On 2/2/2014 3:35 PM, LizR wrote:
On 3 February 2014 08:03, meekerdb <[email protected] <mailto:[email protected]>>
wrote:
On 2/2/2014 1:44 AM, LizR wrote:
Someone asked how a block universe "comes to exist" and if it comes into
existence
"all at once, or a bit at a time" (or something like that).
I wish I could find the original question, to make sure exactly what it
was. But I
haven't managed to find it, and I can't spend all night trawling the forum
for it,
so I will just put my take on the matter here.
Assuming I've got it right, this seems to me a rather odd question. Asking
how a
block universe comes into existence presupposes that this is a process that
must
happen within a time stream.
I can imagine a semi-block universe in which, as you've often remarked, the
past is
a block and the universe keeps adding new moments and growing. This would
be like
Barbour's time capsules, except just sticking everything into one capsule,
like a
history book that keeps adding pages. But yes it implies another exterior
"time" in
which this "happens"; but then so does Bruno's UD.
I don't think Bruno would agree with that. I think the UD is supposed to function simply
by existing, and each state is defined relative to another one....somehow. (But at this
point my brain melts...)
My point is that we needn't take these models seriously. We just use them
to try to
picture things.
Right.... maybe.... not sure what you mean. That is, I'm not sure where the line is
between which models one should take seriously (if any) and which ones are "just for
picturing". Did Minkowski take space-time seriously? Does it matter? I thought the
important things were prediction of (preferably unexpected) consequences, and being open
to refutation.
I assume as we get more into interpretation and general meta-ness, refutation comes to
rely more on logical inconsistency or similar meta-refutations. But things can
occasionally be "de-meta-ised" as our knowledge improves. This happened for block
universes with SR. The experimental evidence for space-time being a 4D manifold is the
relativity of simultaneity. I assume that before this, the concept was "just an
interpretation" - it was the only picture that made sense of Newtonian physics, but
(apart from thought experiments like "Laplace's godlike being") it was not considered
experimentally testable. You just had to accept it on logical grounds (or posit extra
time streams). Then along came Einstein, and showed that it /was/ experimentally
testable after all.
I guess it's possible the MWI will undergo a similar "demetaisation" at some point,
perhaps if quantum computers factoring very large numbers become commonplace...
That's sort of what is attempted here:
Born in an Infinite Universe: a Cosmological Interpretation of Quantum
Mechanics
Anthony Aguirre <http://arxiv.org/find/quant-ph/1/au:+Aguirre_A/0/1/0/all/0/1>,Max Tegmark
<http://arxiv.org/find/quant-ph/1/au:+Tegmark_M/0/1/0/all/0/1>
(Submitted on 5 Aug 2010 (v1 <http://arxiv.org/abs/1008.1066v1>), last revised 12 Jun 2012
(this version, v2))
We study the quantum measurement problem in the context of an infinite,
statistically
uniform space, as could be generated by eternal inflation. It has recently
been argued
that when identical copies of a quantum measurement system exist, the
standard
projection operators and Born rule method for calculating probabilities must
be
supplemented by estimates of relative frequencies of observers. We argue
that an
infinite space actually renders the Born rule redundant, by physically
realizing all
outcomes of a quantum measurement in different regions, with relative
frequencies
given by the square of the wave function amplitudes. Our formal argument
hinges on
properties of what we term the quantum confusion operator, which projects
onto the
Hilbert subspace where the Born rule fails, and we comment on its relation
to the
oft-discussed quantum frequency operator. This analysis unifies the
classical and
quantum levels of parallel universes that have been discussed in the
literature, and
has implications for several issues in quantum measurement theory. It also
shows how,
even for a single measurement, probabilities may be interpreted as relative
frequencies in unitary (Everettian) quantum mechanics. We also argue that
after
discarding a zero-norm part of the wavefunction, the remainder consists of a
superposition of indistinguishable terms, so that arguably "collapse" of the
wavefunction is irrelevant, and the "many worlds" of Everett's
interpretation are
unified into one. Finally, the analysis suggests a "cosmological
interpretation" of
quantum theory in which the wave function describes the actual spatial
collection of
identical quantum systems, and quantum uncertainty is attributable to the
observer's
inability to self-locate in this collection.
http://arxiv.org/pdf/1008.1066v2.pdf
Everett's multiple worlds are reified even more than just being projections of the
universal state, they are assigned to classically distinct universes.
Brent
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