On 16/11/2017 9:14 am, Russell Standish wrote:
On Wed, Nov 15, 2017 at 10:54:51PM +1100, Bruce Kellett wrote:
On 15/11/2017 5:02 pm, Russell Standish wrote:
On Wed, Nov 15, 2017 at 02:46:21PM +1100, Bruce Kellett wrote:
I said "one of the strongest"! I know that you want to define QM from the
idea of observer moments. I don't think that this will work, and the usual
consensus is that one of the strengths of MWI is the elimination of the
conscious observer.
Where's your evidence that this is the usual concensus? Who argues for it?
Most people, indirectly if not directly. I am thinking of MWI proponents
such as Deutsch and Wallace. Wallace puts it like this "Some have argued
that he measurement problem of quantum mechanics gives us reason to abandon
the picture of science as describing an observer-independent world....". He
does not accept this view. The general view of scientific realism consists
in the belief that the objective external world is independent of the
observer. The thinking is related to Bell's assertion that: "Measurement
should never be introduced as a primitive process in a fundamental
mechanical theory like classical or quantum mechanics..." Measurement,
observation, observers are all related concepts in this context.
Deutsch, I could believe would argue that. But Wheeler would be a
counter to that. I'm not that familiar with Wallace.
Wallace is a collaborator with Deutsch. I don't know what Wheeler would
say here> I think he was a believer in scientific realism -- reality
without an observer. But then, head counts don't really amount to much.
A conscious observer (or rather just observer, really) is still
required to define the branches of the MWI, be that mediated by Zeh's
decoherence process, or otherwise. To eliminate observers entirely
requires solving the preferred basis problem without reference to an
observer or observation.
That is not true. The basis problem is solved by Zurek's einselection -- the
preferred basis is the one that is stable against further
decoherence.
I understand that the idea of einselection is still rather
controversial,
Not really. See Schlosshauer's paper and book.
I haven't really followed the literature, but it strikes me that
problem is that ultimately einselection is not a unitary process, so
it has to be considered as the result of some sort of coarse graining
(which is, of course, due to the actions of the observer discretising
a continuous world), in much the same way as the second law of
thermodynamics emerges from a strictly reversible microscopic
dynamics.
That is not correct. einselection is entirely unitary. It is closely
related to the nature of the interaction Hamiltonian between the system
and the environment. There is no collapse involved. It is a question of
stability against further decoherence rather than anything else.
I find it intriguing that the recent critique of Einselection by
Kastner is entitled "`Einselection' of Pointer Observables: the new
H-Theorem". The H-Theorem, as I'm sure you know, but for the benefit
of other lurkers is Bolzmann's mechanism of deriving the second law
from coarse graining the revrsible microscopic dynamics.
I am not familiar with this argument, but if he related einselection to
coarse graining, then he has missed the point.
Bruce
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