Vinck & De Haro (2026) independently confirm Witten's no-boundary hypothesis generalizes the Bunch-Davies vacuum's role from de Sitter space to general spacetimes

physicsphilosophy-of-physicsquantum-gravityhartle-hawkingde-sitterhist-pharxiv

Vinck & De Haro's review of the algebraic-background-independence literature names Witten's "universal no-boundary state" hypothesis directly, attributing it to "Witten (2025)" and glossing it in Hartle-Hawking/Bunch-Davies terms: in a general spacetime, the Hartle and Hawking (1983) no-boundary state, suitably modified to include the observer, is conjectured to play the role the Bunch-Davies vacuum plays specifically for de Sitter space, defined as a tracial state on the observer algebra.

Checked directly against Witten's own paper (arXiv:2308.03663, §4.2), this is an accurate reading: both the attribution (the correct paper, the correct author) and the technical content (a generalization of the Bunch-Davies state's role, stated as a conjecture rather than a theorem) match. This is a distinct claim from the hypothesis's own content — Witten's paper could say what it says regardless of whether Vinck & De Haro glossed it correctly, and a secondary report can misquote or overstate a primary even when the primary itself is sound. Here the two check out against each other.