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Spacetime scaling invariance and quantum gravity

  1. Oct 8, 2015 #1
    Neil Turok, Director of the Perimeter Institute of Theoretical Physics in Ontario, Canada suggests scaling invariance is a fundamental property of nature, including spacetime. that nature does not recognize any kind of scale, including planck scale.

    if true how would this affect the leading theories of QG like string theory LQG etc. are there any theories of gravity and quantum gravity that respect scaling invariance? how would gravitons be affected if nature is scaling invariant?

    Turok seems to think scale symmetry is a fundamental symmetry.

    since scale is important in the real world, what breaks this symmetry?

    what does this mean for the other symmetry supersymmetry?
    he also thinks the higgs might also exhibit scaling invariance http://www.perimeterinstitute.ca/people/Neil-Turok
     
  2. jcsd
  3. Oct 10, 2015 #2
    Shape Dynamics is a locally scale invariant gravity theory. Koslowski et al showed that scale invariance in SD is deeply linked with the time refoliation invariance in GR. While they are still formulating SD as a quantum theory there is some evidence that it has a scale anomaly ie the invariance is broken at a quantum level.
    See "Scale Anomaly as the Origin of Time."
    Barbour, Lostaglio, Mercati arXiv:1301.6173v1
     
  4. Oct 10, 2015 #3
    thanks i'll look it up.
    does string/m theory lqg supergravity et al, respect scale invariance?
     
  5. Oct 11, 2015 #4
    LQG is not scale invariant as usually formulated because it has minimum area and volume operators. There was a suggestion from Kosloswki that LQG may be made scale invariant by reformulating it using unlabelled graphs but I don't know if that has gone anywhere.

    I don't know enough about the others to comment.
     
  6. Oct 11, 2015 #5

    haushofer

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    String theory is conformal on the worldsheet, and I guess it is also conformal in spacetime whenever you're dealing with only the massless modes.

    Conformal invariance in supergravity is used as a trick to describe matter couplings via so called superconformal tensor calculus. But the theory itself exhibits just superpoincare invariance, because the gauge fields belonging to the dilation and special conformal transfo's can be solved for or gauged away.
     
  7. Oct 13, 2015 #6

    ohwilleke

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    This seems a very odd foundation for a fundamental physical theory given the myriad circumstance of physics where phenomena manifest themselves at some scales and not others. Atoms and stars and black holes and galaxies, for example, all have very distinctive scales, the very fundamental constants of the universe run with energy scale in the SM, and the CMB data is inconsistent with scaling invariance.
     
  8. Oct 14, 2015 #7
    http://www.perimeterinstitute.ca/people/Neil-Turok
    4) I am fascinated by the results of detailed measurements of the universe on large scales. The presence of dark energy, as well as the extreme simplicity in the large scale structure, seem to me profound clues which no existing theoretical paradigm adequately explains. They may be pointing towards new physical principles, such as conformal symmetry and its spontaneous breakdown, and I am interested in exploring frameworks within which this may be studied.

    he obviously thinks it is broken
     
  9. Oct 15, 2015 #8
     
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