosmic expansion to variable conditions not consistent with this relativistic constraint. We show that this may be the reason why the observed galaxy correlation function is not consistent with the predictions of the standard model. We suggest that an Rh = ct universe is easily distinguishable from all other models at large redshift (i.e., in the early universe), where the latter all predict a rapid deceleration." The R_{h} = ct Universe http://arxiv.org/pdf/1109.5189.pdf Fitting the Union2.1 SN Sample with the R_{h} = ct Universe http://arxiv.org/pdf/1206.6289.pdf The R_{h} = ct Universe Without Inflation http://arxiv.org/pdf/1206.6527.pdf Angular Correlation of the CMB in the R_{h} = ct Universe http://arxiv.org/pdf/1207.0015.pdf HighZ Quasars in the R_{h} = ct Universe http://arxiv.org/pdf/1301.0017.pdf The GammaRay Burst Hubble Diagram and Its Cosmological Implications http://arxiv.org/pdf/1301.0894.pdf [Journal refs.: Monthly Notices of the Royal Astronomical Society (MNRAS) & Astronomical Journal  IOP Science] Second model: The model of a flat (Euclidean) expansive homogeneous and isotropic relativistic universe in the light of the general relativity, quantum mechanics, and observations "Assuming that the relativistic universe is homogeneous and isotropic, we can unambiguously determine its model and physical properties, which correspond with the Einstein general theory of relativity (and with its two special partial solutions: Einstein special theory of relativity and Newton gravitation theory), quantum mechanics, and observations, too." http://arxiv.org/pdf/1301.0894.pdf [Journal ref.: Astrophysics and Space Science] The two theory fundamentals: 


#3
Feb613, 05:52 PM

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PF Gold
P: 3,274

I have argued for the benefits of the coasting cosmological model in the past.
Viz: 1. No need for Inflation; the horizon, density and smoothness problems that Inflation was developed to explain would not be there in the first place. 2. A natural explanation for the Age of the Universe = Hubble Time coincidence. 3. It alleviates any Age problem in the early universe. 4. The longer BBN epoch yields results in a higher baryon density that may explain Dark Matter as baryonic in nature. ( Must still be dark in the form of IMBHs perhaps). It would leave a Deuterium problem but resolve the Lithium Problem. 5. It would explain a low power deficiency in the CMB power spectrum when compared with the LCDM prediction. First proposed by Kolb in 1989 as a way of avoiding Inflation A coasting cosmology , it was then taken up by an Indian team who found it a concordant alternative to LCDM. A Concordant “Freely Coasting” Cosmology, recently it has been advocated by Melia et al. in the papers cited in the OP. There are problems, but no more than the standard model that has had to invoke Inflation, DM and DE, all unconfirmed in the laboratory. Just a thought, Garth 


#4
Feb613, 06:19 PM

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A possible Coasting Universe model vs ΛCDM



#5
Feb713, 08:43 AM

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#6
Feb713, 10:22 AM

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PF Gold
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Linear expansion requires DE with an equation of state [itex]\omega =  \frac{1}{3}[/itex]. Kolb suggested K matter with [itex] p_k =  \frac{1}{3} \rho_k[/itex] Such as might be provided by cosmic string networks. As for an entirely new law of gravity, Self Creation Cosmology maybe?? (published in 'Horizons in World Physics, Volume 247: New Developments in Quantum Cosmology Research', Nova Science Publishers, Inc. New York) Just a thought... Garth 


#7
Feb713, 12:11 PM

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I don't think you can fit the coasting universe with the CMB, at all. 


#8
Feb713, 04:57 PM

P: 25

Dear Chalnoth and Garth!
In the coasting universe, dark energy does not exist (Λ=0)! Only dark matter, onto which is the only possible candidate the weakly interacting axion, or the continuously and in increasing quantities generated, appearing and disappearing virtual particle pairs. 


#9
Feb713, 05:11 PM

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PF Gold
P: 3,274

The empty universe, the Milne FRW model, contains no source of gravitation and therefore there is nothing to decelerate it, so it expands linearly. If matter is present (as indeed there is) then that produces a gravitational field that would decelerate the universe. To obtain linear expansion something must counter act this effect. In the DiracMilne universe equal amounts of matter and antimatter exist and it is assumed that they repel each other. The universe instantly separates out into matter and antimatter zones and this mutual repulsion cancels out the gravitational attraction within each zone. Otherwise you need a medium of high negative pressure, otherwise known as dark energy and they are several hypothetical candidates that might be the source of this, the cosmological constant being one of them. I hope this helps. Garth 


#10
Feb713, 05:29 PM

P: 25

Garth!
Here the negative energy is the gravitational energy! The zeroenergy universe hypothesis states that the total amount of energy in the universe is exactly zero. The positive energy of the matter is exactly balanced by the negative energy of the gravitational field. If in an expansive Universe relativistic and quantummechanical properties are complementary, permanent constant maximum possible increase of negative energy of gravitational field must arise and simultaneously, permanent constant maximum possible increase of positive energy of the matter must occur, which compensate each other; hence, total energy of the Universe is equal to zero. Therefore, the expanding Universe must be nondecelerative and nonaccelerative, i.e., during the whole expansive evolution phase, it must expand by constant maximum possible velocity v = c. So the universe expands linearly. 


#11
Feb713, 06:03 PM

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PF Gold
P: 3,274

The expansion rate is determined by the FRW equation in which curvature effects and expansion rates are convoluted. You have to solve the equations carefully and use the equation of state to separate out the two effects. It is possible to balance the eos using a certain amount of cosmological constant, (which I take to be a form of DE) but you then have to show that that model is observationally concordant. It here that Chalnoth and I disagree. Garth 


#12
Feb713, 06:46 PM

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There still may be some cosmic strings, but they don't make up a significant fraction of the energy density of the universe. 


#13
Feb713, 06:59 PM

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#14
Feb713, 07:10 PM

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http://lambda.gsfc.nasa.gov/product/..._anomalies.pdf And the main discrepancy between the coasting universe and ΛCDM is likely to be found in the power spectrum, which is not shown in the above paper. 


#15
Feb813, 01:46 AM

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PF Gold
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Observational Constraints of a MatterAntimatter Symmetric Milne Universe A Concordant “Freely Coasting” Cosmology 


#16
Feb813, 08:46 AM

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