NetNews Usenet Archive 1993 #1/NN_1993_1.iso/spool/sci/physics/22129

Internet Message Format | 1993-01-05 | 3.5 KB

Path: sparky!uunet!gatech!destroyer!news.itd.umich.edu!pablo.physics.lsa.umich.edu!metzler
From: [e-mail] (Chris Metzler)
Newsgroups: sci.physics
Subject: Re: Request info on Cold Dark Matter
Date: 5 Jan 1993 22:48:56 GMT
Organization: University of Michigan Department of Physics
Lines: 51
Distribution: world
Message-ID: <[e-mail]>
References: <[e-mail]> <[e-mail]>
NNTP-Posting-Host: pablo.physics.lsa.umich.edu
Keywords: cold dark matter, cosmology

In article <[e-mail]>, [e-mail] (Mike Gross) writes:
|> In <[e-mail]> [e-mail] (Tomi Erik Salminen) writes:
|>
|> >I am doing an undergraduate project on cold dark matter (i.e. WIMPS,
|> >axions, quark nuggets, black holes, monopoles, cosmic strings... any
|> >more?). If anyone on the net knows any good references on any of these
|> >and would be kind enough to email me about them, I'd sure appreciate it.
|>
|> >Is hot dark matter (neutrinos) the best bet today?
|>
|> You might try Kolb & Turner, "The Early Universe," chapters 9 and 10, and the
|> references in that book. This gives a nice intro to minimal CDM. WARNING: COBE
|> results have shown that minimal CDM is not correct, since it creates too much
|> structure at small scales if one normalizes the distribution to the large
|> (COBE) scales. This came out *after* the book was published. However, you need
|> to understand it in order to see the significance of non-minimal CDM.

1.  This is to Tomi Erik Salminen.  I don't know what your background is, but
you might also try Blumenthal, Faber, Primack, and Rees, "Formation of Galaxies
and Large-Scale Structure with Cold Dark Matter," Nature v. 311, 11 Oct 1984;
Davis, Efstathiou, Frenk, and White, "The Evolution of Large-Scale Structure
in a Universe Dominated by Cold Dark Matter," Ap.J. v292, 15 May 1985.  These
are indeed two of the references cited in Kolb and Turner, but maybe you'd
like to get your feet wet right away.  I'm surprised Mike didn't tell you
about the first article right off, since he's Joel Primack's grad student.

2.  Hi Mike.  Hope things have gone well since Varenna.  I would take a
small amount of exception with your statement that "COBE results have
shown that minimal CDM is not correct, since it creates too much structure
at small scales if one normalizes the distribution to the large (COBE)
scales."  I would take exception to this.  Remember that the simulations
people have done which have told them that there's too much structure on
small scales assume that the collisionless particles in the N-body
simulations are accurate tracers of galaxies.  I am NOT talking about
spatial bias (biased CDM) here.  Galaxy formation simulations which include
both N-body and hydro suggest that there exists velocity bias even in
unbiased CDM models, whether from dynamical friction or from the
nature of the environment galaxies are born into.  Thus, the whole
"pairwise-velocity-dispersions are too high" problem may not even exist.
You may be right, but I think the jury is still out; the impression
I'm starting to get from the CDM gurus is 'hey, maybe unbiased CDM
wasn't so bad after all.'

--
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Chris Metzler                                    313-764-4607 (office)
Department of Physics, University of Michigan    313-996-9249 (home)
Randall Lab, 500 E. University
Ann Arbor, MI  48109-1120 USA

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