{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"e5a85c48441a8156eacc282c32ba95de8261934a341a7f1acb45a79f77b7cd73","created":"2026-10-03T07:18:02Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["37af2c82ef6a23dc93532e942e600aae0577e8f4cfa135ee1f105d118dd8dd26","5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"42a7e9dd7f15753b6ca5235952c7f5cc89e571b09d09226c5ea02217b165cfe5","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"cosmo.quantum-cosmology.no-boundary-consistency","kind":"well-posed","literature_status":"contested","n":"1","parents":[{"note":"","parent_revision":"37af2c82ef6a23dc93532e942e600aae0577e8f4cfa135ee1f105d118dd8dd26","relation":"special_case"}],"plain":"James Hartle and Stephen Hawking, two theoretical physicists, proposed that the universe began without any boundary in time, in the way the surface of a sphere has no edge at its pole. Recent calculations disagree on whether this proposal gives a sensible universe or one with uncontrollably large ripples.","posed_since":"2017","precise":"For minisuperspace gravity with a positive cosmological constant plus linear tensor perturbations, evaluate the no-boundary amplitude as a Lorentzian path integral over the lapse using Picard-Lefschetz theory (deforming the integration contour onto steepest-descent paths). Feldbrugge, Lehners and Turok (2017, PRL 119, 171301) find unsuppressed perturbations; Diaz Dorronsoro, Halliwell, Hartle, Hertog and Janssen (2017, PRD 96, 043505) choose a contour giving a real wave function with suppressed, nearly Gaussian perturbations. Determine whether a physical principle (Wheeler-DeWitt equation with specified boundary conditions, unitarity, or a quantum-gravity completion) singles out one contour, and whether perturbations are suppressed for it.","problem_ref":null,"references":"","settled_by":"A derivation of the contour from a principle accepted by both sides, followed by the computation of the tensor perturbation amplitude on that contour.","status_note":"The 2017 dispute is unresolved; 2024 to 2026 work in Jackiw-Teitelboim gravity, spin foams and lattice Lefschetz-thimble studies has not produced consensus.","title":"Is the Lorentzian no-boundary wave function well defined and 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