Talk:Lambda-CDM model

message: "This component makes up 26% of the energy density of the present universe. The remaining 4%"
I'm not qualified to fix it, but that sure looks wrong to me...
-Robin
70% are alrady accounted for (Lambda) in the preceding paragraph. --Pjacobi 17:48, 2005 May 4 (UTC)
The latest results from the WMAP probe have estimated these numbers to be, indeed, 74% Dark Energy, 22% Dark Matter, and (still) 4% normal matter. --130.253.135.140 04:57, 5 June 2006 (UTC)
thread_title: Older comments

message: Not to say I understand the rest of it, but the most mysterious phrase in the article is this: "spatial curvature at the level of one part in ten or one hundred thousand". One hundred thousand what? I can kind of picture spatial curvature of 1/10 as the shape of the top of an umbrella in n dimensions, and it probably corresponds to spatial curvature Ωk = 0.086 at the end of the article. But I can't imagine why that picture would be described with the number 100,000, or any other number unrelated to 1/10. Art LaPella 20:45, September 2, 2005 (UTC)
:I may have written that part. Ten or one hundred thousand (Ωk = 10−4 or 10−5) corresponds to the level of spatial curvature predicted by cosmic inflation.  It comes from the fact that inflation will have generated fluctuations that are much larger than the particle horizon and these show up as perturbations in the spatial curvature for the universe. The numerical value comes from the 10−5 amplitude of primordial perturbations produced in inflationary models. –Joke137 23:34, 4 September 2005 (UTC)
replies: text: I think I understand the part I need to. Does that mean you would support this change: "...one part in ten thousand to one hundred thousand"? Or better, "...at the level of 10−4 to 10−5" ? Art LaPella 00:04, September 5, 2005 (UTC)
Absolutely. –Joke137 00:11, 5 September 2005 (UTC)
thread_title: 100,000

message: Values given in the article do not correspond to values given in WMAP. For example, value for Hubble constant says 69.5 ± 4 here, while in the WMAP it's 71 ± 4. Values for the age of Universe are 13.55 and 13.7 Gyr. Values for Ωb, Ωm, ΩΛ, are also different. Where are they correct? 217.114.151.228 18:48, 13 September 2005 (UTC)
replies: text: I strongly assume at both places. In the WMAP article there should be the estimates based on WMAP data alone and here the best concordance estimates (taling into account all data). There are quite lot choices to mix the together (and also to choose which parameters should be estimated an which are fixed), so that there are always some disagreements. --Pjacobi 18:57, 13 September 2005 (UTC)

text: The figures given do not add up but come to more than 100%.  Please check values or have error bars for the figures.  John D. Croft (talk) 14:50, 10 July 2010 (UTC)
thread_title: Parameters section values

message: Should it be at ΛCDM model? Rich   Farmbrough 23:30, 11 December 2005 (UTC)
replies: text: Not without first considering Wikipedia:Naming conventions (use English). Art LaPella 02:48, 12 December 2005 (UTC)
replies: text: ΛCDM is already a REDIRECT. Should be good enough. --Pjacobi 07:43, 12 December 2005 (UTC)
replies: text:  Should it be "Flat Lambda-CDM model"?  If not, then the model should have seven base paramters rather than six, IMO. Spebudmak 06:19, 24 September 2006 (UTC)

text: Well the WMAP papers call it the "Power Law \Lambda CDM" model.  I have also seen it called the "Flat Power Law \Lambda CDM" model.  I think whether it is "the" minimal model depends on how you define the penalty for adding additional parameters.  Take a look at e.g. Table 3 in Spergel et.al. 2006. Spebudmak 18:44, 16 November 2006 (UTC)
thread_title: Page name

message: The article gives lambda 74% (or, later, 73.2%), cold dark matter 22% (or, later, 22.2% dark matter), 4% everything else (or, later, 4.4% just baryons), and from the discussion on the talk page and what I've seen elsewhere that sees to be pretty much accurate and up to date. The pie chart gives lambda 70%, dark matter 25%, which disagrees. I realize that these numbers aren't exactly absolutely known to great precision, but I can't see any good reason for the text and the chart to give differing numbers without explanation.
Also, the pie chart breaks out the remaining 5% into four separate components (free H and He, stars, neutrinos, and heavy elements). If this breakdown is accurate, it would be useful to mention it in the text. (Is it accurate? Don't many heavy elements count as part of stars? Doesn't "dark matter" unqualified include free elements and neutrinos, most of the heavy elements, and even many stars (given the standard MACHO definitions)?
As an unrelated side note, there doesn't seem to be any way to find alternative models from this page. (By this, I mean non-flat, topologically complex, fractal, etc. models; not MOND, plasma cosmology, braneworld, or cosmological theories that may or may not predict different models.) --76.202.58.169 09:43, 28 May 2007 (UTC)
replies: text: I agree, the chart is rubbish, As a rough visual guide it is incorrect (dark matter definitely not represented as 25%), also it occurs in both this article and in the article on dark energy. It'd make sense to have a chart that reflects the proportions in the article and also at least approximates what these look like as a percentage otherwise there's no point having it. Escobar otter (talk) 15:03, 11 March 2008 (UTC)

text: The pie chart is nice, and it provides a useful conceptual way to view the energy balance of the Universe, but the numbers are certainly wrong and have been for quite some time now. The numbers in the table further down the page are what should be in the pie chart. Unless someone can make an updated version of it, I recommend removing it from this, and other pages it is linked to. - Parejkoj (talk) 19:05, 4 August 2011 (UTC)
thread_title:  Pie Chart 

message: Wouldn't it be appropriate to include in this article a section on the ultimate fate of the Universe according to the ΛCDM model? I think many people ask for the current best guess for the fate of the Universe. /129.142.71.166 (talk) 13:19, 8 September 2008 (UTC)
thread_title:  Fate of universe according to ΛCDM 

message: ::It would also be surprising if the temperature of dark matter were absolute zero.
What is the reason for expecting a zero temperature ? Dark matter interacts gravitationally (and propably weakly) with normal matter, though the effect is very small, it should be enough to increase the temperature. Also zero (viral) temperature would mean gravitational collapse and surely the Big Bang would requiere higher temperatures. This sentence is irritating and so I propose to delete it  —Preceding unsigned comment added by 147.142.111.239 (talk) 17:38, 16 June 2009 (UTC)
thread_title:  Temperature of dark matter 

message: Can someone add some information about the development of this model? Who proposed the use of this model for the first time? When? How has this changed along these years? Was it proposed by NASA? An individual cosmologist? A group of cosmologists?George Rodney Maruri Game (talk) 04:04, 20 January 2011 (UTC)
thread_title:  History of Lambda-CDM model 

message: I've added to the article a schematic diagram of the Lambda Cold-dark matter model. This is an artists interpretation of the standard model of big bang cosmology: Concordance model, ΛCDM or Lambda-CDM. The time-line extends from the big bang/inflation era, 13.7 Gyr ago, to the present cosmological time. This diagram attempts to illustrate the accelerated expansion in two-dimensional spherically symmetric form. Both HUDF and COBE images are used, albeit transformed. It is meant as an aid only in the visualization of such a model. Coldcreation (talk) 04:42, 18 May 2012 (UTC)
replies: text: The diagram fails to illustrate where - according to what's stated in the text - the ä=0 takes place. The text suggests at z=0.66, while the diagram puts it at the CMBR, at z=1100. A rather heavy discrepance, I think.... Hilmer B (talk) 20:23, 9 April 2016 (UTC)

text: Another problem with the diagrams like this is that they suggest that the universe is a growing object with boundaries, which supports the popular but incorrect perception that the Big Bang is an "explosion". I think it would be useful to drop the 3D effects and show a 2D grid (one spatial and one temporal dimension) with an infinite-range spatial dimension. The grid should be progressively subdivided in the spatial dimension as the scale factor  increases. Removing the cone outline and including regions outside of the cone would help to show that the Big Bang happened "everywhere". Petr Matas 06:32, 10 April 2016 (UTC)

text: I believe that this image is a reuse of an illustration of a gravitational well, where CMBR happened to replace the surface of a neutron star - or whatever. Standards of Wikipedia should be somewhat higher than this. This image should be removed. Hilmer B (talk) 21:23, 10 April 2016 (UTC)
replies: text: And that is probably why the acceleration at present is so exaggerated. I agree, the image is too misleading and should be removed. Petr Matas 17:36, 11 April 2016 (UTC)
thread_title:  Schematic diagram 

message: A couple of things that could be improved:
*"It is the simplest model that is in general agreement with observed phenomena; however, a small minority of astrophysicists have challenged the validity of the model." -- plenty of astrophysicists have proposed alternatives to ΛCDM.  It's a model that leaves several conspicuously blank spaces, so I think any cosmologist would agree that ΛCDM should eventually be replaced by something more complete.  I'm not sure what it would mean to challenge its validity as such, unless we had somehow incorrectly calculated the properties of a ΛCDM universe (so that a ΛCDM universe is not what we think it is).
*"Historically, the dominant cosmological model previous to the now "standard model" was the Steady State theory, proposed independently in 1948 by H. Bondi & T. Gold and by Fred Hoyle." -- if the standard model means ΛCDM here, then there was a huge gap between steady state and the standard model.  I'm also unconvinced that Hoyle, Bondi, and Gold's steady state was ever really the dominant cosmological model.  It's true that most astronomers two decades before assumed that the universe was unchanging on the largest scales, but that's quite a different thing from the specific steady-state cosmology that Hoyle and others developed.  Their steady state model was from the start an alternative to the Big Bang cosmology.
I would work on fixing these, but I don't have time right now to do it well.  Can help look with sources if someone wants to take it on. --Amble (talk) 17:50, 22 June 2012 (UTC)
replies: text: Definitely agree with the second point. Steady State was the assumption prior to the Hubble et al.'s observations, but it wasn't Hoyle's version. I'm not sure about how to reword the first part; there have been several proposed alternatives, but none of them have gotten significant traction, mostly because LCDM fits the data so well. - Parejkoj (talk) 12:37, 23 June 2012 (UTC)
replies: text: Quintessence is an example of a very popular alternative to ΛCDM.  The term ΛCDM is often used in the sense of "plain-vanilla ΛCDM" without inflation or other features, so I suppose it becomes a matter of terminology whether a particular model is an alternative to ΛCDM or a variety of ΛCDM. --Amble (talk) 15:40, 23 June 2012 (UTC)

text: I've made a first pass at the intro.  Feel free to revert, further edit, etc., with discussion here.  This source may be useful: A. V. Filippenko, The Accelerating Universe and Dark Energy: Evidence from Type IA Supernovae.  Lect. Notes Phys. 646, 191-221 (2004). . --Amble (talk) 16:47, 29 June 2012 (UTC)

text: This is a false claim here. Just because it is a difficult topic does not mean it has this kind of bias.  Your "excessive advocacy bias" claim is mostly irrelevant. Arianewiki1 (talk) 09:22, 1 December 2013 (UTC)
thread_title:  A couple of notes 

message: 18:19, 1 December 2013‎ Parejkoj (talk | contribs)‎ . . (21,275 bytes) (-564)‎ . . (Undo POV pushing CN tags by pseudo-science editor.) (undo | thank) 
User:Parejkoj undid request for citations. Unsupported statements in the article are not self-evident and require proper citation. Orrerysky (talk) 18:40, 1 December 2013 (UTC)
replies: text: The revert was to correct disruptive tag bombing and I support it 100%. jps (talk) 22:33, 1 December 2013 (UTC)
replies: text: I was going to say that we maybe actually did need some citations to that effect, but the first two citations actually are perfect here: Kroupa et al., for the term "concordance cosmology", and Liddle's textbook for why it's the standard model. So, I think we're fine here... - Parejkoj (talk) 00:40, 2 December 2013 (UTC)
thread_title: Citations Needed

message: Hello, I'm normally aroung in the German wikipedia, but I came here for reading something up and I was just puzzled by the following formulation:
 The model includes a single originating event, the "Big Bang" or initial singularity,
 which was not an explosion but the abrupt appearance of expanding space-time 
I think that this formulation is very bad since it states something of "appearance". How can a space-time appear? One should be very careful with such formulations as one gets the impression that someone could have looked from outside and seen the universe "appear". I'd rather say, "come into existence" or something similar. Do you agree? --Ein Zaungast (talk) 21:58, 10 September 2014 (UTC)
replies: text: As far as I know, no "initial singularity" appears in the actual models; it only appears in a notional idealized model which is not actually used. I don't think there is any consensus model of what came before inflation (and I'm not sure there is a consensus model of inflation itself, although there appears to be a widespread agreement that it probably happened). -- Peter Donis <peterdonis@alum.mit.edu> 73.87.40.81 (talk) 02:03, 1 March 2017 (UTC)
thread_title:  Big Bang as "sudden appearance"? 

message: Since the model is supposedly based on general relativity there must be some mathematical background to it which defines and uses the quoted parameters. Where is it?  Since the space is assumed flat it presumably uses the Einstein-de Sitter equations. And then there must be a lot of thermodynamic equations as well. At present it's all a mystery.JFB80 (talk) 17:41, 2 December 2014 (UTC)
replies: text: Are you asking for better coverage of the math in this article, or better references for the details of the mathematics? The second reference in the article is Liddle's cosmology book, which is quite good. That said, it might be good to have a few more textbooks as "Further Readings". - Parejkoj (talk) 19:05, 2 December 2014 (UTC)
replies: text:  Which maths in the article are you talking about? I see only one equation:  p = - \rho c^{2} . Otherwise there is only verbal description and a list of numerical values of parameters. Shouldn't the parameters be associated with their defining equations? A list of parameters is not a model. The book of Liddle is readable but unreliable. For instance he discusses the expansion of the universe by Newtonian dynamics and attributes it to Friedmann whereas this approach is due to Milne (and McCrea). Also he uses classical Maxwell-Boltzmann statistics for the Big Bang - not even using special relativity! JFB80 (talk) 18:32, 3 December 2014 (UTC)
replies: text:  Including some more mathematics in the article is a good idea: why don't you try to add some? However, full derivations of many of the topics of this article require far more length than is appropriate here, so we're better off with good references. As to Liddle's approaches to the topic, they are a great way to explore the behavior of different cosmologies at the advanced undergraduate level; no SR or GR is needed for a lot of this stuff. I suppose we could cite Peebles Principles of Physical Cosmology, though it's not specifically LCDM. - Parejkoj (talk) 20:26, 3 December 2014 (UTC)
replies: text: Not being a professional cosmologist I was interested to see included the actual relativistic equations used by the professionals, i.e. their model with parameters included. Lengthy full derivations would not be necessary as is normal Wikipedia practice. As regards Liddle I now understand from your comment why he uses these simplifications but even so he should quote the correct origins for the methods used. JFB80 (talk) 20:54, 4 December 2014 (UTC)
thread_title:  Where's the maths? 

message: The meaning of "reionization" is obscure.  I think a description of the physics of the physical event would be very helpful in this article.BuzzBloom (talk) 15:34, 9 April 2015 (UTC)
thread_title: Meaning of "reionization"

message: lamða as ðe, ðat, ðough (ð: a specific form of th)  — Preceding unsigned comment added by 2A02:587:410B:9E00:1C6D:429C:2CFE:BD2E (talk) 11:22, 13 May 2017 (UTC)
thread_title: Alternative spelling

message: I have read the book "Gravity" by Hartle and "Precision Cosmology" by Jones and also looked into the paper "Planck 2015 results" but I never read that the age of the universe is considered an independent parameter. In fact, it is calculated from the densities. So how do you get to this statement made in the table, which is retrieved from the Planck paper? Ulrich Utiger (talk) 13:08, 15 March 2018 (UTC)
replies: text: There are several possible choices for the "third" independent parameter in LambdaCDM. In the recent literature (e.g. Planck), the third parameter is usually something called  \theta_*  which is a "sound horizon angle" derived from the CMB measurements. This angle is somewhat technical, but it is actually highly correlated with the age of the universe (for given values of the first two parameters) so for the level of this Wikipedia article it is probably more useful to stick with the age. TychosElk (talk) 20:28, 19 April 2018 (UTC)
thread_title: Age of the universe an independent parameter?

message: There are no citations given for many of the parameters in the table in the Parameters section. The values for many cosmological parameters such as 0 and 8 are under debate, with different ways of calculating the value giving significantly different results. Slauhale (talk) 23:09, 10 October 2018 (UTC)
replies: text: The table is titled "Planck Collaboration Cosmological parameters" and there's a citation in the title to the Planck results. - Parejkoj (talk) 16:58, 11 October 2018 (UTC)
thread_title:  Citations for calculated parameter values 

message: Why is "Lambda" capitalised in this term? We don't capitalise uses of Greek letters in terms such as in "alpha particle" or "gamma ray". Nurg (talk) 01:01, 13 October 2019 (UTC)
replies: text: Because the standard symbol in astronomy literature is upper-case Greek Lambda.  Unlike alpha particle or gamma ray which use the lowercase letters. TychosElk (talk) 19:55, 13 October 2019 (UTC)
thread_title:  Capitalisation of "Lambda" 

message: In August a paper was published in Nature outlining the discovery of the remaining missing Baryonic matter, https://doi.org/10.1038/s41586-020-2300-2, however this wikipedia article has not yet been updated to reflect this discovery. I'm not an expert in Astrophysics/Cosmology so any help to fix up the missing baryonic section to reflect this discovery would be much appreciated. 
GreenJonan (talk) 11:01, 27 October 2020 (UTC)
thread_title:  Missing Baryon's - found 

message: Mission science: 
ESA's Planck mission mapped the CMB to unprecedented levels of precision between 2009 and 2013. Simulations of the Universe, based on lambda-CDM gave such a good fit to the observations that when Planck's first all-sky map was released in March 2013, the cosmologists involved called it an almost perfect Universe. The conclusion was that the Universe is made of 4.9 percent ordinary matter, 26.8 percent dark matter and 68.3 percent dark energy.
The success makes it essential that we now answer the questions: what is dark matter and dark energy? Although there are many hypotheses, scientists have not been able to detect dark matter in laboratory experiments or come up with a convincing explanation for the nature of dark energy. Both point to unknown physics at work in the Universe. In particular, dark matter cannot be explained by the Standard Model of particle physics, and dark energy cannot be reconciled with quantum theory. This is where the Euclid mission comes in.
... Following Euclid, NASA will launch the Nancy Grace Roman Space Telescope. (Last Update of the quoted text: 25 June 2020) 
We might mention in the lemma that results of EUCLID will probably help to improve the CDM model . I am no native  speaker and do not want not edit in this article. LDV-GS (talk) 07:58, 3 July 2023 (UTC)
thread_title:  [[Euclid (spacecraft)]] is on its way to L 2