On 5/20/2018 2:54 PM, [email protected] wrote:
On Sunday, May 20, 2018 at 9:13:42 PM UTC, Brent wrote:
On 5/20/2018 1:44 PM, [email protected] <javascript:> wrote:
On Sunday, May 20, 2018 at 7:29:42 PM UTC, Brent wrote:
On 5/20/2018 3:47 AM, [email protected] wrote:
On Sunday, May 20, 2018 at 6:52:41 AM UTC, Brent wrote:
On 5/19/2018 8:19 PM, [email protected] wrote:
On Saturday, May 19, 2018 at 3:59:03 PM UTC, Brent wrote:
On 5/18/2018 10:53 PM, [email protected] wrote:
On Saturday, May 19, 2018 at 5:29:33 AM UTC, Brent
wrote:
On 5/18/2018 10:14 PM, [email protected] wrote:
*So why don't you draw the obvious inference?
If those other worlds don't exist -- which if
I can read English has been your passionate
position all along -- then quantum
measurements in this world, the only world,
are statistical and hence NOT reversible in
principle. AG*
but it is different in each branch of the
wave function, so reversing this branch
does nothing for the others, and does not
restore the original superposition. Thus
the process is irreversible in principle
(nomologically irreversible -- to reverse
violates the laws of physics).
*But if those other worlds don't exist, it
makes no sense whatever to rely on them to
establish irreversible in principle in this
world (as distinguished from statistically
irreversible or irreversible FAPP). It seems
you want to have it both ways; that many
worlds really don't exist. but quantum
measurements in this world are irreversible
in principle due the existence of many
worlds. AG*
You don't handle uncertainty well, do you.
Brent
You know, it's not a perfect analogy, but I don't
believe that when I pull the one arm bandit with
64 million possible outcomes, that 64 million
(minus one) worlds are created, each with an
identical copy of me, getting those other
outcomes. What do you believe? AG
I believe I'll wait for a better theory. One that
includes gravity and spacetime and consciousness.
Brent
I see. But you seem too ready to defend the MWI when it
appears to imply irreversible in principle. Or do you
accept Bruce's claim that the projection operator
implies irreversible in principle? AG
Either of them implies irreversiblity. Whether it is "in
principle" depends on what principle you invoke,
mathematics, practice, ...? MWI puts information in
orthogonal subspaces where we exist in copies such that
each copy can act only in one subspace and hence cannot
put together the information from other subspaces. A
projection operator is just a mathematical model of this
confinement to one subspace.
Brent
Please; no evasive games. We can forget about the MWI, given
its absurdity. Does, or does not the projection operator
imply irreversibility in principle as Bruce claims? AG
Sure, a projection operator throws away information so its
action is irreversible. If I project a star onto the
celestial sphere I preserve its longitude and latitude, but
it doesn't show how far away it is. That's why the MWI
advocates say projection conflicts with all the rest of
fundamental physics which is described by evolution that is
at least reversible in the mathematical sense.
Brent
But how do you know that the projection operator represents an
actual physical process? It could be just a bookkeeping device to
describe the fact that when many possible outcomes are possible,
we get a particular outcome.
Exactly. The quantum Bayesian take this view
How does "Baysian" fit into this picture? Can't one interpret the SWE
as a representation of what we know about a system, without being a
Baysian? AG
and consider Schroedinger's equation also as a personal book
keeping device of what one knows about a system and then the Born
rule and projection operators fit neatly into the scheme of
updating one's personal knowledge.
I would delete "personal" from your comment. We're referring to the
knowledge of any observer. AG
ISTM, that to argue for "irreversible in principle", it is
insufficient to appeal solely to the properties of the projection
operator. AG
Exactly what led to Everett, MWI, and decoherence theory. But at
the price of having multiple, orthogonal "worlds" to explain the
appearance of randomness. Of course some people hate randomness
and are quite happy to have multiple worlds instead.
Looks like I am in the decoherence camp; namely, that when a quantum
measurement occurs, entanglements with reservoir states somehow
suppresses all outcomes but one
But that "somehow" is the magic of the Copenhagen interpretation.
Decoherence is the process of making subspaces (worlds) orthogonal, but
it doesn't choose one and "suppress" (vanish?) the others. The all
continue to exist and to be orthogonal.
, and the process is statistically irreversible (irreversible FAPP)
since all entanglements are reversible (or do they run amok of Bell's
theorem?). I can't prove it of course, but it seems like the most
sober, conservative assumption given the choices. What I object to
about Bruce's approach, is that he simply claims "irreversible in
principle" based on the projection operator, and won't admit it's just
his opinion, or else make a real effort to argue it. It's like he now
sees himself as the *Oracle from Australia*. AG
I objected to the "in principle" because there are different possible
principles. Is the information just gone, as in CI. Or is it put into
subspaces that are statistically orthogonal (i.e. FAPP) and therefore
beyond any physical reversal, but still experssed by reversible mathematics.
Brent
Brent
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