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Status of Hawking Hartle no boundary proposal

  1. Apr 12, 2012 #1
    I came across this statement from James Hartle on Stephen Hawking's website,


    and wondered where you see this proposal currrently [Hartle sure seems to think it explains an awful lot] :

    James Hartle:

    Wikipedia has a brief discussion here:
    Hartle–Hawking state

    which explains that
    If there are updates in ARXIV I'd be interested in a few you experts consider worthwhile....I could not find anything, but that's likely a reflection of my lack of search skills...

    Are there any 'competing theories' where time emerges before space....or other entities come first, say, gravity.....??
  2. jcsd
  3. Apr 14, 2012 #2
    So nobody's come with a different view than space emerges before time??

    If so, not such a good commentary on the last 25 years of quantum theory.
  4. Apr 16, 2012 #3
    I'm struggling to remember, but doesn't the HH proposal result in an expanding universe with closed spatial 3-slices? That's problematic given that cosmological measurements suggest that our universe is spatially open (just!). If I recall correctly there's no obvious way to modify the mechanism to produce the open case.

    Note: this is really a beyond standard model topic - you might get some more informed opinions if you post it there.
  5. May 1, 2012 #4
    Here's an excerpt from an article by Sean Carroll which seems to directly conflict with the much older theory of Hawking Hartle:

    and then explains the Hawking Hartle view:
    " The other possibility is that the universe doesn’t evolve at all — the Hamiltonian is zero, and there is some space of possible states, but we just sit there, without a fundamental “passage of time.” ....quantum cosmologists like James Hartle, Stephen Hawking, Alex Vilenkin, Andrei Linde and others have in mind when they are talking about the “creation of the universe from nothing.” In this kind of picture, there is literally a moment in the history of the universe prior to which there weren’t any other moments. There is a boundary of time (presumably at the Big Bang), prior to which there was … nothing. No stuff, not even a quantum wave function; there was no prior thing, because there is no sensible notion of “prior.”


    And so that seems to answer my question: The Hawking Hartle view is still one possibility.
    Last edited: May 1, 2012
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