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Simple question about spontaneous particle production

  1. Oct 21, 2009 #1
    okay, so pairs of particles can be created spontaneously out of nothing (from ZPE?), and then within the time allowed by HUP, recombine and annihilate each other. correct so far? if they do not recombine, they each become real particles, (does that mean we have stolen energy from nowhere?).

    the particles must, by definition, comprise a particle and its antiparticle. generally, when a particle and antiparticle annihilate, energy (pairs of high-energy photons) is released. so, first question:

    1. is energy actually released into the universe when particles produced by spontaneous particle process recombine and annihilate? or does the (virtual?) energy released from the annihilation get "absorbed" back into the ZPE from which it came? if no energy is released, how does the universe know the difference between "real" particle/anitparticle annihilation and the annihilation of spontaneously created particles (are they not real particles)?

    hawking radiation apparently depends on the capture of a "negative energy" particle by a BH. i thought real particles such as electrons and positrons both had positive energy, just opposite charge and mirror image. frankly, i do not understand how a particle can have negative energy. so, second question:

    2. does one of the particles created during spontaneous pair production have a negative energy state? how? what is the difference between them and regular particles/antiparticles that would give them negative energy?
  2. jcsd
  3. Oct 21, 2009 #2
    No particle has negative energy, but I don't know exactly where the additional energy comes from if they do not recombine, perhaps it is taken from the system that does not allow them to recombine? For example, loss of gravitational field energy of a black hole as it leaks due to Hawking radiation? That's a speculation and I don't know for sure.

    I believe a lot of the explanation to this question is due to 'vacuum energy', which I don't understand massively myself.
  4. Oct 21, 2009 #3
    No, it is not correct. It is overly popularized picture. The physical vacuum is the lowest energetic state. Take an atom in its ground state. There is no virtual particles. Only if one looks at the atomic wave function as at "fluctuations" of electric charge, one invents such stuff as "spontaneous springing up" or something alike. Its just a vulgarization of science.

    If you put an atom in an electric field, it can get ionized. You see, the electron is not created from nothing. The same is valid for pairs.
    Last edited: Oct 21, 2009
  5. Oct 21, 2009 #4
    mikey - inre: "No particle has negative energy." from the wiki entry on hawking radiation, it states: " In order to preserve total energy, the particle that falls into the black hole must have a negative energy" - now i know that wiki isnt flawless, but i have read pretty much the same comment in a variety of references. what do you think they are talking about?

    bob - your response completely confused me. are you saying that there is no such thing as spontaneous particle pair production?

    thanks to you both for responding.
  6. Oct 21, 2009 #5
    No, there is a spontaneous particle production, like atom ionization in electric field (kind of tunneling effect). The pair arise not from nothing but from the ground pair states.

    You know, the positronium is a neutral system but with mass. There is even lower pair ground state - with zero energy. Like two charges put "very close" to each other, speaking classically. To excite such a state or separate charges one needs a strong electric field.
  7. Oct 21, 2009 #6
    I don't know, that's not the way I was taught it. The next part is something like "from an observer who is distant", so my question is, who cares what they think about a particle which spent its entire life in a causally disconnected part of spacetime to them? I guess that's not too helpful though.

    Wikipedia I find is awful at getting to the point, and always rambles around a subject without delivering the crucial concise explanation that a textbook can deliver, so I'm interested to read about this negative energy viewpoint as expressed by other people. I have seen a positron been described as negative energy in a similar way that a "hole" in a conductor full of electrons is, that is, hole+electron = annihilation.
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