On Wed, Feb 25, 2015 at 5:28 AM, Bruce Kellett <[email protected]
<mailto:[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.
