On 7/31/2018 9:11 AM, Bruno Marchal wrote:
On 30 Jul 2018, at 22:27, Brent Meeker <[email protected]
<mailto:[email protected]>> wrote:
On 7/30/2018 9:58 AM, John Clark wrote:
>
/Forget collapse./
Many, perhaps most, physicists do exactly that because they believe
in the "Shut Up And Calculate" quantum interpretation and are only
interested in predicting how far to the right a indicator needle on
a meter moves in a particular experiment. But for some of us that
feels unsatisfying and would like to have a deeper understanding
about what's going on at the quantum level and wonder why there is
nothing in the mathematics that says anything about a wave collapsing.
That's not true. "The mathematics" originally included the Born rule
as part of the axiomatic structure of QM.
In the usual QM, yes. But this use a vague notion of observer, and a
seemingly forbidden process, a projection (a Kestrel!), I mean
forbidden if we apply the wave to the couple observer-particle.
Most of all they want to know what exactly is a "measurement" and
why it so mysterious.
The problem with the Born rule was that its application was ambiguous:
Ah! Exactly.
Where was the Heisenberg cut? Why was "the needle basis" preferred?
But decoherence theory has given answers (at least partially) to
those questions. Given those answers, one can just replace
"collapse" with "discard", i.e. discard all the predicted possible
results except the one observed. Is there really any difference
between saying those other predictions of the wf are in orthogonal,
inaccessible "worlds" and saying they just didn't happen. That seems
to be Omnes approach. He writes, "Quantum mechanics is a
probabilistic theory, so it only predicts probabilities.”
OK, but the honest, and perhaps naive inquirer would like to have an
idea about what are those probabilities about, and where they come from.
That was the source of resistance to Born's paper. Physicists assumed
that probability could only arise from ignorance of an ensemble. Since
there was no ensemble in Heisenberg's (or Schroedinger's) QM they
resisted the idea. Lots of attempts were made to reintroduce ensembles,
or at least virtual ensembles, so that they could feel comfortable with
having a probabilistic theory. Omnes' is just saying "Get over it!";
probabilities are fundamental. Everett's MWI is appealing to the same
intuition...that probabilities must refer to ensembles. So the ensemble
will be multiple-worlds. But that didn't really work because
Schroedinger's equation didn't predict multiple worlds with the right
ratios, it just gave real number probabilities. So people like Bohm and
Bruno invented infinite ensembles to explain the probability numbers.
Which is OK, but one should recognize that they are /*not */just
explicating Schroedinger's equation.
Brent
Now, the computationalists expected exactly that kind of
probabilities, on the computations, as the “step 3”, but mainly the
“step 4”, i.e. the unawareness of the basic computation “time” (the
number of steps in the universal dovetailing or the length of the
proof of a sigma_1 sentence),
It is all in head of the universal machine!
The existence of the universal machine is assured by Robinson
Arithmetic, or the combinator theory, as can been proved by all Löbian
combinators.
Bruno
Brent
--
You received this message because you are subscribed to the Google
Groups "Everything List" group.
To unsubscribe from this group and stop receiving emails from it,
send an email to [email protected]
<mailto:[email protected]>.
To post to this group, send email to [email protected]
<mailto:[email protected]>.
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
--
You received this message because you are subscribed to the Google
Groups "Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send
an email to [email protected]
<mailto:[email protected]>.
To post to this group, send email to [email protected]
<mailto:[email protected]>.
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
