On 26 Feb 2015, at 22:01, meekerdb wrote:
On 2/26/2015 3:21 AM, Bruno Marchal wrote:
On 26 Feb 2015, at 05:36, meekerdb wrote:
On 2/25/2015 7:11 PM, Jason Resch wrote:
On Wed, Feb 25, 2015 at 5:28 AM, Bruce Kellett <[email protected]
> wrote:
Bruno Marchal wrote:
On 24 Feb 2015, at 22:52, Bruce Kellett wrote:
MWI simply formalizes the fact that such data are "in-principle
unknowable".
Well, usually we say that the SWE formalizes that fact, and that
the MWI interpret this in term of many world. But I am OK with
your statement, as SWE implies formally the MWI,
Statements like this are gaining in currency these days, but this
is strictly false. The SWE operating on vectors in Hilbert space
does not formally imply the MWI. All that the formalism implies
is the existence of superpositions. Schroedinger realized this
very early on, hence his example of the cat being in a
superposition of dead and alive states. Schroedinger thought this
was effectively a reductio ad absurdum for the wave equation.
I'm not so sure. I think he was more attacking the role of the
observer in creating reality. We see Einstein affirm this in a
letter to Schrodinger:
Einstein was most impressed with Schrödinger's paper, and in 1950
wrote Schrödinger a letter of praise, saying “You are the only
contemporary physicist, besides Laue, who sees that one cannot
get around the assumption of reality, if only one is honest. Most
of them simply do not see what sort of risky game they are
playing with reality—reality as something independent of what is
experimentally established. Their interpretation is, however,
refuted most elegantly by your system of radioactive atom +
amplifier + charge of gunpowder + cat in a box, in which the psi-
function of the system contains both the cat alive and blown to
bits. Nobody really doubts that the presence or absence of the
cat is something independent of the act of observation.”
Further, we see that later in his life, Schrodinger began to take
his theory (and the reality of the super position) more seriously:
“Schrödinger also”, David Deutsch notes, “had the
basic idea of parallel universes shortly before Everett, but he
didn't publish it. He mentioned it in a lecture in Dublin, in
which he predicted that the audience would think he was crazy.
Isn't that a strange assertion coming from a Nobel Prize winner—
that he feared being considered crazy for claiming that his
equation, the one that he won the Nobel Prize for, might be true.”
In order to get MWI one has to add a lot more superstructure. In
particular one has to solve the basis problem and give a
plausible account of the meaning of probabilities in a theory in
which every possible result actually occurs. Both of these areas
are still matters of substantial debate.
Tegmark shows in a large enough world, even under something like
the CI, you can't escape "all possibilities being realized", so
you're faced with the same probability "problem" whether you
think the wave function collapses or not: http://arxiv.org/abs/1008.1066
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.
if we define world by a structure of events close for
interaction. Then, using the FPI, we have a dterlministic and
local account of why the data appears for the observer first
person (plural) point of view as unknowable, indeterminist and
non local.
Maybe the data appear indeterministic and unpredictable in
principle because they really are that way -- the world is
governed by probabilistic laws. We don't actually need all the
superstructure of MWI.
What do you find more appealing, elegant, and historically more
likely to be true:
1. A large number of objects implied to exist by a simpler theory
2. A small or singular number of objects as described by a more
complex theory
MW is just what's left over when you dispense with the ill-
conceived and ill-defined notion of collapse: the only phenomenon
in all science that's not time-symmetric, not time-reversible,
nonlinear, discontinuous, non-deterministic, non-local, and
observer dependent. I'll take the many worlds before I take that.
But without solving the measure and basis problem, MWI doesn't
predict anything - or more accurately, it predicts everything.
MWI predicts the same as QM+collapse.
Only because it assumes the Born rule applies to give a probability
interpretation to the density matrix. But Everettista's either
ignore the need for the Born rule or they suppose it can be derived
from the SWE (although all attempts have fallen short).
Gleason's theorem (or simpler: Destouches-Février, or Finkelstein
(simplified in Selesnick's book) + the comp FPI + the SWE explains
the Born rule. (only problem: comp makes the SWE obligatory redundant,
so the only problem which remains is to extract the SWE, and modest
results go in that direction, where a priori it looks impossible, so
self-reference theory adds non trivial information in that search
already.
It is just that MWI dispense with magic. It is local,
deterministic, realist (even if multi-realist).
It simply pretends to dispense with collapse while sneaking in its
equivalent in order to use the Born rule.
It uses only the comp FPI, or variant. It is consciousness
selection, with relative measure.
But it assumes the Born rule provides the relative measure - which
is more than just the SWE. You can solve the problem of branch
counting by assuming infinitely many parallel worlds - but then that
raises the problem of defining "probability".
It is a continuum, and the probabilities are explained by what I
describe above.
It is radically non-local.
It appears to be so in each branches, but is not when you look at
all branches partition, and this in any base. Paper showing that
MWI is non local adds metaphysical baggage which is not in QM, nor
in Everett.
There are plenty of phenomenon in science that are non-linear.
Not in the reality, if the reality is described by quantum mechanics.
But QM is inconsistent with GR - so it is not a given that QM is
completely correct.
GR is inconsistent alone. QM makes it more consistent (cf Black holes
prevents the division by 0). Any way: I said "IF QM is correct".
But non linearity appearance is explained from inside + ignorance
of the other branches.
Computationalism is also discontinuous.
It depends of the topology. Computation = continuous with the
relevant toplogies of computer science. It is only discontinuous in
topology of reals, which is another subject.
The complaint was that wave function collapse is the only
discontinuous process in physics. But if you define different
topologies then it too is continuous in epistemological space (c.f.
quantum bayesianism).
?
I don't see any topology making the collapse continuous. It is not
even computable, not mentioning non local. That is why there are
theories like Bohm. The theory of Bohm does restore continuity, and
relative computability, but this makes its non-local character even
more weirdo: we need to abandon physical realism and/or special
relativity.
Bruno
Brent
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