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B Black hole vs antimatter

  1. Mar 4, 2017 #1
    A black hole is basically extremely dense matter. What could happen if it interacted with antimatter?
    I guess a part of the black hole's mass would annihilate.
     
  2. jcsd
  3. Mar 4, 2017 #2

    Drakkith

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    Nothing observable would happen. Once the antimatter falls beyond the event horizon it is no longer possible to know what happens. The antimatter likely just falls inward towards the singularity, but we can't be sure.

    Mass cannot annihilate. Only particles can annihilate, and then their mass is converted into energy (which itself has mass). The mass of the black hole would remain unchanged.
     
  4. Mar 4, 2017 #3

    Orodruin

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    A black hole is not extremely dense matter.
    The mass would increase since the anti-matter would carry mass into the black hole.
     
  5. Mar 4, 2017 #4

    Drakkith

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    Sorry, I meant that any annihilation process that might occur would not change the mass of the black hole.
     
  6. Mar 4, 2017 #5
    Wouldn't that be assuming that a photon pair is not created as a result of the annihilation, as photons are massless?
     
  7. Mar 4, 2017 #6

    phinds

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    Photons are not massless in the way you seem to be thinking. They have no rest mass but they have an energy equivalent and so contribute to the stress energy tensor inside the EH.
     
  8. Mar 4, 2017 #7
    Ah okay I see now thanks.
     
  9. Mar 4, 2017 #8

    Orodruin

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    I would just like to point out that, for the typical Schwarzschild solution, the stress-energy tensor is identically equal to zero everywhere (i.e., the Schwarzschild solution is a vacuum solution to the EFEs). The mass of the Schwarzschild black hole is a global property of the space-time.
     
  10. Mar 5, 2017 #9
    As far as I know that energy are EM-waves, which don't have any mass.

    Btw how do you then explain the X-ray radiation coming out of the black hole if it eats something?
     
  11. Mar 5, 2017 #10

    Drakkith

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    A single photon has no mass, but a system of photons does indeed have mass. The details are a bit complicated.

    The x-rays come from the accretion disk, which is a ring of in-spiralling matter that is heated to extremely hot temperatures, emitting x-rays before it falls beyond the event horizon.
     
  12. Mar 5, 2017 #11
    Ok I see
     
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