On 25 Feb 2015, at 12:28, Bruce Kellett 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.
The formalism implies the superposition, and the fact that the
superposition are contagious to what observe the superposed state, in
the basis of the superposed states. This implies the many worlds, with
"world" defined by the closure for interaction.
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.
Like EPR was conceived as a reductio ad absurdum for completeness of
the wave equation.
In order to get MWI one has to add a lot more superstructure.
I don't think so, except the definition of worlds, but with
computationalism we already know that there is no worlds, but
remlative histories, dreams or states. MWI does not solve all
problems, only a lot.
Collapse theories have to add superstructure; like Bohm Potential, or
a consciousness reducing wave packet, or mysterious action at a
distance.
In particular one has to solve the basis problem
I disagree. It seems to me that Everett already solved it. The
relative subjective state does not depend on the base. Of course the
history of our body and brains shows that our consciousness is
selected with remlative states distinguishible in the position base,
but that is more historical than fundamental (except Zurek porvides
some explanation why position was well suited for having something
like interacting machines).
and give a plausible account of the meaning of probabilities in a
theory in which every possible result actually occurs.
But this is what I did, even before I knew QM or Everett. This is
solved in arithmetic, by computationalism, and this implies a many-
dream (say) interpretation (say) of arithmetic, and QM confirms this
aspect.
Both of these areas are still matters of substantial debate.
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.
Either the superposition are contagious (SWE), or not (SWE +
collapse), but the collapse is the kind of "superstructure" which is
really weird: it entails physical indeterminacy (events without cause,
that is "miracle"), spooky action at a distance (which kills either
physical realism or relativity theory), non computationalism, etc.
But my point is that with just computationalism (being neutral on all
physical theory as long as ythey permit Turing machine to work), we
have already an explosion of relative states, and a measure problem.
That measure problem (the comp one, not the Quantum one) is solved by
such an explosion of histories/computations, so the MWI is rather a
good news. We can say, "Oh, we already knew". With some luck, QM *is*
the solution of the computationalist mind-body problem.
That is testable, either the logic Z gives the quantum logic, or not.
This has to be nuanced by the fact that there are more than one
quantum logic, and comp proposed more than one candidate for those
quantum logics (S4Grz1, Z1*, X1*).
An evidence for a physical collapse of the wave would be a blow in
computationalist philosophy.
Bruno
Bruce
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