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If Dark Matter does self annihilate to form anti-matter, does this mean than dark matter at least partly consists of anti-matter? If this is the case then is this possibly a solution to the problem of the missing anti-matter, if that is still considered a problem of modern cosmology?
Scientists ponder missing anti-matter
Newbie
:)
i know alot for anti-mater am interested of dark mater i know only few things .. send me some information about this if ya have so ;] than i will be able to answare your queston and make the dependencez between ;] am sure it hasitz normal ... everythin is connected
Established Member
Wha? Since when have we known anything about dark matter creating darkmatter and when has there been missing antimatter?
I think your facts for the basis of this question are wrong, but then I'm not up to date on all this stuff so maybe your not...
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Well, it does look like neutralino annhiliation results in anti-matter and matter in equal abundance, so maybe not.
PAMELA: Dark Matter
Order of Kilopi
As the site notes, there are good theoretical reasons to suspect the neutralino as a dark matter particle, but this is no done deal. Neutralinos "are Majorana fermions and will annihilate with each other... resulting in the symmetric production of particles and antiparticles, the latter providing an observable signature" that PAMELA plans to capture.
Since within the first second after the big bang.Originally Posted by Durakken
As some clever wikipedist put it, "No known physics can explain the fact that there are so many more baryons in the universe than antibaryons." Apparently these must be produced in pairs, and of course matter and antimatter annihilate into radiation upon contact, so apparently, after the Grand Annihilation, which produced a lot of radiation, there was somehow a slight excess of matter particles over antimatter, and that excess now makes up all the matter in the universe.
Everyone is entitled to his own opinion, but not his own facts.
Established Member
Wasn't this already explained by some particle that changes its matter/antimatter status randomly?
Order of Kilopi
hooey
Cougar. "there was somehow a slight excess of matter over antimatter"...is an expression used by authors of "for-the general-taxpaying-public" texts of cosmology to gloss over the fact that we simply don't know why the universe exists. There is no known mechanism, hasn't been one since I was a kid (while they dropped the bombs on Hiroshima and Nagasaki), and it doesn't look like they're going to find any mechanism any time soon, either. It does help them sell books, but it is poor science, with no experimental confirmation, and remains a huge thorn in the paw of cosmological lions.As the site notes, there are good theoretical reasons to suspect the neutralino as a dark matter particle, but this is no done deal. Neutralinos "are Majorana fermions and will annihilate with each other... resulting in the symmetric production of particles and antiparticles, the latter providing an observable signature" that PAMELA plans to capture.
Since within the first second after the big bang.
Perhaps the LHC will give a clue..if not, our only hope may become sporadic cosmic ray studies.
There is also no need to postulate mass in neutrinos...as yet. see slide 86,87:http://www.docstoc.com/docs/2454655/...-MiniBooNE-Era
Established Member
Nevertheless, anti-matter is produced by separating the components in a symmetrical process, and these positrons observed by PAMELA are resulting from another; that is all known processes are symmetrical. However, the universe does not appear to contain the primordial anti-matter as evidenced from lack of positron bombardment. Now rather than correspondence to all we can see, even if dark matter provides a reservoir that may reduce this missing percentage to maybe 5-10% of mass, so either it was fractionated, or matter was produced by an (as yet unknown) asymmetric process.
Order of Kilopi
That's what I said.
What about CP symmetry violation?
Everyone is entitled to his own opinion, but not his own facts.
Newbie
Hooey is close on the money I think!
Dark matter (and the other dark forces?) are concepts that have been created to compensate for the inaccuracies in our currently limited mathematical modelling of the Universe.
Recent experiments suggest that there may well be a variation in the nature/strength/manifestation of magnetic forces across the Universe. If one force varies from "place to place" then probably they all do - or is that a dangerous assumption?
Order of Kilopi
what makes you think dark matter self annihilates?
Established Member
"Neutralino are Majorana fermions and will annihilate with each other in the halo, resulting in the symmetric production of particles and antiparticles, the latter providing an observable signature. With Pamela we look for annihilations that produce antiprotons and positrons."
PAMELA
Established Member
Just because something can decay or annihilate to produce antimatter doesn't mean it contains antimatter any more than Uranium contains Xenon. If these annihilations did happen they would be symmetric, that is to say that quantum numbers would be conserved and so equal amounts of matter and antimatter would be made (as your quote says). Unless they broke CP - and so far we just don't know enough about these hypothetical neutralinos (NB: their existence is dependent on supersymmetry which is also unproven). So I guess what you could say is that IF supersymmetry is right and IF dark matter is mainly neutralinos and IF they decay via a CP violating weak interaction then they could produce an excess of antimatter. But that in no way explains the missing antimatter problem unless there is some production mechanism for neutralinos that used up antimatter preferentially to matter. So many ifs and so untestable that it is hardly worth speculating on the subject to be honest.
Order of Kilopi
There should be no "assumptions", dangerous or otherwise. I'm not sure what you mean by variation of magnetic forces across the universe and it is not clear why this would have anything to do with gravity or dark matter.
What makes one hypothesis (e.g. dark matter) "hooey" and another (I assume you mean something like changing gravitational force, e.g. MOND or similar) not? I would say that it is the level of evidence. At the moment the evidence is piling up in favor of dark matter. With a few interesting open questions...
Established Member
There's this sense that antimatter is "dangerous" because for many particles they only have to get near some matter and they attract each other and explode in a burst of energy. But not all antimatter is "dangerous" like that. If you have a neutral particle with low cross-section in its interaction with other matter, then its antiparticle is probably equally innocuous. Neutrinos are a kind of dark matter that we have known about for a long time. Antineutrinos are formed during beta decay, at least, so are reasonably common around here. Antineutrinos are probably passing straight through all of us barely ever interacting as I write. So we already know that some dark matter is in the form of antimatter.
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