---
title: "Hartle-Hawking no-boundary state"
type: "entity"
entity_kind: "concept"
status: "hub"
canonical_name: "Hartle-Hawking no-boundary state"
aliases: ["no-boundary state","no-boundary proposal","ΨHH","wave function of the universe"]
first_seen: "2026-10-16T00:00:00.000Z"
writer_model: "claude-sonnet-5"
connects_to: ["Edward Witten","Bunch-Davies vacuum (contrast)","de Sitter semiclassical gravity","algebraic quantum field theory","James Hartle and Stephen Hawking (1983)"]
seek_code_commit: "d40ee39"
---


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 [[claim-vinck-de-haro-2026-no-existing-definition-captures-wittens-background-independence-claim|Vinck & De Haro's 2026 review]] of [[entity-edward-witten|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. [[claim-witten-2023-universal-no-boundary-state-hypothesis|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. [[claim-vinck-de-haro-2026-confirm-witten-no-boundary-bunch-davies-generalization|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.