Hartle-Hawking no-boundary state

A proposal in quantum cosmology, originated by James B. Hartle and Stephen W. Hawking in their 1983 paper "Wave function of the Universe" (Physical Review D 28(12):2960): the universe's quantum state is defined by a path integral over compact Euclidean four-geometries with no initial boundary, replacing the question "what were the initial conditions?" with "there was no initial moment to have conditions." It is distinct from the Bunch-Davies vacuum, the specific quantum state built for de Sitter space by matching short-distance behavior to flat-space quantum field theory — the no-boundary state is a proposal about the whole universe's wave function, while Bunch-Davies is a vacuum choice for quantum fields on one fixed background.

The vault met this state through Vinck & De Haro's 2026 review of Edward Witten's algebraic quantum-gravity program, which reports that Witten (2023/2025) conjectures the no-boundary state, suitably modified to include an observer, generalizes the role the Bunch-Davies vacuum plays specifically in de Sitter space to any spacetime. Witten's own paper states this as an explicitly labeled, two-part, self-admittedly speculative hypothesis, checked rigorously only for de Sitter vacua of varying cosmological constant. A direct read of both documents confirms Vinck & De Haro's gloss accurately represents Witten's own claim.

References

• claim-witten-2023-universal-no-boundary-state-hypothesis
• claim-vinck-de-haro-2026-confirm-witten-no-boundary-bunch-davies-generalization
• claim-vinck-de-haro-2026-no-existing-definition-captures-wittens-background-independence-claim
• claim-witten-ferreiro-cavallaro-semiclassical-gravity-strands-no-cross-citation
• Capture: 10-inbox/raw/2026-10-16-outside-arxiv261022042-on-algebraic-background-independence-physicshist-ph.md
• Capture: 10-inbox/raw/2026-10-20-wittens-2025-conjecture-that-a-suitably-modified-hartle.md

Log

• 2026-10-20: Page created on promotion of the 2026-10-20 Witten capture — the vault's second contact with this concept (first met 2026-10-16, via Vinck & De Haro's secondhand gloss, but not yet given a page). James Hartle and Stephen Hawking, who originated the state in 1983, remain mentions rather than hub entities in this vault: both are named only as co-authors of the single 1983 paper this literature keeps citing, and neither yet has independent standing here beyond that one joint work.