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Distunguishing matter/antimatter black holes

  1. May 14, 2010 #1
    You have two black holes of the same mass and charge widely separated in space. One was formed from matter and one from antimatter. Are there any experiments which could be conducted outside the horizons which would distinguish the two?


    PS Sorry if this is the wrong forum. Couldn't decide if relativity, astrophysics, particle physics would be the right place. Feel free to move it.
  2. jcsd
  3. May 14, 2010 #2


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    My understanding is no, you can't tell. Matter and anti-matter both have positive mass. Once the event horizon has formed and the black hole has stabilized, it's external characteristics are completely determined by it's mass, charge, and angular momentum, and all information about the nature of the matter that fell into it is lost.
  4. May 14, 2010 #3
    I will answer your question with a circumstantial argument:

    If you find a black hole in the center of a matter galaxy, you can safely assume that matter contributed to the mass.
    On the other hand, if you find an antimatter galaxy, it will likely have a black hole at the center which got its mass primarily from in-falling antimatter.

    By the way, if you do find an antimatter galaxy, please let me know!!
  5. May 15, 2010 #4
    I have a question -
    can matter or anti-matter exist in a black hole?
    I am under the impression that the heat and density inside a black hole would preclude the existance of matter - even charged particles wouldn't exist, would they?
  6. May 15, 2010 #5
    Objects that fall past the event horizon of a black hole still "exist".
    Though, we can't do any experiment outside the event horizon to measure their properties other than charge, spin, and mass.
    Also, the information contained in the in-falling object does still exist, even though it is hidden from view.
    It is debatable how and even if this information re-enters the universe at large after a black hole evaporates!

    The heat and density at the event horizon depends on the mass of the black hole.
    A galactic black hole will have a huge radius.
    Ignoring the accretion disk, you won't even notice when you pass the event horizon.
    You'd just continue to fall inward towards the singularity until tidal forces rip your atoms apart.
    For a galactic black hole, this could take a long time!
    Just what happens at the singularity is unknown, so if you told me that matter doesn't exist there, I'd have a hard time arguing with you.
  7. May 16, 2010 #6
    So, if a matter BH and an antimatter BH were to collide it is unknown if the result would be a larger BH or an incredible explosion?

  8. May 16, 2010 #7
    A larger BH according to current theory, because as mentioned by phyzguy, black holes have no hair and there's no such distinction as matter or anti-matter black holes.
  9. May 16, 2010 #8
    petergreat is correct.
    Say I construct 2 black holes in my lab, one from collapsed antimatter, one from collapsed matter.
    When I bring these two objects together, they merge into a black hole who mass is the sum of the two.
    No explosion.

    Inside the event horizon, the matter and antimatter may be coming into contact, but since the light cones all point in towards the singularity, none of the radiation from the resulting annihilation will ever escape!
  10. May 16, 2010 #9
    Should it be true, the lepton and barion numbers would be violated (or worse).

    Suppose you create two black holes, one from neutrons and one from antineutrons. Then you let them both evaporate via Hawking mechanism. What particles will these holes split into? We must assume that a hole remembers all conserved quantum numbers. Forgetting too much would imply violation of some conservation laws.

    Also, current theory (GR alone) states that a black hole does have some hair. The "no hair" property is only about idealized symmetric stationary hole that have existed from infinity and will exist forever. Any other hole will have some information encoded in its event horizon's shape.
    Suppose you have a hole of some mass and you have 2 bodies of masses m1 and m2. You throw the 2 bodies into the hole, one after another. Now: can you extract information from the hole, which body you have thrown first? Yes, you can!

    The shape of event horizon depends on all particles that you have thrown into the hole and also on the particles that you will throw in the future. The last words simply state that the exact shape of the horizon in unmeasurable, because the very act of measurement will change it. This looks for me suspiciously like QM uncertainty.

    I have read all of this from Penrose, I suppose.
  11. May 17, 2010 #10
    The baryon number is http://en.wikipedia.org/wiki/Baryon_number" [Broken] according to Wikipedia.

    In fact, current theory says black holes are a great way of breaking baryon number symmetry. It is thought that in quantum gravity, the formation of virtual black holes is a possible channel for proton decay.
    Last edited by a moderator: May 4, 2017
  12. May 18, 2010 #11
    Whatever. Black hole must remember any conserved charge. Do you say that only mass and electric charge is conserved?
    Last edited by a moderator: May 4, 2017
  13. May 18, 2010 #12

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    Why do you say that? The no-hair theorem would suggest that this is not necessarily true.
  14. May 18, 2010 #13
    Why you ask? It's kinda axiom for me. Anything (including BH) must remember any conserved charge, or else this charge would not be conserved.
    Does no-hair theorem even consider other charges than mass, electricity and angular momentum?

    On the other hand, you can reject Hawking radiation. The hole would not have to remember anything then.
  15. May 18, 2010 #14


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    Bhs appear to be extremely efficient scramblers of quantum states, so its highly unlikely that standard model accidental symmetries, custodial symmetries and other such approximate symmetries have any hope of being a good description for quantum physics around such an object. So things like baryon and lepton number are most likely violated (I say most likely, b/c the resolution of the information loss paradox isn't entirely settled). Now a better question, perhaps is what about B-L, a symmetry that seems exact in the standard model.

    A lot depends on what type of beyond the standard model physics you wish to postulate and the bottomline is that no one really knows.
  16. May 19, 2010 #15
    How the Black Hole is created in our Universe ?
    It happens when 2 massive stars collide. It is not a simple collision - you have remember there is a time dilation when the Mass/Radius is near c^2/2G. Therefore for us the distant observers the Black Hole will never formed.
    All superheavy stars we observe are Black Hole Like Objects or Eternally Collapsed Objects (ECO). Time dilation is confirmed but not the classic Black Hole.

    Now. Every star is rotating and it creates a magnetic moment. We have a good theory that the particle-antiparticle are created in such a strong gravitational field and the magnetic field seperates them. Particles go up and antiparticles go down - therefore we observe jets consists of matter mainly (electrons, protons, neutrons). There is a little antimatter.
    This antimatter falling down annihilate with the matter of the BHLO (ECO) and we observe gamma rays.
    The matter from an accretion disc falls down , creates matter-antimatte from the dense vacuum and is ejected in the jets. Antimatter is collected down in the star and may overcome the matter inside the ECO.
    I assume all the Black Hole Like Objects are build of antimatter.
  17. May 23, 2010 #16
    well i don't think that there would be any big characteristic difference, because matter an antimatter are both of the same fundamentals. So if they have the same mass, i think that they will have the same gravitational force. Can somebody teach me more.
  18. May 23, 2010 #17


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    What is B-L?
  19. May 23, 2010 #18
    I don't mean to hi-jack the thread, but would ordinary matter be distinguishable from anit-matter?

    For example - say we were looking at a galaxy a few billion light years away, composed of the same basic elements only in their anti-matter form. Would there be any way to know it was different?
  20. May 23, 2010 #19
    Baryon number minus lepton number.

    A basic question: do you believe that gravity and electromagnetism can somehow describe ALL physics? Is there no need for any other interaction?
    If you would say no, black holes will remember some conserved charge associated to the new interaction.
    I don't know if it is B-L or something. Maybe we already know this charge (say weak hypercharge), or maybe there is something more fundamental.

    However, black holes definitely will have to remember something more than electric charge and mass. Unless gravity+EM is everything we have in our universe.
    Maybe this additional "something" would distinguish between matter and antimatter.
  21. May 24, 2010 #20
    the antimatter has reverse polarity inside the atom, so could we detect it?
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