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Complete solution of the ΛCDM model problems

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petergreen
#1
Feb4-13, 09:39 AM
P: 25
Introduction: A new cosmology based on the production of massless particles (in the early de Sitter phase) and ΛCDM particles (in the transition to a late time de Sitter stage) has been discussed. The same mechanism avoids the initial singularity, particle horizon and the late time coincidence problem of the ΛCDM model has been phenomenologically eliminated (Λ ≡ 0) because there is no dark energy in accelerating scenario. In particular, this means that the dark energy component may be only a “mirage” (an effective description), since it can be mimicked (globally and locally) by the gravitationally induced particle production mechanism acting in the evolving Universe.

Published in Phys. Rev. D 86, 103534 (2012) [11 pages]
http://link.aps.org/doi/10.1103/PhysRevD.86.103534
http://arxiv.org/pdf/1205.0868.pdf

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Mordred
#2
Feb4-13, 01:52 PM
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sounds similar to this paper I had posted in an older thread.
http://arxiv.org/pdf/1212.1110v1.pdf
petergreen
#3
Feb4-13, 02:51 PM
P: 25
sounds similar to this paper I had posted in an older thread.
http://arxiv.org/pdf/1212.1110v1.pdf
The Magain model curves does not fit for the ΛCDM model and Ia supernova events:



While the Lima CCDM model curve fits for the ΛCDM cosmology:



And this explains the nature and formation of the dark matter.

Mordred
#4
Feb4-13, 04:27 PM
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Complete solution of the ΛCDM model problems

Last I heard ACDM had a 95% confidence level when looking at the large scale structure observations. OCDM had a similar confidence level, however ACDM had a larger confidence level than OCDM.
Not being too familiar with these models, Does this paper you posted increase those confidence levels?

Keep in mind the papers I had on this subject were older lol
Chalnoth
#5
Feb5-13, 06:46 AM
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Quote Quote by Mordred View Post
Last I heard ACDM had a 95% confidence level when looking at the large scale structure observations. OCDM had a similar confidence level, however ACDM had a larger confidence level than OCDM.
Not being too familiar with these models, Does this paper you posted increase those confidence levels?

Keep in mind the papers I had on this subject were older lol
What do you mean? Where did you get this from? And what do you mean by ACDM? Or did you mean ΛCDM?
Jorrie
#6
Feb5-13, 07:18 AM
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Quote Quote by Mordred View Post
Last I heard ACDM had a 95% confidence level when looking at the large scale structure observations. OCDM had a similar confidence level, however ACDM had a larger confidence level than OCDM.
Are you referring to ΛCDM and CCDM (Creation of CDM), or what do the acronyms stand for?

Edit: sorry did not see Chalnoth's
Mordred
#7
Feb5-13, 09:14 AM
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The reference was from this paper

http://arxiv.org/pdf/astro-ph/0005476v1.pdf and yes I meant ΛCDM. I know what the terminology stands for just haven't figured out how to apply symbols that aren't on the quick symbol bar. In regards to the various cosmology models I'm still learning the subtle differences between them. Its quite a daunting task lol.

As far as I understand it the ΛCDM model is the most accurate to other models such as OCDM, CHDM, TCDM and ΛCHDM. Are these other models now invalidated ? The other question I had is does the OP's paper address some of the inaccuracies described in the paper I posted to increase its accuracy in the model.
The reason I'm asking is several of the cosmology text books I have are older but I'm currently studying them. There has been several sections I've found that new data has changed compared to what I have in those text books. The text I have is printed in 2006. Part of my self training in the math has been applying those new values to the provided formulas.
Naty1
#8
Feb5-13, 02:20 PM
P: 5,632
petergreen..thanks for the paper.....
I don't know all the math, but I like the conceptual framework:

from THE FINAL REMARKS [Arxiv]

[This is] A new cosmology based on the production of massless particles (in the early de Sitter phase) and CDM particles (in the transition to a late time de Sitter stage) has been discussed......The same mechanism avoids the initial singularity, particle horizon and .... there is no dark energy in our accelerating scenario..., the model has two extreme accelerating phases (very early and late time de Sitter phases) powered by the same mechanism (particle creation)...We stress that our model provides a natural solution to the horizon problem and finally it connects smoothly the radiation and the matter dominated eras, respectively. At late times it also mimics perfectly the cosmic expansion history of the concordance ΛCDM model... In particular, this means that studies involving the gas mass fraction may provide a crucial test of our scenario, potentially, modifying our present view of the dark sector. Some investigations along the above discussed lines are in progress and will be published elsewhere.
Is this approach smoother [therefore more natural?] than a ΛCDM model with inflation glued on the front end and a slow roll glued on that to stop inflation?

edit: oops..I also wanted to post this from the Arxiv paper:
"the merits of the particle creation scenario with respect to the usual DE ideology are a) the former has a strong physical basis namely nonequilibrium thermodynamics, while the latter (DE) has not and b) the particle creation mechanism unifies the dark sector (dark energy and dark matter), since a single dark component (the dark matter) needs to be introduced into the cosmic fluid and thus it contains only one free parameter. "

Do you experts agree on the 'strong physical basis...thermodynamics"??....that would seem to be a big deal....

When does the " unstable de Sitter dominated phase" begin and do they explain how it got there??
Chalnoth
#9
Feb5-13, 02:22 PM
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Quote Quote by Mordred View Post
The reference was from this paper

http://arxiv.org/pdf/astro-ph/0005476v1.pdf and yes I meant ΛCDM. I know what the terminology stands for just haven't figured out how to apply symbols that aren't on the quick symbol bar.
Usually the shorthand way of writing this in only English characters is LCDM :)

As for me, I copied and pasted from the Windows character map.

Anyway, I think the main reason I was confused is that I did not understand your terminology. The way the paper states it is the way it's normally stated:
"Current large-scale structure data cannot rule out any of those models at 95% confidence."

That is to say, we never really are able to gain a probability value for the chance that a model is correct. The most we can do is continue to gather more and more experimental evidence that fails to show it incorrect. This paper shows that none of the large scale structure data is inconsistent with the standard cosmology or minor modifications of the standard cosmology.

One can argue that we simply don't yet have enough data to show the problems of these models. But we now have enough independent sets of data to be sure that at the very least, the overall picture of ΛCDM is broadly correct, even if some details need to be changed.

Quote Quote by Mordred View Post
As far as I understand it the ΛCDM model is the most accurate to other models such as OCDM, CHDM, TCDM and ΛCHDM.
ΛCDM is the simplest that remains consistent with the data, not the most accurate (generally if you add extra parameters, you tend to get a better fit to the data). But yes, a universe without dark energy and one with hot dark matter are ruled out. I'm not familiar with Tilted Cold Dark Matter.
Naty1
#10
Feb5-13, 02:48 PM
P: 5,632
As for me, I copied and pasted from the Windows character map.
How do I find that??
petergreen
#11
Feb5-13, 02:55 PM
P: 25
petergreen..thanks for the paper.....
Not at all!
Mordred
#12
Feb5-13, 04:57 PM
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Thanks Chalnoth that helps out quite a bit.
Chalnoth
#13
Feb5-13, 07:51 PM
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Quote Quote by Naty1 View Post
How do I find that??
If you are using Windows, just click the start menu icon and type, "character" and it should find the Character Map program. It's not the best program in the world, but you can find the Greek capital letters quickly by searching for, "Greek Capital".


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