"The Deutsch-Wallace-Everett programme can be understood as conceptually incoherent since its viability rests upon a notion of decoherence that conflicts with its own fundamental precepts with regard to both the subjective nature of probability, and the discrete nature of ontology. [..]
... elegant incoherence carries the highest risk of leading astray, and it is there, alas, that the seemingly revolutionary Deutsch-Wallace approach to Everettian quantum theory must be situated."
Many Worlds: Decoherent or Incoherent?
Yet another paper making the argument that many-worlds interpretations fail to reproduce the Born probabilities.
11 comments:
What does this paper really show?
The paper re-examines decoherence (p.7) and the removal of off-diagonal elements due to the environment FAPP. However, this removal is justified only if one already has the Born rule (p.8)
This circularity has been noticed by others before.
The authors notice that the Born rule has to be 'objective' to achieve this (because the Schroedinger evolution is deterministic).
However, Deutsch-Wallace claim to derive the Born rule as a 'subjective' probability using decision theoretic arguments *after* decoherence.
This is incoherent according to the authors (p. 11)
But rather to rely on my reading I recommend you read the paper for yourself.
I really wish I could read it and grasp it, but unfortunately I am little more than a informed layman.
Their argument certainly sounds sound, do you agree with their conclusion or do you find anything you disagree with in it?
I agree that 'many worlds' interpretations so far are incoherent.
Let's see if I understand the jist of it.
Wallace, Saunders, Deutsch and the "Oxford group" of Everettians rely on the decision-theoretic approach to derive the Born Rule.
This way of deriving the Born Rule has been labled as "bullshit" by quite a few authors over the years (A. Kent, H. Price, A. Rae and so on).
But *if* we pretend to accept the derivation, it is still not enough to help get FAPP and emergent worlds as Wallace suggests? Because decoherence relies on the same probability rule, which has to be objective and not subjective as in the Deutsch-Wallace derivation?
So not only is the derivation circular, but the application to decoherence makes it incoherent and flat out false ?
I would not use "flat out false" (and i think nobody uses "b.s." 8-)
1) we know p = 0 (or p very small) for every observer (this is what 'objectively' means).
2) now lets determine what the value of p is using decision theory (so we could in principle get different values for different observers, this is what 'subjectively' means).
'Incoherent' in this paper means we derive 2) by implicitly using 1)
Sure noone has used those terms, but they are basically saying the same thing ;P
And wouldn't "flat out false" be correct here?
If it's incoherent, how can it be anything other than completeley false?
I also noticed your post on the paper by Jan-Markus Schwindt about "nothing happening" in the Everettian interpretation.
Do you agree with it?
I mean if there are these 2 serious problems facing MWI, isn't it basically.. flat out wrong?
Yes, there are several problems with m.w.i. ...
Just to be clear there are also problems with other interpretations.
Btw I wrote some sort of overview previously: http://tsm2.blogspot.com/2010/02/interpretations-part-14.html
I understand that all interpretations have problems, or else I assume we'd already agree on which is true :)
Isn't it very likely that QM will be replaced with a more exact theory like Steven Weinberg foresees?
To me this seems natural given the current state of interpretations...
Re: MWI, do you think that the problems are insurmountable at the moment? From my layman POV I feel like these problems are permanent. I don't see for instance how they could suddenly find an objective born rule. Or how to define a basis without postulating anything other than the pure formalism?
I think the interpretation problem is in large part a deeper problem which physicists prefer to avoid ...
see: http://tsm2.blogspot.com/2012/08/scott-about-42.html
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