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What Are We Missing in Our Search for Quantum Gravity?

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Foundations of Mathematics and Physics One Century After Hilbert

Abstract

Some reflections are presented on the state of the search for a quantum theory of gravity. I discuss diverse regimes of possible quantum gravitational phenomenon, some well explored, some novel.

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Notes

  1. 1.

    The idea that there might be quanta of gravitational waves was first mentioned by Einstein in a paper in 1917 [1].

  2. 2.

    Hence, this is a companion paper to [2].

  3. 3.

    But see [4].

  4. 4.

    Note that this is the contribution to the action from a corner of a causal diamond, and hence comes into an action directly, without being integrated over time.

  5. 5.

    See [21] for discussion of how the first law of thermodynamics plays a role in these arguments.

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Acknowledgements

I am grateful to Joseph Kouneiher for including me in this volume. I would like to thank Andrzej Banburski, Linqing Chen, Bianca Dittrich, Laurent Freidel, Henriques Gomes, Jerzy Kowalski-Glikman, Joao Magueijo and Yigit Yargic for very helpful discussions and encouragement.

I am also indebted to Stacy McGaugh, Mordehai Milgrom and Maurice van Putten for very helpful correspondence.

This research was supported in part by Perimeter Institute for Theoretical Physics. Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Research and Innovation. This research was also partly supported by grants from NSERC and FQXi. I am especially thankful to the John Templeton Foundation for their generous support of this project.

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    Lee Smolin

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Smolin, L. (2018). What Are We Missing in Our Search for Quantum Gravity?. In: Kouneiher, J. (eds) Foundations of Mathematics and Physics One Century After Hilbert. Springer, Cham. https://doi.org/10.1007/978-3-319-64813-2_11

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