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I Implications of validating loop quantum cosmology

  1. Aug 30, 2017 #26
    Urs
    ever thought about writing a resesarch paper to this effect?

    if a research group were to successfully strict deformation quantizations of gravity expressed as Ashketar variables,
    1- what would be some qualitative features you would expect to see in a strict deformation quantizations of gravity expressed as Ashketar variables
    2- would you take it as a serious candidate theory of planck scale physics
    3- would certain issues such as resolving the semiclassical limit be easier to arrive at?
    4- how would strict deformation quantizations qualitative features be similar or different from the current polymer quantization?

    would you prefer LQC to also be done as a strict deformation quantizations?
     
  2. Aug 31, 2017 #27

    Urs Schreiber

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    Sure, when it's done I am going to claim the million dollar prize money ;-)

    Regarding your other questions: Beware, as I said, that it is not clear that strict deformation quantization of gravity will exist as an "non-perturbative effective field theory", but it would be very interesting to investigate the existence in its correct and precise form, something which has received almost no attention yet. If it exists, it should be independent of which variables are used to describe the phase space, though it might have more convenient expressions in one choice of variables or the other.

    You seem to be asking whether quantum gravity could be a serious candidate theory of planck scale physics. This sounds like a tautology to me, or else I am misunderstanding what you are after here.

    That's built into the very definition of "strict deformation quantization": This is a continuous deformation, parameterized by the value of Planck's constant, which interpolates continuously between the classical theory and the non-perturbative quantum theory at some finite value of Planck's constant (if it exists, that is).

    The concept of strict deformation quantization is a mathematically precise formalization of ordinary/standard/established/observed quantum theory. It's standard established physics, just phrased in precise enough terms to guarantee that everything makes sense and we don't trick ourselves into thinking we have found a quantization while in reality we didn't. That "polymer quantization" instead is an example of the latter error.

    What is called LQC is nothing but the proposal that the differential equation that describes FRW-like cosmological models is to be replaced by a finite difference equation. That this is the quantization of anything is a conjecture without any evidence.

    While we are waiting for non-perturbative quantization theory to develop, the next thing that should be done in quantum cosmology is probably clean discussion of perturbation theory of quantum fields (gravity plus other fields) on a classical curved background, as in BFHPR 16 . For instance I am being told that presently there is still a gap in the derivation of the nature of Hawking radiation of gravitons themselves.
     
  3. Aug 31, 2017 #28
    In context, i was asking if a "strict deformation quantization" of Ashketar variables could be a serious candidate theory of planck scale physics, since the discussion was that you regard polymer quantization to be unrelated to known physics, and that if Ashketar variables could be successfully quantized using "strict deformation quantization" instead of polymer quantization, what would be its qualitative features.

    would there still be spin networks, area and volume operators in "strict deformation quantization" of Ashketar variables?
     
  4. Aug 31, 2017 #29

    Urs Schreiber

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    Regarding the area operators in LQG polymer quantization: Their specific nature is directly connected to the polymer-style prescription, with a disconnected copy of SU(2) associated wiith each edge of a spin network, each being quantized separately.

    If you are looking for solid results that support the wide-spread intuition that quantum gravity will reveal that the nature of spacetime itself becomes fuzzy/quantized on small scales, I recommend
    which works out in technical detail how string field theory retains causal locality macroscopically albeit this being manifestly broken on the string scale.
     
    Last edited: Aug 31, 2017
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