On 11 Oct 2013, at 03:25, meekerdb wrote:
So there are infinitely many identical universes preceding a
measurement. How are these universes distinct from one another?
Do they divide into two infinite subsets on a binary measurement, or
do infinitely many come into existence in order that some branch-
counting measure produces the right proportion? Do you not see any
problems with assigning a measure to infinite countable subsets (are
there more even numbers that square numbers?).
And why should we prefer this model to simply saying the Born rule
derives from a Bayesian epistemic view of QM as argued by, for
example, Chris Fuchs?
If you can explain to me how this makes the parallel "experiences",
(then), disappearing, please do.
When I read Fuchs I thought this: Comp suggest a compromise: yes the
"quantum wave" describes only psychological states, but they concern
still a *many* dreams/worlds/physical-realities, including the many
self-multiplication.
It is still Everett wave as seen from inside.
We just don't know if the dreams defined an unique (multiversal)
physical reality. Neither in Everett +GR, nor in comp.
Bayesian epistemic view is no problem, but you have to define what is
the knower, the observer, etc. If not, it falls into a cosmic form of
solipsism, and it can generate some strong "don't ask" imperative.
Bruno
Brent
On 10/10/2013 6:11 PM, Pierz wrote:
I'm puzzled by the controversy over this issue - although given
that I'm not a physicist and my understanding comes from popular
renditions of MWI by Deutsch and others, it may be me who's missing
the point. But in my understanding of Deutsch's version of MWI,
the reason for Born probabilities lies in the fact that there is no
such thing as a "single branch". Every branch of the multiverse
contains an infinity of identical, fungible universes. When a
quantum event occurs, that set of infinite universes divides
proportionally according to Schroedinger's equation. The appearance
of probability arises, as in Bruno's comp, from multiplication of
the observer in those infinite branches. Why is this problematic?
On Saturday, October 5, 2013 2:27:18 AM UTC+10, yanniru wrote:
Foad Dizadji-Bahmani, 2013. The probability problem in Everettian
quantum mechanics persists. British Jour. Philosophy of Science
IN PRESS.
ABSTRACT. Everettian quantum mechanics (EQM) results in ‘multiple,
emergent, branching quasi-classical realities’ (Wallace [2012]).
The possible outcomes of measurement as per ‘orthodox’ quantum
mechanics are, in EQM, all instantiated. Given this metaphysics,
Everettians face the ‘probability problem’—how to make sense
of probabilities, and recover the Born Rule. To solve the
probability problem, Wallace, following Deutsch ([1999]), has
derived a quantum representation theorem. I argue that Wallace’s
solution to the probability problem is unsuccessful, as follows.
First, I examine one of the axioms of rationality used to derive
the theorem, Branching Indifference (BI). I argue that Wallace is
not successful in showing that BI is rational. While I think it is
correct to put the burden of proof on Wallace to motivate BI as an
axiom of rationality, it does not follow from his failing to do so
that BI is not rational. Thus, second, I show that there is an
alternative strategy for setting one’s credences in the face of
branching which is rational, and which violates BI. This is Branch
Counting (BC). Wallace is aware of BC, and has proffered various
arguments against it. However, third, I argue that Wallace’s
arguments against BC are unpersuasive. I conclude that the
probability problem in EQM persists.
http://www.foaddb.com/FDBCV.pdf
Publications (a Ph.D. in Philosophy, London School of Economics,
May 2012)
‘The Probability Problem in Everettian Quantum Mechanics
Persists’, British Journal for Philosophy of Science, forthcoming
‘The Aharanov Approach to Equilibrium’, Philosophy of Science,
2011 78(5): 976-988
‘Who is Afraid of Nagelian Reduction?’, Erkenntnis, 2010 73:
393-412, (with R. Frigg and S. Hartmann)
‘Confirmation and Reduction: A Bayesian Account’, Synthese,
2011 179(2): 321-338, (with R. Frigg and S. Hartmann)
His paper may be an interesting read once it comes out. Also
available in:
‘Why I am not an Everettian’, in D. Dieks and V. Karakostas
(eds): Recent Progress in Philosophy of Science: Perspectives and
Foundational Problems, 2013, (The Third European Philosophy of
Science Association Proceedings), Dordrecht: Springer
I think this list needs another discussion of the possible MWI
probability problem although it has been covered here and elsewhere
by members of this list. Previous discussions have not been
personally convincing.
Richard
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