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Gravitational Double Slit

  1. Jun 23, 2003 #1

    drag

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    Greetings !

    I see that my original thread called "Uncertain Gravity?"
    did not get the attention that I hoped it would (a level
    at least sufficient to answer the question I'm now separately
    posting here).

    So, the question:
    What does modern physics say about the double slit experiment
    where a gravitational wave detector is placed near a slit
    instead of an EM wave detector (or a nuclear detector since
    the weak and strong forces have been included in later theories
    that deal with them based on the quantum approach) ?
    (And if you don't know that, then - what do you think ?)

    Thanks ! :smile:

    Live long and prosper.
     
  2. jcsd
  3. Jun 23, 2003 #2
    Don't know what 'current science' says, but if I recall it properly a gravitational wave detector is being built in the US, it is called LIGO for Large Interferometry Gravitational Observatory, and if I recall again correctly, it is rather huge, (Mile{s} long) not something that you could place in a lab behind the double slit experiment, if that is the one you talking about.

    Otherwise, sorry to take up your time. My 2 ¢


    EDIT SP!! x 2
     
    Last edited: Jun 24, 2003
  4. Jun 23, 2003 #3

    FZ+

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    I don't quite understand this. How do you diffract gravity waves if as far as we know there is no way to shield from gravity or change it's rate of propagation?
     
  5. Jun 23, 2003 #4

    jeff

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    Since gravity couples to everything, it seems unlikely that a consistent TOE could be constructed that allows gravity to escape governance by the quantum rules that govern everything else. For this reason, such theories haven't been pursued. In fact, the converse issue of what the implications of quantization are for GR, and in particular, for the principle of equivalence and diffeomorphism invariance is a common worry.

    The problem of diffeomorphism invariance doesn't lend itself well to you're question, but I have seen the issue of the equivalence principle dealt with in terms of, for example, particles diffracted by a "gravitational grating". However the results of such gedanken experiments don't throw the equivalence principle into doubt.
     
    Last edited: Jun 23, 2003
  6. Jun 23, 2003 #5

    LURCH

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    Well, that is the sticky in the wicket, no? Perhaps the two slits could be in a berrier of Bose-Einstein Condensate (if these are shown to "block" gravity, which I find hard to accept).
     
  7. Jun 24, 2003 #6

    drag

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    Greetings !

    jeff, thanks for your response. :smile:
    Could you, please, tell us a bit more about what
    "diffeomorphism invariance" is and how exactly the
    equivalence principle is related here (for the poor
    hobbyists amongst us, like me ).
    But you can alter the course and shape of the wave, right ?

    So, suppose you have a nutron going through a slit and you send
    a gravity wave. The nutron itself also bends space-time so
    the wave should be somehow affected by it in the above manner
    (I guess ).

    The question is, will this "detection" collapse the WF ?
    If not, what will it detect ? And will this mean that
    we can get around the HUP through GR and find out what
    that QM "mess" is all about ?

    Live long and prosper.
     
  8. Jun 24, 2003 #7
    in a low gravity limit it is possible to construct a quantum field theory of gravitons - whether this is valid or not remains to be tested - so if a single graviton was diffracted through some version of the double slit experiment, it would act "exactly like a photon" in a similar experiment.

    As stated above, it might be possible to set up refractive barriers that allow slit like experiments to b e conducted.

    Joe
     
  9. Jun 24, 2003 #8

    drag

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    Greetings !
    What do you mean by "low gravity limmit" ?
    And why is that ?
    Actualy, I'm just asking about the theory of what will happen.
    Like I said before - I don't think that such an experiment will
    be practicly possible any time soon (and that's probably
    an understatement :wink:). But, if someone got an idea on
    how to do it - go right ahead and tell us ! :smile:

    Live long and prosper.
     
  10. Jun 24, 2003 #9

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    [Oopsey.... What was I thinking?]
     
    Last edited: Jun 25, 2003
  11. Jun 24, 2003 #10

    drag

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    I'm not certain what precisely is the problem here.
    This is not a novel idea at all.

    Live long and prosper.
     
  12. Jun 25, 2003 #11
    my recollection of the details is fuzzy - but:
    at low enough gravity you can neglect nonlinearities, and then vibrations in space time obey equations analogous to light - which are then amenable to quantization as per the standard methods of QM -> gravitons.

    It is possible that a gravitational version of an einstein ring (big GW source behind massive object could yeild some sort of interfenernec epattern in GW's - not positive how you could measure the pattern with ligo though

    Joe
     
  13. Jun 28, 2003 #12

    drag

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    Any other opinions on this ? :smile:
     
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