Editing Hartle–Hawking state (section)

{{Short description|Proposal concerning the state of the universe prior to the Planck epoch}}
[[File:Big Bang Singularity and Hartle-Hawking State.jpg|thumb|400x400px|''[[Big Bang]]'' and Hartle–Hawking State diagram.]]
The '''Hartle–Hawking state''', also known as the '''no-boundary wave function''' is a proposal in [[theoretical physics]] concerning the state of the [[universe]] prior to the [[Planck epoch]].<ref>{{Cite journal | volume = 28 | pages = 2960 | year = 1983 | doi = 10.1103/PhysRevD.28.2960 | last1 = Hartle | journal = Physical Review D | first1 = J. | title = Wave function of the Universe | last2 = Hawking | first2 = S. | issue = 12|bibcode = 1983PhRvD..28.2960H | s2cid = 121947045 }}</ref><ref>{{Cite journal |last=Lehners |first=Jean-Luc |date=June 2023 |title=Review of the no-boundary wave function |url=https://linkinghub.elsevier.com/retrieve/pii/S0370157323001904 |journal=Physics Reports |language=en |volume=1022 |pages=1–82 |doi=10.1016/j.physrep.2023.06.002|arxiv=2303.08802 }}</ref><ref>{{Cite journal |last=Weinberg |first=Steven |date=1989-01-01 |title=The cosmological constant problem |url=https://link.aps.org/doi/10.1103/RevModPhys.61.1 |journal=Reviews of Modern Physics |language=en |volume=61 |issue=1 |pages=1–23 |doi=10.1103/RevModPhys.61.1 |hdl=2152/61094 |issn=0034-6861|hdl-access=free }}</ref> It is named after [[James Hartle]] and [[Stephen Hawking]].