From: *Jason Resch* <[email protected]>
On Sun, Jun 17, 2018 at 6:42 AM, Bruce Kellett
<[email protected]> wrote:
From: *Jason Resch* <[email protected]
<mailto:[email protected]>>
On Sun, Jun 17, 2018 at 12:12 AM, <[email protected]> wrote:
* why do you prefer the MWI compared to the Transactional
Interpretation? I see both as absurd. so I prefer to assume
the wf is just epistemic, and/or that we have some holes in
the CI which have yet to be resolved. AG *
1. It's the simplest theory: "MWI" is just the Schrodinger
equation, nothing else. (it doesn't say Schrodinger's equation
only applies sometimes, or only at certain scales)
Well no, it is an interpretation of the SE, involving the
reification of the wave function. So it is not 'just' the
Schrödinger equation.
It is a theory, in that it is fully mathematical and makes
predictions. Other so called interpretations CI etc. are not
mathematical theories because they don't say when or why or under what
circumstances Schrodinger's equation stops working. As Max Tegmark said:
“I disagree that the distinction between Everett and Copenhagen is
‘just interpretation’. The former is a mathematical theory, the latter
is not. The former says simply that the Schrödinger equation always
applies. The latter says that it only applies sometimes, but doesn't
given an equation specifying when it doesn't apply (when the so-called
collapse is supposed to happen). If someone were to come up with such
an equation, then the two theories would be mathematically different
and you might hope to make an experiment to test which one is right.”
Decoherence theory effectively answers such objections.
You speak of reification of the wave function as if it is something
special. In what other physical theory is something postulated one
theory, and a different theory is when that same thing is postulated,
but is also "really real"? Is the theory of quarks distinct from
another theory of quarks that holds them to be really real?
David Deutsch comments on the absurdity of this:
“Schrödinger also”, David Deutsch notes, “had the basic idea of
parallel universes shortly before Everett, but he didn't publish it.
He mentioned it in a lecture in Dublin, in which he predicted that the
audience would think he was crazy. Isn't that a strange assertion
coming from a Nobel Prize winner—that he feared being considered crazy
for claiming that his equation, the one that he won the Nobel Prize
for, might be true.”
Schrödinger was also the originator of the idea of a collapse of the
wave function. He saw that his wave function necessitated a collapse of
his wave to a point particle interaction in the majority of measurements.
2. It explains more while assuming less (it explains the
appearance of collapse, without having to assume it, thus is
preferred by Occam's razor)
Maybe the collapse is real.
But to assume this is like assuming there are invisible and
undetectable "motive demons" operating within a car engine that are
necessary to make the car engine work, when we have another perfectly
valid way of explaining everything the car engine does without having
to assume these motive demons. I don't see the point when we have a
theory that explains all the facts before us.
Maybe it just means that we don't yet fully understand the collapse.
There are plenty of possibilities that don't resort to magic.
3. Like every other successful physical theory, it is linear,
reversible (time-symmetric), continuous, deterministic and does
not require faster than light influences nor retrocausalities
MWI is still a non-local theory. FTL influences or not, QM is
intrinsically non-local.
When you say non-local what type of non-locality do you mean? It is a
local theory in the sense that physical objects interact only with
other physical objects in their proximity, and carry information only
at luminal or subluminal speeds. See Q12 on
http://www.anthropic-principle.com/preprints/manyworlds.html
Price's argument here has been shown to be invalid -- he surreptitiously
relies on non-locality.
4. Unlike single-universe or epistemic interpretations, "WF is
real" with MWI is the only way we know how to explain the
functioning of quantum computers (now up to 51 qubits)
Rubbish. The functioning of quantum computers is not dependent on
MWI. Many worlds is, after all, only an interpretation. Not the
reality of anything at all.
How do you explain the finite computational resources of a table-top
quantum computer factoring a prime number in seconds when it would
take a classical computer the size of the solar system 10^100 years to
do the same calculation?
David Deutsch notes that quantum computers present a strong challenge
to defenders of single-universe interpretations, saying “When a
quantum computer delivers the output of such a computation, we shall
know that those intermediate results must have been computed
somewhere, because they were needed to produce the right answer. So I
issue this challenge to those who still cling to a single-universe
world view: if the universe we see around us is all there is, where
are quantum computations performed? I have yet to receive a plausible
reply.”
That might be Deutsch's opinion, but plenty of others think differently.
Quantum computers can easily be understood in a single world account.
5. Unlike copenhagen-type theories, it attributes no special
physical abilities to observers or measurement devices
Which version of the CI are you referring to? There are as many
"Copenhagen Interpretations" as there are citizens of Copenhagen.
Bohr's original theory did not refer to observers or make
experiments central. He merely thought that quantum phenomena were
understandable only in the context of a classical world.
By CI theories here, I mean those that include collapse of the wave
function (an irreversible, random, instantaneous event) being
triggered by some nebulously defined measurement, observation,
consciousness, etc.
Most of these objections to CI are answered by decoherence theory.
6. Most of all, theories of everything that assume a reality
containing all possible observers and observations lead directly
to laws/postulates of quantum mechanics (see Russell Standish's
Theory of Nothing
<http://www.hpcoders.com.au/theory-of-nothing.pdf>, Chapter 7 and
Appendix D).
Unfortunately, Russell's attempt to derive quantum mechanics from
the plenum of all possible bit strings failed at the first step.
So you don't have much support from this.
I would be very interested to see this, do you recall the subject or
time frame of this discussion?
Not off-hand. But you could search the archives of this list. It was
probably late last year that we had this discussion.
In any case, if Russell's derivation failed, there are other results
that are other clues (e.g. from Bruno's UDA) which from the assumption
of an infinite reality predicts several quantum phenomenon, including
apparent randomness, non-clonability of matter, and evidence of
infinite computations at work when we look at sufficiently small scales
Bruno's so-called successful predictions of quantum phenomena are no
more than clutching at straws. He has not derived any sensible physics.
Given #6, we should revise our view
But we don't have #6. See the discussion I had with Russell on
this list some time ago. He had to admit that his derivation of QM
failed.
It is not MWI and QM that should convince us of many worlds, but
rather the assumption of many worlds (an infinite and infinitely
varied reality) that gives us, and */explains /*all the weirdness
of QM.
No, the weirdness of the violation of the Bell inequalities and
non-locality remains, even in MWI.
Bell had an implicit assumption in his reasoning, which is that only a
single definite result is obtained by all parties for any given
measurement (including those not performed). This is not true under
MWI so Bell's reasoning that there must be non-locality fails for MWI,
as many-worlds lacks contra-factual definiteness.
Again from:
http://www.anthropic-principle.com/preprints/manyworlds.html
<http://www.anthropic-principle.com/preprints/manyworlds.html>
*To recap. Many-worlds is local and deterministic. Local measurements
split local systems (including observers) in a subjectively random
fashion; distant systems are only split when the causally transmitted
effects of the local interactions reach them. We have not assumed any
non-local FTL effects, yet we have reproduced the standard predictions
of QM.*
*So where did Bell and Eberhard go wrong? They thought that all theories
that reproduced the standard predictions must be non-local. It has been
pointed out by both Albert [A] and Cramer [C] (who both support
different interpretations of QM) that Bell and Eberhard had implicity
assumed that every possible measurement - even if not performed - would
have yielded a *single* definite result. This assumption is called
contra-factual definiteness or CFD [S]. What Bell and Eberhard really
proved was that every quantum theory must either violate locality *or*
CFD. Many-worlds with its multiplicity of results in different worlds
violates CFD, of course, and thus can be local.*
As I said above, Price has an invalid argument. If Bell's theorem does
not apply to MWI, why is it that no one has been able to give a simple,
clear, local account of the violations of the Bell inequalities? Maudlin
concludes his discussion of many worlds by questioning whether sense can
be made of correlations if all outcomes occur at both ends of a
Bell-type experiment. He concludes: "If some sense can be made of the
existence of correlations, we have to understand how. In particular, if
appeal is made to the wave-function to explicate the sens e in which,
say, the "passed" outcome on the right is paired with the "absorbed"
outcome on the left to form a single "world", then we have to recognize
that this is not a /local/ account of the correlations since the
wave-function is not a local object. (Quantum Non-Locality & Relativity,
3rd Edition.)
This should overwhelmingly convince us of MWI-type everything
theories over any single-universe interpretation of quantum
mechanics, which is not only absurd, but completely devoid of
explanation. With the assumption of a large reality, QM is made
explainable and understandable: as a theory of observation within
an infinite reality.
I think other possibilities are still available, and generally
more acceptable.
MWI has problems of its own. Particularly with the preferred basis
problem and the derivation of Born's rule from within many worlds
in a non-circular way.
Other theories don't even offer an explanation for Born's rule. MWI
at least offers several plausible answers, such as Gleason's Theorem.
Gleason's theorem is not the complete answer to the origin of the Born rule.
Regarding preferred bases, both of the papers I provided which began
this thread address that question:
https://arxiv.org/pdf/1104.2324.pdf <https://arxiv.org/pdf/1104.2324.pdf>
* Note that quantum interferences between different terms in Eq.
(39) are extremely small, since overlaps between macroscopically
different configurations, such as and , are suppressed by
the huge dimensionality of the corresponding Hilbert space. In
fact, for any observables constructed out of local operators,
matrix elements between macroscopically distinct states are highly
suppressed, This, therefore, provides preferred bases for any
macroscopic systems.*
and
https://arxiv.org/pdf/1105.3796.pdf <https://arxiv.org/pdf/1105.3796.pdf>
*Decoherence Decoherence1 explains why observers do not experience
superpositions of macroscopically distinct quantum states, such as
a superposition of an alive and a dead cat. The key insight is
that macroscopic objects tend to quickly become entangled with a
large number of “environmental” degrees of freedom, E, such as
thermal photons. In practice these degrees of freedom cannot be
monitored by the observer. Whenever a subsystem E is not
monitored, all expectation values behave as if the remaining
system is in a density matrix obtained by a partial trace over the
Hilbert space of E. The density matrix will be diagonal in a
preferred basis determined by the nature of the interaction with
the environment*
*This preferred basis is picked out by the apparatus
configurations that scatter the environment into orthogonal
states. Because interactions are usually local in space, ρSA will
be diagonal with respect to a basis consisting of approximate
position space eigenstates. This explains why we perceive
apparatus states |0iA (pointer up) or |1iA (pointer down), but
never the equally valid basis states |±iA ≡ 2 −1/2 (|0iA±|1iA),
which would correspond to superpositions of different pointer
positions.*
That is just the explanation that Schlosshauer gives. And as I have
pointed out, it is circular. One could justify any Quantum operator at
all as the position operator on this basis -- physics would be
different. But then, what is required is an account of why physics is as
it is.
Bruce
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