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I Are there any linear quantum gravity theories?

  1. Jan 4, 2017 #1
    Are there any linear quantum gravity theories out there with respect to the wave function?
     
  2. jcsd
  3. Jan 4, 2017 #2

    dextercioby

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    You can quantize the (Pauli-Fierz) free spin-2 field (which is the 1st order perturbation of the space-time metric) canonically or better yet with path integrals as normal linear QFT (just like electromagnetism in Minkowski spacetime). There's a (probably the best) chapter of Zee's book on QFT on this. The Pauli-Fierz action is deducted by Feynman in his GR book from symmetry considerations.
     
  4. Jan 5, 2017 #3

    Demystifier

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    All mainstream quantum gravity theories (string theory, Wheeler-DeWitt, loop quantum gravity, perturbative quantization of spin-2 field in a classical background, etc.) are linear with respect to the wave function. Linearity (or superposition principle) is one of the basics axioms of quantum theory.
     
  5. Jan 5, 2017 #4

    haushofer

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    Maybe you're confusing fields with wave functions ?
     
  6. Jan 5, 2017 #5

    Demystifier

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    Who are you referring to? The OP stated that he is talking about linearity with respect to wave functions. I assumed that by "wave functions" he means quantum states and not the gravitational fields. Dextercioby assumed the opposite.
     
  7. Jan 6, 2017 #6

    haushofer

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    I meant the OP. If so, the question seems to make more sense to me.
     
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