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I had always thought that our physical universe had this property as well, i.e. the Everett multiverse branches into the past as well as into the future.
If you take a single branch and run it backward, you'll find that it diverges into a multiverse of its own. If you take all the branches and run them backward, their branches will cohere instead of decohering, cancel out in most places, and miraculously produce only the larger, more coherent blobs of amplitude they started from. Sort of like watching an egg unscramble itself.
And the beings in them will only have memories of further-cohered (further "pastward") events, just as if you didn't run anything backwards.
And at the beginning of the universe we have a set of states which just point time-backwards at each other, which is why we cannot go meaningfully more backwards in time.
Something like:
A1 goes with probability 1% to B1, 1% to C1, and 98% to A2.
B1 goes with probability 1% to A1, 1% to C1, and 98% to B2.
C1 goes with probability 1% to A1, 1% to B1, and 98% to C2.
So if you ask about the past of A2, you get A1, which is the part that makes intuitive sense for us. But trying to go deeper in the past just gives us that the past of A1 is B1 or C1, and the past of B1 is A1 or C1, etc. Except that the change does not clearly happen in one moment (A2 has a rather well-defined past, A1 does not), but more gradually.
As I understand it, this is not how standard physics models the beginning of time.
I don't think anyone takes seriously the way standard physics models the beginning of time (temperature and density of the universe approaching infinity as its age approaches zero), anyway, as it's most likely incorrect due to quantum gravity effects.
This is a correct usage of terminology but the irony still made me smile.
What?
I think wedrifid is pointing to the irony in saying that the 'standard' model is (on some issue) standardly rejected.
Oh. I tried to find something, but the only thing that partially pattern-matches it was the Hartle–Hawking state. If we mix it with the "universe as a Markov chain over particle configurations" model, it could lead to something like this. Or could not.