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Quantum gravity and cosmology

  1. Oct 2, 2013 #1
    Most people here I think will agree that in order to understand what happened at the big bang we most likely need a quantum theory of gravity.
    There do appear to be models of cosmology such as CCC or Baum/Frampton that seem to try and sidestep this requirement, but looking at quantum gravity seems to be the mainstream approach.
    I would like to keep this post open to have a directory for what different approaches to quantum gravity imply about what happened at the big bang. The main approaches I have listed below with articles that are as easy to understand as I can find regarding what they predict happened 13.8 bio years ago

    String/M theory:
    Pre big bang model of Veneziano

    Bounce model also from Veneziano

    Ekpyrotic model of Steinhardt and Turok

    Big bounce

    But according to the Wikipedia page there are may other approaches to quantum gravity other than the main two (string theory and LQG). Can anyone fill in the blanks as it were with what they predict and any useful articles? I have made a start with Horava Liftshitz gravity. But more are welcome.

    Acoustic metric and other analog models of gravity

    Asymptotic safety in quantum gravity

    Causal Dynamical Triangulation[41]

    Causal sets[42]

    Group field theory[43]

    Hořava–Lifshitz gravity
    Matter bounce

    MacDowell–Mansouri action

    Noncommutative geometry.

    Path-integral based models of quantum cosmology[44]

    Regge calculus

    String-nets giving rise to gapless helicity ±2 excitations with no other gapless excitations[45]

    Superfluid vacuum theory a.k.a. theory of BEC vacuum


    Twistor models[46]

    Canonical quantum gravity

    E8 Theory

  2. jcsd
  3. Oct 3, 2013 #2
  4. Oct 4, 2013 #3
    Hi thanks for that , I dont have this book, if you have any comments on what the canonical QG implies for the big bang, would love to hear it.
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