On 21-11-2022 01:28, Bruce Kellett wrote:
On Mon, Nov 21, 2022 at 2:52 AM smitra <smi...@zonnet.nl> wrote:
Probability cannot be a fundamental concept in physics as explained
here:
https://www.youtube.com/watch?v=wfzSE4Hoxbc
I'm afraid Deutsch is a bit too glib in this lecture. He hasn't,
despite his best efforts, removed probability from physics. For
example, in quantum mechanics, he has not explained why, if one
measures the z-spin of a spin-half particle prepared in an eigenstate
of x-spin, one gets only one result -- either z-spin-up or
z-spin-down. If one has eliminated probability, one should be able to
explain which result one gets, and why. It is no solution to say that
with many-worlds, that both results are obtained by disjoint copies of
the experimenter. The experimenter is just one copy, and one would
have to explain the result for each individual separately. Many worlds
does not explain why I, for example, see only z-spin-up and not
z-spin-down. To make sense of that, we need a viable concept of
probability and the Born rule.
Bruce
He has argued that fundamental physics cannot be based on probability,
it can at best play a role in an effective description of the physical
world. This excerpt is the most to the point:
https://www.youtube.com/watch?v=wfzSE4Hoxbc&t=1036s
He then goes on to argue that there is no need to refer to probabilities
in QM using a decision theoretic argument that does not refer to any
notion of a probability.
Saibal
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