On 11/17/2017 8:35 PM, [email protected] wrote:
On Friday, November 17, 2017 at 7:18:23 PM UTC-7, Brent wrote:
On 11/17/2017 6:08 PM, [email protected] <javascript:> wrote:
On Friday, November 17, 2017 at 6:41:43 PM UTC-7, Brent wrote:
On 11/17/2017 4:04 PM, [email protected] wrote:
On Friday, November 17, 2017 at 2:38:40 PM UTC-7, Brent wrote:
On 11/17/2017 1:17 PM, [email protected] wrote:
*I think "must" is unwarranted, certainly in the case
of the MWI. Rather, it ASSUMES all possible
measurements must be realized in some world. I see no
reason for this assumption other than an insistence to
fully reify the wf in order to avoid "collapse". Same
situation in String Theory; no "must"; simply other
possible universes in the landscape. Do you really
think that when you pull a slot machine and get some
outcome, the 10 million other possible outcomes occur
in 10 million other universe? Seems ridiculous to me.*
The problem is a conflict:
(1) If the wave-function collapses when does it do it
and what is the process.
*The fact that we have unsolved problems, does not suggest
we should grasp as straws such as the MWI. *
Does a human being have to look at the record? Is
simply having a recorde enough? But then what
constitutes a record? Does it have be made of more than
100 atoms, more than 10, more than 1? How is the record
created, if not by evolution of the Schrodinger equation?
*If you consider a specific experiment, say the double slit
using micro objects like electrons, all you need is a
recorder, any recorder, and if it is designed to determine
which-way, the interference is destroyed. Thus, you don't
need humans or consciousness in any form to collapse the wf.
Feynman discusses this and it's quite conclusive IMO.
*
But you need to "collapse" it somehow by measuring the
position of the electrons - otherwise there is no
interference pattern. So the question remains, what is a
measurement? If you replace the film by an array of atoms
and you plan to measure where the electron lands by which
atom it strikes and ejects from the array, you will them have
to make a second measurement to see which atoms are missing.
So "measurement" must include more interaction than that;
enough interaction to constitute a "record". But that seems
to just reword the problem. How much of a "record"? and what
constitutes a record?
*I think these details can be worked out on a case-by-case basis.
But the main point seems solid; no human observers or
consciousness needed to produce interference, which is tantamount
to collapse. Do you agree to that? AG
*
I agree that a human observer is not necessary...even a Trump
supporter would suffice.
(2)If it's created by a splitting of the world, then you
still have the same questions with "splitting" in places
of "collapse" except that the SE does provide the
evolution. But then in the Schrodinger cat experiment
the world is splitting */continuously/*.
*
*
*IMO, the problem posed by the cat is a macro object in an
unthinkable superposition of Alive and Dead simultaneously.
But if the object is macro, won't the interference terms be
vanishingly small, so small that the unthinkable conclusion
does not occur in the lifetime of the universe? IOW, FAPP
there is no superposition and thus no enigmatic superposition.*
Forget the cat. It's the radioactive atom whose emission
will break the vial that causes the continuous splitting of
the world: decay at 0:00...0:01...0:02.... And is FAPP
enough? There are going to be intermediate cases in which
there are 10 dof instead 1e30 dof, and the superposition can
be eliminated by a change of basis.
*
*
*FAPP is probably not enough. What is the change of basis that
eliminates the superposition? For the singlet state, Bruce says
there is none and that I may have misunderstood your earlier
comments that every superposition can be eliminated by a change
of basis. TIA, *
No, Bruce was thinking of what /*local */operator could be
implemented. In theory any pure state can be an element of a
basis. So if the superposition is pure it will an eigenstate of
some operator....although in general it will often be one that is
impractical to implement.
Brent
*
*
*If you can remove the superposition from any pure state by a change
of basis, *
Just because one exists doesn't mean you can determine what it is. The
no-cloning theorem says there is no measurement by which you can
determine the state of an arbitrary system.
*why not do it for the cat and maybe the problem will go away? AG
*
Because the cat, being macroscopic, doesn't have a pure state. The cat
/plus everything the cat is entangled with/ has a pure state, but that
is an impossibly complex and growing system. Even for a small system
for which we might be able to calculate its orthonormal basis states
(e.g. all the excited modes of a water molecule) it will generally be
impossible to construct an apparatus that will measure in that basis.
The basis we can actually measure in will generally include averaging
over some of the excitations.
Brent
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