The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parameterization of the Big Bang cosmological model in which the universe contains three major components: first, a cosmological constant denoted by Lambda (Greek Λ) and associated with dark energy; second, the postulated cold dark matter (abbreviated CDM); and third, ordinary matter. It is frequently referred to as the standard model of Big Bang cosmology because it is the simplest model that provides a reasonably good account of the following properties of the cosmos:
the existence and structure of the cosmic microwave background
the large-scale structure in the distribution of galaxies
the observed abundances of hydrogen (including deuterium), helium, and lithium
the accelerating expansion of the universe observed in the light from distant galaxies and supernovaeThe model assumes that general relativity is the correct theory of gravity on cosmological scales. It emerged in the late 1990s as a concordance cosmology, after a period of time when disparate observed properties of the universe appeared mutually inconsistent, and there was no consensus on the makeup of the energy density of the universe.
The ΛCDM model can be extended by adding cosmological inflation, quintessence and other elements that are current areas of speculation and research in cosmology.
Some alternative models challenge the assumptions of the ΛCDM model. Examples of these are modified Newtonian dynamics, entropic gravity, modified gravity, theories of large-scale variations in the matter density of the universe, bimetric gravity, scale invariance of empty space, and decaying dark matter (DDM).
I’ve been reading about LCDM and MOND recently. And there have been reports of galaxies with little dark matter. I know the lack of dark matter in NGC1052-DF2 was shown not true afterwards. But if such a galaxy without dark matter is actually discovered, would this be sufficient to disprove MOND?
I am trying to find the comoving distance,
$$\chi = c\int_0^z \frac{dz}{H(z)}$$ for the ##\Lambda##CDM model (spatially flat universe, containing only matter and ##\Lambda##).
$$H^2 = H_0^2[\Omega_{m,0}(1+z)^3 + \Omega_{\Lambda, 0}]$$
When I put this into integral I am getting,
$$\chi =...
$$1 - \Omega_{tot} = \Omega_κ = \frac{-κc^2}{R_0^2H_0^2} $$
For ##\Omega_κ=-0.0438## we get a some value for ##R_0##. This ##R_0## is the radius of the observable universe right ?
Not the universe ?
As I understand it, time runs backwards inside a black hole. If the universe were far denser than a black hole when the universe was a fraction of a second old, then how did physical processes ever move forward? That is, how can a clock advance in something as dense as the initial universe?
In 2005, A. Vikhlinin et al. made a hydrostatic equilibrium study - https://arxiv.org/abs/astro-ph/0507092 - of some dozen galaxy clusters. These hydrostatic studies are useful because they don't contain the M/L assumptions of other methods. From this document, I'm trying to extract the dark...
BBN is believed to have started a few tenths of a second after the big bang when temperatures were roughly 116 GK, and lasted until the universe had cooled to about 1.16 GK. According to the FLRW metric, this was about 16 minutes.
I get the impression that the duration is important, but don't...
Greetings,
I am slightly curious as to whether the LCDM model may require a slight tweaking. The reason I am curious is because I recall reading a while back that removing the homogeneity assumption from our current models could assist in accounting for some of the large-scale structures, and...
I noticed this in the arxivs, i thought the LCDM model was irifutable but it seems some are trying to better it.
arXiv:1602.02103 [pdf, ps, other]
First evidence of running cosmic vacuum: challenging the concordance model
Joan Sola, Adria Gomez-Valent, Javier de Cruz Perez
Comments: LaTeX, 6...
Whats the best value of ##Ω_k## (Considering Planck 2015 results).I asked best value cause If you think our universe can be also hyperbolic so ##Ω_k## can be different then 1.
I remember the relationship between ##Ω_k## and k is
##Ω_k=-k/a(t)h^2## or some sort of something like that.k is zero I...
Not according to this paper. arXiv:1507.08279 [pdf, ps, other]
A Test of Cosmological Models using high-z Measurements of H(z)
Fulvio Melia, Thomas M. McClintock
Comments: 22 pages, 1 figure, 1 table. Accepted for publication in the Astronomical Journal
Subjects: Cosmology and Nongalactic...
If we restrict ourselves to a homogeneous, spatially flat LCDM universe model, the Friedman equations can be written a very simple form. Marcus posted several threads in a collaborative effort to develop the simplified approach. Here is a summary of the parts that seem the most informative, to...
My understanding is that the degree of flatness observed for the spatial universe is quite extraordinary, to the extent of begging for an explanation.
If this is correct, then my question is, what are the (most) plausible mechanisms being considered as an explanation for either an exact, or...
From what i have read, right or wrong, there seems to be an universe (age) problem for modern cosmologists,
This is the best paper i have found on the subject.
http://arxiv.org/pdf/1402.6433v3.pdf
Abstract Many dark energy models fail to pass the cosmic age test. In this paper, we investigate...
This paper, http://arxiv.org/abs/1401.7438, proposes a method to falsify the LCDM model based on the BigBOSS project currently under development at UC Berkely. The LCDM model would be under serious stress if dark energy proves suspect. In a nutshell, from...
This paper - The Local Void: for or against ΛCDM?,http://arxiv.org/abs/1401.6459 - puts to the test the question of low galaxy counts in the vicinity of the Milky Way. It has been suggested this poses a problem for LCDM. Using the Millennium II supercomputer at the Max Planck Supercomputer...
This paper; 'What have we learned from observational cosmology ?', http://arxiv.org/abs/1304.4446, provides a good overview on the evidence supporting the LCDM model and why it is currently favored by mainstream scientists. It also offers considerable discussion on the motivation for Dark Matter...
Hi,
I am trying to get a better understanding of the mass distribution as described by the LCDM cosmological model and data that might be more anchored in observation. What I mean by this is that the LCDM model appears to operate on the assumption of the large-scale homogeneity of the universe...
A paper written by Authors: Rong-Jia Yang, Shuang Nan Zhang, published in Mon. Not. R. Astron. Soc. 000, 1–7 (2009) and modified on today's Physics ArXiv asks a question we have looked at before on PF, "Is there an age problem in the early universe of the \LambdaCDM model?"
At high red shift...
[37] arXiv:0811.4684 [ps, pdf, other]
Title: Six Puzzles for LCDM Cosmology
Authors: L. Perivolaropoulos
Comments: 9 pages, 3 figures. Invited article to the TSPU anniversary volume "The Problems of Modern Cosmology" on the occasion of the 50th birthday of Prof. S. D. Odintsov
Subjects...
Is there an article about the Newtonian limit of LCDM?
The LCDM vacuum is deSitter not Minkowski and they have to expand around that so I think nonzero cosmological constant will make a difference. Give references if you know anything.
A couple of things to start with. I'm going to put forward some questions I need help understanding surrounding VSL. I'm not anti-LCDM or against inflation/etc. I'm just interested in the mechanisms of setting up a 'new' theory (I'm aware Einstein delved into VSL, and subsequently disregarded...