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Is a tabletop search for Planck scale signals feasible

  1. Nov 19, 2012 #1


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    This paper - http://arxiv.org/abs/1211.3816 - by Beckenstein is fascinating. I would like to know if the experimental test proposal is realistic.
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  3. Nov 19, 2012 #2


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    Cool! He seems to discuss thermal vibration transmitted through atoms of gas, photons, and thermal contact through the fiber. However, he doesn't seem to discuss non-thermal sources of vibration. Hasn't he simply designed the world's most sensitive seismometer? These vibrations aren't thermal in nature, and can't be eliminated by cooling. I don't understand the last section of paragraph II, which seems to be addressing something related to this. The first two sentences don't seem to be connected logically to the rest of the paragraph.

    This seems very similar to what LIGO does, but they're still measuring displacements many, many orders of magnitude above the Planck scale. I guess the big difference is that Bekenstein's design involves time intervals that are short (e.g., compared to the time between hits by atoms of gas), whereas LIGO uses time intervals that are long, so they're in the business of averaging out the thermal fluctuations.

    In his discussion of vacuum, he says that He is what you'd choose to use, because the low mass is more favorable. But when you're trying to achieve high vacuum, you don't necessarily get to choose what gas it is you're pumping out. Different types of vacuum pumps work differently (e.g., cryopumps get rid of stuff that condenses, turbopumps work on everything). I've never worked with high vacuum at this level, and I don't know what techniques they use. But I suspect that you might be dealing with a lot of high-molecular-mass gunk such as finger grease or stuff that outgasses from various surfaces, which also might be high in molecular mass.
    Last edited: Nov 19, 2012
  4. Nov 19, 2012 #3


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    I would expect mainly hydrogen in the vacuum, as it can diffuse through other materials easily. It is the dominant contribution in the LHC vacuum, for example.

    If the accelerations are slow, it might not matter.

    I think the general assumption there that photon transmission depends on the displacement is very speculative, even if that displacement is of the order of the planck length.
  5. Nov 25, 2012 #4
  6. Nov 25, 2012 #5


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    Bee Hossenfelder comments on the paper here:

    Bee is a recognized expert in quantum gravity phenomenology and has organized 3 international conferences on the experimental search for QG effects. She is familiar with the main QG models and can judge whether the proposed experiment actually would test any of them.

    There was also a blog entry at the MIT Technology Review website. It doesn't say who the author was and it doesn't sound as if the author knows anything about actual QG theories---the blog post impresses me as being somewhat on the vague, naive side.

    EDIT: I see sanman has already given a pointer to the TechReview blog post. The short answer would be to read Bee's post.
    Last edited: Nov 25, 2012
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