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2022

Gravitational entropy and the flatness, homogeneity and isotropy puzzles

Turok, Neil, Boyle, Latham

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We suggest a new explanation for the observed large scale flatness, homogeneity and isotropy of the universe.

The basic ingredients are elementary and well-known, namely Einstein's theory of gravity and Hawking's method of computing gravitational entropy.
The new twist is provided by the boundary conditions we recently proposed for "big bang" type singularities dominated by conformal matter, enforcing $CPT$ symmetry and analyticity.
Here, we show that, besides allowing us to describe the big bang, these boundary conditions allow new gravitational instantons, enabling us to calculate the gravitational entropy of cosmologies which include radiation, dark energy and space curvature of either sign.

Gravitational entropy and the flatness, homogeneity and isotropy puzzles · Around

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G. W. Gibbons and S. W. Hawking, Eds.,“Euclidean Quantum Gravity,” World Scientific, 1993

1993

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R. P. A. C. Newman, “On the Structure of conformal singularities in classical general relativity,” Proc. Roy. Soc. Lond. A 443

1993

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R. P. A. C. Newman, “On the Structure of conformal singularities in classical general relativity. 2. Evolution equations and a conjecture of K.P. Tod,” Proc. Roy. Soc. Lond. A 443

1993

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R. M. Wald, “Quantum Field Theory in Curved Spacetime and Black Hole Thermodynamics,” Chicago Lectures in Physics (University of Chicago Press, 1994)

1994

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L. Boyle, K. Finn and N. Turok, “The Big Bang, CPT, and neutrino dark matter,” Annals of Phys., in press, [arXiv:1803.08930 [hep-ph]]

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L. Boyle and N. Turok, “Two-Sheeted Universe, Analyticity and the Arrow of Time,” [arXiv:2109.06204 [hep-th]]

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L. Boyle and N. Turok, “Cancelling the vacuum energy and Weyl anomaly in the standard model with dimension-zero scalar fields,” [arXiv:2110.06258 [hep-th]]

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2018

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J. Feldbrugge, J. L. Lehners and N. Turok, “No rescue for the no boundary proposal: Pointers to the future of quantum cosmology,” Phys. Rev. D 97

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For a recent study suggesting that the reduction in friction due to biomass burial 2 billion years ago led to mountain building, see J. Parnell and C. Brolly, Nature Communications, Earth and Environment

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M. Kontsevich and G. Segal, “Wick Rotation and the Positivity of Energy in Quantum Field Theory,” Quart. J. Math. Oxford Ser. 72

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