[extropy-chat] Many worlds and Hugh Everett

[Dirk Bruere]

----- Original Message ----- 
From: "scerir" <scerir at libero.it>
To: "Dirk Bruere" <dirk at neopax.com>; "ExI chat list"
<extropy-chat at lists.extropy.org>
Sent: Tuesday, December 30, 2003 7:59 PM
Subject: Re: [extropy-chat] Many worlds and Hugh Everett


> > As it stands the [MWI] interpretation can only be verified
> > subjectively, and only if true.
> > Dirk
>
> There are several different "interpretations", or "models",
> or "theories", not just one QM. And they are not equivalent,
> in physical terms, i.e., the energy conservation law in MWI
> is a statistical law; i.e., the von Neumann density operator
> depends on the specific subjects performing measurements
> on the same system (the "whose knowledge?" issue); etc.

The point is though, that there are no (currently) testable QM theories that
both make different predictions from standard QM and are not already
falsified by experiment.

> There are measures, probabilities, entropies, informations,
> effects dependent on the specific "interpretation" you choose:

None of which are distinguishable experimentally.

> Physical collapse interpretation, Copenhagen interpretation,
> decoherence and environment interpretation, conditional density
> matrices, two-state time symmetrical quantum formalism, instantaneous
> non-local influences, superluminal influences, Eberhard's superluminal
> "realistic" influences, retro-causality models, modal interpretations,
> consistent histories, consciousness, non-local hidden variables,
> witnessing interpretations, superselection rules, modified or
> non-linear dynamics, statistical interpretation of (proper and
> improper) mixtures, Einstein's statistical interpretations, GWR theory,
> Brownian quantum theory, Ne'eman's geometric interpretation,
> Finkelstein's physics of logic interpretation, Bell's iper-deterministic
> interpretation, Bohmian mechanics, Barut's mechanics, MWI, Hugh Everett,
> many minds, Pitowsky's reformulation of a local hidden variable theory
> based on the Banach-Tarski theorem, quantum diffusion theory,
> Ithaca interpretation, informational interpretation(s), etc. etc.).
>
> One of the reasons is that QM (complete or not, in the sense of EPR)
> in general (excepting perhaps MWI) is assumed not to be a "closed"
> theory, even if it pretends to be universally valid.
> As Bohr stated, since the very beginning of QM, the "observer",
> measuring a quantum system by means of an "apparatus", remains out,
> it is not described by QM. This is the von Neumann "cut", this is
> one of the mysteries, this is the source of (many of) the above
> "interpretations", or "theories". Although QM would describe
> anything, it cannot include everything, and it must introduce
> a "cut", an "interface", somewhere, from which the probability
> rules can be derived. As you have maybe already realized there are,
> perhaps, also Goedelian issues in QM, because the theory is not
> closed, it is not self-supporting. These issues are many, i.e.
> the subject-object separability is unclear (Albert-Peres self-
> measurements, Finkelstein's 'introspective' systems); i.e., it is
> well known the fact that linear combinations of "elements of reality",
> as defined by EPR, may not be themselves "elements of reality",
> thus also the mathematical framework of QM (but not the experimental)
> seems to be "fuzzy". About all that, and many more, see, in example,
> T.Breuer at http://www.staff.fh-vorarlberg.ac.at/tb/tbpublisteengl.html

Well, I tend to agree that the measurement problem lies at the heart of any
interpretation, but again, there are no experiments which have thrown
existing formalism into doubt.

> But, on the experimental side, a lot of work has been done, and now
> the situation is much different from that described by Bohr
> (a realist, but "sui generis"), and von Neumann (the "cut"), and
> London and Bauer and Wigner and the young Heisenberg (the
> "consciousness"), and Pauli (the "occasio", or "creation").
> Now quantum macro-objects are under direct "investigation",
> and the Nobel laureate A. Leggett wrote this interesting paper
> www.nobel.se/physics/symposia/ncs-2001-1/leggett.pdf
> against the "macro-realism", as he calls it. We could say
> that the observer and the apparatus are, thus, close to
> become objects of performed physical experiments.

...but still no suprises.

> It is important to remember here the precise domain of validity
> of Bell's theorem. Its proof requires the observed system to be
> *deterministic*, while the observer is *not*. (As Bell himself
> realized, if the observer too is deterministic, there is no problem
> at all with QM, and local hidden variables, because everything
> would be pre-determined, our free will be entangled with quantum
> systems, by a totalitarian conspiratorially theory). Thus Bell's
> theorem, requiring determinism and direct counterfactual reasoning
> (if we would measure ... if instead we would measure ...) has a
> limited validity within a theory based on intrinsic randomness and
> indeterminism.
>
> As you maybe already realized, if you wish to disprove QM,
> or one of its "interpretations", you have many different
> narrow "avenues".

None of which have led anywhere to date.

> I do not agree with the usual song that if you want to disprove
> MWI you must just disprove QM. That is a bit simplistic. Because,
> in example, we can schrink the entire QM into a set of 5 or 6 axioms,
> with are robust indeed.


OK.
Given the physical equivalence of the various interpretations does that mean
quantum suicide experiments will have the same outcome?

> Being MWI (or MWI + decoherence) a "realistic" theory, in the sense
> of EPR (*), if you wish to disprove this theory you could start
> from a precise criterion (still to be invented, to my knowledge)
> to distinguish, by performing experiments, a coherent superposition
> of states, from a (proper or improper) mixture of states.
>
> Algorithmic information theory could provide some insight here.
> And also some new development of the theory of entanglements.
> (For mixed states, it is harder to establish a good measure of
> entanglement, since such a measure has to distinguish between
> entropy arising from classical correlations in the state, and
> entropy due to purely quantum correlations. Two measures of entanglement
> that have explicit physical meaning in the processing of quantum
> information have emerged, the entanglement cost of a quantum state and
> the distillable entanglement of a quantum state).
>
> s.
>
> (*) ""if, without in any way disturbing a system, we can predict
> with certainty (i.e. with probability equal to unity) the
> value of a physical quantity, then there exists an element
> of physical reality corresponding to this physical quantity."
> >From the specific point of view of MWI, the statement above
> is perfectly right, true, valid, consistent. (From the MWI
> pov EPR were a bit incorrect, regarding the specific observables
> whose values can be predicted).


Dirk

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