Hadron collider CERN

[harry]

G'day from the land of ozzzz

There are many theories on dark matter. The matter that is hidden or cannot be seen and I'm not talking about planets an objects that we see as normal matter.

Here is one theory

A theory of dark matter
Jan-09
http://adsabs.harvard.edu/abs/2009PhRvD..79a5014A

We propose a comprehensive theory of dark matter that explains the recent proliferation of unexpected observations in high-energy astrophysics. Cosmic ray spectra from ATIC and PAMELA require a WIMP (weakly interacting massive particle). with mass Mχ˜500 800GeV that annihilates into leptons at a level well above that expected from a thermal relic. Signals from WMAP and EGRET reinforce this interpretation. Limits on &pmacr; and π0-γ’s constrain the hadronic channels allowed for dark matter. Taken together, we argue these facts imply the presence of a new force in the dark sector, with a Compton wavelength mϕ-1≳1GeV-1. The long range allows a Sommerfeld enhancement to boost the annihilation cross section as required, without altering the weak-scale annihilation cross section during dark matter freeze-out in the early universe. If the dark matter annihilates into the new force carrier ϕ, its low mass can make hadronic modes kinematically inaccessible, forcing decays dominantly into leptons. If the force carrier is a non-Abelian gauge boson, the dark matter is part of a multiplet of states, and splittings between these states are naturally generated with size αmϕ˜MeV, leading to the eXciting dark matter (XDM) scenario previously proposed to explain the positron annihilation in the galactic center observed by the INTEGRAL satellite; the light boson invoked by XDM to mediate a large inelastic scattering cross section is identified with the ϕ here. Somewhat smaller splittings would also be expected, providing a natural source for the parameters of the inelastic dark matter (iDM) explanation for the DAMA annual modulation signal. Since the Sommerfeld enhancement is most significant at low velocities, early dark matter halos at redshift ˜10 potentially produce observable effects on the ionization history of the universe. Because of the enhanced cross section, detection of substructure is more probable than with a conventional WIMP. Moreover, the low velocity dispersion of dwarf galaxies and Milky Way subhalos can increase the substructure annihilation signal by an additional order of magnitude or more

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[Chris Peterson]

To this date no dark matter or energy has been observed as noted by the BBT.

Dark matter is regularly observed. Dark energy is hypothesized as a mechanism for other observations, but may not be directly observable in any usual sense of the word.

Most matter is found at the centre of Stars, and other compact objects such as exotic stars and black holes (without a singularity)

Most matter is dark matter, and isn't in stars. As for the ordinary matter in stars, very little of it is compressed into an exotic regime.

[canuck100]

this is just my personal take but for me, even the term 'matter' conjures up solid objects when in fact what we perceive as matter is mostly empty space. (Well ... except for dark energy ... dark matter ... oh and the occasional pair of virtual particles spontaneously arising from the vacuum energy !!! ) So I prefer to think of everything as energy density rather than matter. My feeble imagination finds it easier to accept that energy can be compacted nearly infinitely.
Otherwise, how does one define 'matter' so as to discuss its density?

I'm sure there are numerous sources quoting % of various types of energy. Google turned up a 2005 paper at http://www.wired.com/science/space/news/2005/02/66487 for me:

Whereas baryons account for 4 percent of the total matter and energy in the universe, dark matter is thought to make up 23 percent. The remaining 73 percent of the so-called matter-energy budget consists of what scientists call "dark energy."

So most of the matter in the universe is dark matter/dark energy which, according to most mathematical models, permeates all space and is therefore anything but compact.

[canuck100]

http://www.cfht.hawaii.edu/News/Lensing/CFHT Gives First Glimpse of Dark Matter Distribution

This distribution of dark matter doesn't look particularly compact either.

[canuck100]

I was very curious about the claim that most matter is in the form of compact matter as it seems on the face of it a possibility. Because of how dense compact matter is, it could conceivably comprise a fair chunk of the total mass of the universe.

How much so called compact matter is the universe estimated to contain? Let's use the Milky Way as a starting point. I performed a few simple calculations just to see and here is what I get -- please correct me if I'm wrong.

How about using the estimated total mass of all neutron stars and the central black hole of the Milky Way as a starting point estimate of the total amount of compact matter. The cores of other stars contain elements from hydrogen up to iron so they do not contain so called compact matter and are therefore excluded.

Scenario #1
Estimated total mass of milky way http://en.wikipedia.org/wiki/Milky_Way 3 trillion sons or approx. 10^^12 solar masses

Estimated mass of central black hole http://en.wikipedia.org/wiki/Sagittarius_A 3.7 million solar masses or 10^^6 solar masses
This is 10^^-8% of the total mass. Pretty small.

Estimated number of neutron stars in milky way http://www.brighthub.com/science/space/ ... /8937.aspx 10^^9 (of which a mere 2000 are observed BTW)
Estimated mass of average neutron star http://en.wikipedia.org/wiki/Neutron_star between 1.35 and about 2.1 solar masses
Total mass of neutron stars in the Milky Way is therefore on the order of 10^^9 solar masses or one tenth of one percent of the total mass. Pretty small.

Scenario#2
Well, you say, that 3 trillion suns contains the dark matter and I meant to include only 'normal' matter. OK, do the same calculations using only 4% of the 3 trillion suns as a total mass -- an order of magnitude of 10^^10 solar masses.
This still results in the central black hole being 10^^- 6% of the total mass and the neutron stars being 10% of the total mass.

[harry]

G'day from the land of ozzzzzzz

My advice is keep reading.

Not just the links that I post, in actual fact go on a self discovery.

In the mean time

http://arxiv.org/abs/astro-ph/0403206
Cores of Dark Matter Halos Correlate with Disk Scale Lengths

Authors: F. Donato (University and INFN, Torino), G. Gentile, P. Salucci (SISSA, Trieste)
(Submitted on 9 Mar 2004 (v1), last revised 13 Jul 2004 (this version, v3))

Abstract: We investigate in detail the mass distribution obtained by means of high resolution rotation curves of 25 galaxies of different morphological types. The dark matter contribution to the circular rotation velocity is well-described by resorting to a dark component whose density shows an inner core, i.e. a central constant density region. We find a very strong correlation between the core radius size $R_C$ and the stellar exponential scale length $R_D$: $R_C \simeq 13 (\frac {R_D} {5 {\rm kpc}})^{1.05} {\rm kpc} $, and between $R_C$ and the galaxy dynamical mass at this distance, $M_{dyn}(R_C)$. These relationships would not be expected if the core radii were the product of an incorrect decomposition procedure, or the biased result of wrong or misunderstood observational data. The very strong correlation between the dark and luminous scale lengths found here seems to hold also for different Hubble types and opens new scenarios for the nature of the dark matter in galaxies.

[Chris Peterson]

My advice is keep reading.

Reading isn't very useful if you don't accompany it with thinking!

Consider the analysis of canuck100, who read some basic facts about stellar types, thought about the significance of the different types, and performed a useful calculation. If you disagree with his conclusion, you should identify a problem with his reasoning.

[canuck100]

While very interesting, this thread has wandered very far from the original topic Hadron collider CERN so in the interests of rational organization, I suggest that a moderator lock this thread.
A new thread can always be started to explore some of the very interesting topics that have been begun in this one.
cheers
jk

[harry]

G'day from the land of ozzzzz

These links have just being emailed to me.

The person saw my comment and in a flash posted these links.

http://arxiv.org/abs/0909.2900
Resonant Dark Matter

http://arxiv.org/abs/0909.3145
Slow Galaxy Growth within Rapidly Growing Dark Matter Halos

http://arxiv.org/abs/0909.3527
The Distribution of Dark Matter Over 3 Decades in Radius in the Lensing Cluster Abell 611

http://arxiv.org/abs/0909.3936
Mass Distribution in Hickson Compact Groups of Galaxies

Since I have not read these, I will come back to you.

Before I do that, time to take the kids out and smell the roses.

[bystander]

Per request this topic is being closed. It has diverged considerably from the original topic. I caution all posters to stay on topic. When posting outside references, state the relevance to the topic at hand. If you can not relate the article to the topic, do not post the reference. This forum is not the place to post reading lists just for the sake of posting. If it's not relevant, don't post.