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Hawking Radiation and Entanglement

  1. Dec 5, 2014 #1
    I am at odds over how Hawking Radiation can cause a problem with entanglement - or even how the pair particle to a Hawkings particle can enter a black hole.

    The notion behind Hawking Radiation, as I understand it, is that a particle divides above the event horizon creating two entangled particles. One escapes, the other crosses the event horizon into the black hole.

    But given "Bob's" frame of reference, the one from well outside the event horizon, nothing crosses the event horizon. Alice (the adventuress who dives into the hole) may see a black hole's interior, but it is simply not part of Bob's universe. And that Hawkings radiation that Bob sees isn't part of Alice's universe. Nobody see's a paradox.

    So why are some worried about Hawkings particles becoming entangled with each other?
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  3. Dec 5, 2014 #2


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    I'm not aware that entanglement is an issue w/ Hawking radiation but that could just be my own ignorance.

    More importantly, this whole business of "particle pairs" being what Hawking radiation IS, is a a red herring. Hawking himself said that this was an ANALOGY that was the best he could do to give an English language description of what the radiation REALLY is, which can only actually be described with math. I don't have a citation for that but when I mentioned it in a post some months back, someone gave a citation for it in that thread.
  4. Dec 5, 2014 #3


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    The Hawking information paradox doesn't have anything to do with the particle-anti-particle pair entanglement. It simply has to do with the fact that the Hawking radiation is thought to be completely thermal in nature, and not carrying any information content what-so-ever. Therefore, all the information in all the states of particles which fell into the black hole to make it will eventually be lost.
  5. Dec 5, 2014 #4
    One aspect of the issue of entanglement bears (or apparently bears) on the issue of the firewall.

    When Bob watches Alice fall through the event horizon, I believe most people now agree that he sees her fried by a firewall. On the other hand, Alice should not see any indication of the firewall - because event horizons are purely a product of your reference frame. If the Hawkings radiation is created by virtual (and therefore entangled) pairs, it explains how Alice would see nothing. If these pairs are not virtual, then they can't be hidden from Alice - so Alice will see the firewall - violating the "No Drama" arguments about event horizons.

    My point is simply that it doesn't matter if the pairs are entangled because from Bob's point a view, the descending particle never makes it to the event horizon anyway.
  6. Dec 5, 2014 #5
    So you are comfortable with quantum information being destroyed or created? From what I gather, most people who work with QM are not. In fact, in a video just posted to another thread by Doug Huffman, Professor Leonard Susskind listed it as the "-1st" law other thermodynamics - two positions in the list before the first law of thermodynamics.
  7. Dec 5, 2014 #6
    That's not all there is to it. The black hole information paradox as usually stated is that even if you just assume the information that fell into the black hole gets encoded into the Hawking radiation somehow in order to preserve unitarity, then the information seems to exist in two places at once. Hawking radiation emanates from the event horizon of a black hole, not its interior, and so just prior to emission the information appears to exist both at the black hole's boundary and in its interior. This would violate the No Cloning Theorem and hence unitarity. That's why it's called the black hole information paradox rather than, say, the black hole information problem: it seems like you have to allow unitarity to be violated in order to prevent unitarity being violated.

    Why do you think Matterwave is comfortable with information being destroyed? He was explaining what the black hole information paradox is, not dismissing it as a non-problem.
  8. Dec 5, 2014 #7
    Ahhh. You're right. After rereading, he was only describing the paradox.
  9. Dec 5, 2014 #8


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    Bob does not see Alice disappearance and Alice still receive Bob's photons.
  10. Dec 5, 2014 #9
    The debate is whether Alice sees the firewall. I see no reason why Alice should see the firewall. That's important because Bob's event horizon isn't suppose to be significant to Alice - it's just more space that she's falling through.

    Alice will see things very different from Bob. But what is important is that nothing that Alice sees violates any of the QM rules. In other words, you can't put together a paradox based on a combination of what Alice sees and what Bob sees. They are allowed to see very different things.
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