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Cosmological Perturbations from the No Boundary Euclidean Path Integral

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arxiv astro-ph/9902265 v1 pith:7G5THTLX submitted 1999-02-18 astro-ph gr-qchep-ph

Steven Gratton , Neil Turok This is my paper · ORCID
classification astro-phgr-qchep-ph
keywords euclideanfluctuationsintegralpathboundarycosmologicalinstantonsperturbations
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We compute, from first principles, the quantum fluctuations about instanton saddle points of the Euclidean path integral for Einstein gravity coupled to a scalar field. The Euclidean two-point correlator is analytically continued into the Lorentzian region where it describes the quantum mechanical vacuum fluctuations in the state described by no boundary proposal initial conditions. We concentrate on the density perturbations in open inflationary universes produced from cosmological instantons, describing the differences between non-singular Coleman-De Luccia and singular Hawking-Turok instantons. We show how the Euclidean path integral uniquely specifies the fluctuations in both cases.

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Cited by 3 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Superconformal indices and black hole saddles

    hep-th 2026-08 conditional novelty 7.0 of 10

    At large Im tau the superconformal index tends to 1, and the authors show that a Picard-Lefschetz analysis of a Lorentzian-inspired bulk integral enforces this by making all exponentially large black hole saddles irre...

  2. How to tame your (black hole) saddles: Lessons from the Lorentzian Gravitational Path Integral

    hep-th 2026-03 accept novelty 6.0 of 10

    A Lorentzian path integral contour for charged AdS black holes selects a finite subset of complex saddles via Picard-Lefschetz theory, ensuring the semiclassical sum converges at finite β.

  3. Euclidean wormholes stability analysis revisited

    hep-th 2025-05 conditional novelty 6.0 of 10

    Even-parity perturbations of Euclidean axion wormholes have finite, positive quadratic actions when the constraint equations are solved differently, so prior exclusions of these modes were artifacts and the known stab...

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