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Gravitationally amplified quantum fluctuations

  1. May 19, 2010 #1

    In the above article, a mechanism is suggested whereby a massive body gains mass from quantum fluctuations.

    This seems to contradict Hawking Radiation, where interaction with virtual particles result in a (very) massive body radiating away energy!

    Why would a neutron star gather mass from the vacuum energy, but a black hole shed mass via the same interaction?

    Thanks. :)
  2. jcsd
  3. May 19, 2010 #2
    The idea here seems to be that the very large energy density in the gravitational field would result in relatively large quantum fluctuations in mass density, and that perhaps these fluctuations in mass could effect some astrophysical phenomenon such as a star on the verge of supernova. The reason this is different from hawking radiation is that there is no Schwarzschild radius, so all the virtual particles are able to recombine and there is no average change in mass of the star. I am not sure how this would create energy, probably not. The virtual particles would have some potential energy due to the gravitational fields, but this would just be an instantaneous fluctuation, as their annihilation would remove the potential energy due to gravity.
  4. May 20, 2010 #3
    Thanks jrosen13, for reminding me that the Hawking Radiation occurs because one virtual pair is separated from the other!
    It makes sense that this only happens on an event horizon. :)

    I read a synopsis of the original paper here: http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.104.161102
    and I think I understand the meaning of the paper a little bit better.
    The "background metric forces the vacuum fluctuations to increase without bound" ...
    until ... " the field’s vacuum energy density will eventually dominate its classical energy density"
    So, no virtual particles are flying around free of their partners, but there is still an effect on the energy of the body.
    The uncertainty principal normally keeps quantum fluctuations down to a scale such that their effect is tiny.
    Within the neutron stars, however, there is a runaway effect where the immense mass makes the effect stronger, which makes the body more massive, etc.

    It sounds believable expect for the part where they assume "a classical background spacetime", which seems like a poor assumption in and around a NEUTRON STAR!
    Last edited: May 20, 2010
  5. May 25, 2010 #4
    coarse vs smooth fabric (Re: Gravitationally amplified quantum fluctuations)

    But doesn't the creation-anihilation of particle-antiparticle pairs mean an oscillation around the "zero-point"? Therefore any increased energy would correspond to wider oscillations around that zero-point: ie. creation of clumps of particles and antiparticles, anihilation of clumps of particles and antiparticles.

    What is the difference between sailing a calm sea and a choppy sea? Either way, you still have the same amount of water.
    A massive modern ocean-liner might not feel the difference between a calm sea and sea that's a little more choppier, but a man in a tiny liferaft would.
    If you are driving your big truck over a patch of gravel, you might not feel the difference between that and driving over a smooth road, but a tiny ant will of course see huge differences between the gravel landscape and the smoother one.

    So I don't know what effects large astrophysical objects will experience on a macro-scale, but wouldn't smallscale quantum-level phenomena experience some significant effects from this ?
    What then are all the relevant quantum phenomena occurring in the vicinity of a massive high-gravity object?

    How could one devise a means of measuring whether there is an effect on such quantum-level phenomena under such conditions? Would atomic orbitals change, for example? Would photon interference patterns change? Would quantum tunneling across a distance change?

    How can one devise a test to differentiate between "rough spacetime" and "smooth spacetime"?
    Last edited: May 25, 2010
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