Does Dark Anti-Matter exist?

  1. I imagine it must....Could we have dark anti-matter in our universe that doesn't interact with ordinary matter?
    Would this example say Baryon asymmetry?
  2. jcsd
  3. cristo

    cristo 8,386
    Staff Emeritus
    Science Advisor

    Dark matter doesn't interact by the electromagnetic force, thus is not charged. Hence there is no such thing as dark anti matter.
  4. dark matte is a form of ordinary matter as u said ,,,,just interact gravitational forces
  5. Wow,I forget the basic definition, thinking of something more complex....

    We don't know what dark matter is made of right?
  6. mgb_phys

    mgb_phys 8,809
    Science Advisor
    Homework Helper

    There are anti neutrinos and anti neutrons.
    Do you mean that if dark matter is non-baryonic you can't have anti dark-matter?
    Presumably only particles with spin can have anti particles?

    There are two main theories, cold dark matter is ordinary stuff ( gas, dust, rocks) that is too cold and dark to see but still has a gravitational effect, because we can model the formation rate of material from the bigbang quite well it doesn;t look like there could be enough of this.
    Hot dark matter (or non-baryonic) is unknown particles that don't have electromagnetic effects so don't give off light. This looks more likely, but there is always a danger of coming up with a solution that involves being able to 'make up' whatever properties you like for your solution.
  7. Astrophyiscs measured gravitational effect of dark matter
    surround the galaxies right? as the gravitational lenses
  8. mgb_phys

    mgb_phys 8,809
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    Homework Helper

    I don't know if you would call a gravitational lens an electromagnetic effect.
    Perhaps I phrased it badly - dark matter doesn't generate light and doesn't seem to effect the properties of light passing through/near it, so we cannot see it directly - hence dark.
    Last edited: Aug 19, 2008
  9. So what's an antineutron? Antihydrogen? And like someone else said, antinetrino? OK, so the first two have internal components which are charged, but having charge is not the requirement for having an antiparticle, antimatter has all quantum numbers reversed, including charge if applicable.

    If dark matter is made of supersymmetric particles, then I'm pretty sure those have antiparticles just like normal matter does. A quick search for "anti-neutralino" (my favourite DM candiate) on Google throws up several scientific papers, so I didn't sleep through my supersymmetry lectures and dream it! Of course, it might not be supersymmetric particle, but we can't say for sure whether the type of particle dark matter is made of has an antiparticle until we know what it is!

    As for matter/antimatter asymmetry, I presume it must either be all dark matter or all anti-dark-matter or it would have annihilated by now. I presume any asyemmetry would be through pretty much the same mechanism as the matter/anitmatter asymmetry in normal matter, so I would be very suprised if the DM was all antimatter.
  10. what i meant it that the dark matter has a gravitational effect on light...
    not electromagnetic effect...(by stimulating electrons if electrons exist in dark matter)
    just like when a light beam passes near to a star or
    his path will be curved for a what can we say about a galaxy?
    am i right?
  11. if there's antimatter, there should be anti dark matter
  12. Antimatter is exactly the same as matter except it has the opposite electrical charge. Since Dark Matter seems to have no interaction with electrical charge, it cannot have an opposite electrical charge. The answer would seem to be, no.
  13. Uncharged particles can have antiparticles.
  14. This is all speculation. No one knows what dark matter is. Until we find it, there isn't even any direct proof that it exists as we have only "seen it" from the effects which most attribute to it (rather than some modified gravity theory).

    Since know one knows what it is, (or even, some small groups might argue, if it exists), no one can tell you if there are dark-matter anti-particles as we don't really know how to begin to argue what that might mean.


    We know what dark matter does and what it cannot be but we don't know what it is.
  15. There's an argument called the "WIMP miracle" that can explain the amount of dark matter present in the universe today if dark matter particles and their antiparticles were produced in equal numbers and have been annihilating ever since, provided the particles have a weak-scale mass and cross section. So it's plausible that there's equal amounts of dark matter and antimatter. But the argument also works if the dark matter particle is its own antiparticle, which is a strong possibility given that these particles can't be charged. It's all speculation, though, until we find out what dark matter really is.
  16. Absolutely yes.....

    In fact, people have used the possibility that dark anti-matter/matter exists to put limits on what it might be. Start at page 73 on this paper

    The idea is that if dark matter was particle X, some of it must be particle anti-X, and therefore we should see gamma rays or positrons from X and anti-X annihilating each other. If we go out looking for these gamma rays or positions, and we see them, they we figure out what it is. If we don't see them (which we don't), we can figure out what dark matter isn't.
  17. My rough guide is that stuff you see in the night sky all lit up is about 4% of the mass of the universe, and it's all baryonic.
    Other baryonic stuff you can't see is cold , like black holes, dark stars, lone planets , asteroids, shrapnel, and gas. About 8%.
    Then there's hot dark matter - mostly neutrinos. Some mass but probably a small percentage.
    Unknown dark matter about 12%.
    dark energy about 70%.
  18. My thoughts are that there is Matter/Antimatter and yes, Dark Matter/Dark Antimatter. My thought on that is that Dark matter has its own set of quarks and bosons. So there would be Dark Leptons, Dark Mesons, Dark Baryons, Dark Bimesons, Dark Barymesons, Dark Trimesons and Dark Dibaryons. Matter/Antimatter DIRECTLY interacts with Matter/Antimatter. Dark Matter/Dark Antimatter DIRECTLY interacts with Dark Matter/Dark Antimatter. My own (strongly disputable) theory on annihilation is that when a particle interacts with its antiparticle, the annihilation yields a decay series of particles of the opposing kind. e.g. a Proton interacts with an Antiproton, the Matter yield is nothing, but Dark Matter yield occurs (not a Dark Proton and Dark Antiproton, but can't rule out the possiblity).
  19. Why? Do you have any science to back up that statement?
  20. It does seem that when a dark matter particle meets its anti-particle, both would be annihilated.
  21. PAllen

    PAllen 5,890
    Science Advisor
    Gold Member

    One of the more popular proposals for dark matter is the lightest (therefore stable) neutralino of supersymmetric models. In such models, the neutralino is its own antiparticle.
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