Talk:Structure formation

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"hot, dense, nearly uniform state approximately 11 billion years ago"? I thought the consensus figure was more like 13 or 14 billion. --arkuat (talk) 19:48, 19 May 2006 (UTC)

Merge suggestion[edit]

Interestingly enough, these two articles developed organically and there is very little overlap. Please, someone help us merge! --ScienceApologist 06:59, 17 June 2006 (UTC)

I have removed the merge tag. I agree that the two articles are closely related, but I envison large-scale structure of the universe as being a sort of broad, non-technical overview, while this article could be more technical and include more detailed referencing. This is a project I've been lazily putting off for a long time. As you can see, I've made a start, but plenty more can be added. One interesting thing would be to include a hand-waving explanation of why the CMB anisotropy spectrum looks the way it does, à la Wayne Hu. I also intend to add something about how to go from cosmic inflation -> linear structure -> N-body with some mathematical details (although not a complete description). –Joke 01:45, 22 September 2006 (UTC)

Millenium Simulation[edit]

While I agree that the Millenium simulation of Springel and colleagues is very important, being the largest of its kind ever done, it should be placed in the proper context of the previous thirty years of N-body simulations. Rtfisher 13:47, 19 June 2006 (UTC)

Comments[edit]

I've recently been trying to expand the page. I think I've put in a pretty good framework for what should eventually go here, but the following needs to be improved:

  • It's too technical in places
  • It is completely unreferenced. I intend to address this soon, but I wrote it without bothering too much about references so that I could at least get something sensible up.
  • It needs illustrations, here are some ideas:
    • The CMB anisotropy spectrum
    • An illustration of the Hubble radius compared to the expansion of space during inflation
    • The large-scale structure power spectrum (preferably with SDSS or 2dF/GRS data)
    • A 2d slice of one of the big N-body simulations showing filaments

I also intend to write something about the mathematical formalism behind this all, but I haven't decided whether to add it to cosmological perturbation theory and N-body simulation or to this page. Comments welcome. –Joke 13:08, 25 September 2006 (UTC)

Dark matter — discrepancies[edit]

Which of the interactions (forces)?[edit]

This same article has a contradiction about the forces in one and the same section. First it cites that «It may be composed of particles that interact through the weak interaction, such as neutrinos...» (the weak interaction is also "allowed" in another article, Dark matter[1]); in the very next paragraph it suddenly occurs that «…it feels only the force of gravity: the gravitational Jeans instability which allows compact structures to form is not opposed by any force...»... What's the point and where's the accepted one? Josh, linguist (talk) 19:06, 19 September 2013 (UTC)

"Baryonic/non-baryonic" — ?[edit]

Well, in this article, that same section tells us that it is a dichotomy with dark and baryonic matter:

Dark matter interacts through the force of gravity, but it is not composed of baryons and...

; and also twice indirectly:

Recent evidence suggests that there is about five times as much dark matter as baryonic matter...

and

At this stage, luminous, baryonic matter is expected to simply mirror the evolution of the dark matter...

. While the Dark matter article has a whole section — the second there — named Baryonic and nonbaryonic dark matter, which begins with

There are three separate lines of evidence that the majority of dark matter is not made of baryons, ordinary matter...

, which, applying some logic, means that baryonic/dark in not a dichotomy.

So what do we do? Josh, linguist (talk) 19:53, 19 September 2013 (UTC)


References[edit]

  1. ^ «The most widely accepted explanation for these phenomena is that dark matter exists and that it is most probably composed of weakly interacting massive particles (WIMPs) that interact only through gravity and the weak force.»