On 2/9/2025 6:37 AM, John Clark wrote:
On Sat, Feb 8, 2025 at 6:06 PM Brent Meeker <meekerbr...@gmail.com> wrote:
/>>>Thus arbitrarily imposing a frequentist model on the
world by imagining an ensemble of universes. /
*>> Hugh Everett wasn't imagining, he was just taking seriously a
prediction that Schrodinger's Equation makes; *
/> Which is a very peculiar way of doing empirical science. /
*That's not peculiar for empirical scienceat all. We can't detect
virtual particles and we will never be able to, but physicists believe
they exist because they can explain how the Casimir Effect works and
why the electron has the magnetic moment that it has. And it's not
just in quantum mechanics. *
Virtual particles are just a mathematical tool to form infinite sums in
a consistent way. No physicist believes they exist.*
*
*We don't know if the entire universe is finite or infinite, or if
it's open or closed, but either way we do know that the entire
universe must be MUCH larger than the observable universe. *
So what? That doesn't mean supposing what is out beyond is the money
needed to balance your bank account.
*If the universe is open then it has negative curvature, and thus it
must be infinite because there cannot be an finite space with uniform
negative curvature without introducing boundaries and or singularities. *
*For a closed universe with a curvature of 0.4% (if it was larger than
that we would've already detected it and we haven't), the radius of
curvature would need to be _AT LEAST 160 times larger_ than the
observable universe's radius, which is 46.5 billion light years; 160 ×
46.5 billion= a radius of _7.4 trillion light years_ , and the
corresponding _minimum_ volume of the entire universe would be _25,600
times the volume_ of the observable universe. And there's more.
Although we can see galaxies that are now 46.5 billion light years
away, if they are further away than 17 billion light years
(corresponding to a time when the universe was about 500 million years
old) and we aimed a beam of light at it, that light would _NEVER_
reach the galaxy because relative to us space would be expanding
faster than the speed of light. *
/> Schroedinger actually had the same problem with QM; he saw that
"measurement" was not explained by the evolution of his equation./
*"Measurement" is not explained by Schrodinger's equation_IF_ you
assume that everything follows that equation _EXCEPT_ for a thing
called "the observer" which for some unknown reason obeys only
classical physics. *
*>> it's true that particular prediction can't be tested, but
many other predictions that the equation makes can be and
they've all passed with flying colors; *
/> Neglecting the point that all those other worlds have no
existence beyond showing up in mathematics as having a probability
bigger than zero and less than one./
*Paul Dirac thought the negative solutions that showed up in his
equation had no existence beyond showing up in his mathematics, but he
was wrong, it indicated the existence of antimatter. Dirac is later
quoted as saying that his equation was smarter than he was.*
*>> I see no reason why your default condition should be to
assume that other prediction is pure nonsense, especially
given the fact that it can explain why the quantum world is so
weird.*
>///I don't consider it "pure nonsense". /
*OK, I'm very glad to hear that! *
/> it doesn't actually explain the mechanism of worlds splitting,
as evidenced by Sean Carroll's answer to the question whether the
splitting is instantaneous across the universe or does it spread
out in some way at the speed to light? He says, "It doesn't
matter." So much for a better explanation. /
*Carrollis saying two things by that:*
*
*
*1) It's impossible even in theory to ever determine the answer to
that question. *
*
*
*2) The answer to that question is not important, that is to say it
makes no observable difference, and it's not even clear that the
question makes sense. *
*I believe both points are valid. Contrary to what some say, Einstein
didn't prove the Luminiferous Aether didn't exist, he proved it wasn't
important. *
> /It doesn't indicate how the Born rule is implemented in the
multiple worlds. /
*If there are multiple worldsthen, until you open the box, you don't
have enough information to be certain if you're in the world where the
cat is alive or in the world where the cat is dead, so you would have
to resort to probability; and if you're using Schrödinger's equation
the Born Rule is the only way to make sure the number you get is
between zero and one and all the probabilities add up to exactly one. *
/> Why doesn't your intuition just embrace probability and reflect
that probability means some things happen and other things don't. /
*Because Schrodinger's equation is deterministicso "/the atom just
happens to decay/" is an insufficient explanation. *
But all MWI does is push the insufficiency off to "you just happen to be
in the world where the atom decayed at 3:10pm"
*And because ifX and Y react with each other and then the result of
that reaction reacts with Z, I get one end result if I observe the X
and Y reaction and something completely different if I don't observe
it. Give me an intuitive explanation of how that could be without
using Many Worlds. And then give me an intuitive explanation of how
interaction free measurement could work without using Many Worlds. *
/> When you get a poker hand, do imagine all possible poker hands
were dealt in other worlds?/
*I could but in that particular case there are vastly simpler
computational means I could useto obtain a useful probability. The
situation would be very different if instead of cards you gave me a
sealed box and I had to bet if there was a live or dead cat in it. *
/> not every probability is based on ignorance./
*I think at the deepest level every probability _is_ based on
ignorance becauseI think Many Worlds is correct and all that Many
Worlds is saying is that Schrodinger's equation means what it says,
and Schrodinger's equation is 100% deterministic. If I always knew
what world I was in I would know if the cat was alive or dead before I
opened the box and I wouldn't need to resort to probability for anything.
*
I think you think MWI is correct simply because you don't know of any
alternatives. You have a cartoonish idea of Copenhagen and think of it
as the only alternative. A lot of other physicists, like me, think MWI
is no better than Copenhagen. It just pushes the problem off to more
obscure questions, like how does the orthgonality of worlds spread? And
why isn't Zeh's Darwinian decoherence enough? Here's a few papers which
discuss single-world solutions to the measurement problem. Don't bother
to read them though, they'll just perturb your certainty.
Collapse Miscellany
Philip Pearle
An introduction to the CSL (Continuous Spontaneous Localization) theory
of dynamical wave function collapse is provided, including a derivation
of CSL from two postulates. There follows applications to a free
particle, or to a `small' rigid cluster of free particles, in a single
wave-packet and in interfering packets.
https://arxiv.org/abs/1209.5082v2
Quantum Mechanics Without State Vectors
Steven Weinberg
It is proposed to give up the description of physical states in terms of
ensembles of state vectors with various probabilities, relying instead
solely on the density matrix as the description of reality. With this
definition of a physical state, even in entangled states nothing that is
done in one isolated system can instantaneously effect the physical
state of a distant isolated system. This change in the description of
physical states opens up a large variety of new ways that the density
matrix may transform under various symmetries, different from the
unitary transformations of ordinary quantum mechanics. Such new
transformation properties have been explored before, but so far only for
the symmetry of time translations into the future, treated as a
semi-group. Here new transformation properties are studied for general
symmetry transformations forming groups, rather than semi-groups.
Arguments are given that such symmetries should act on the density
matrix as in ordinary quantum mechanics, but loopholes are found for all
of these arguments.
arXiv:1405.3483v1
A Synopsis of the Minimal Modal Interpretation of Quantum Theory
Authors: Jacob A. Barandes, David Kagan
Abstract: We summarize a new realist interpretation of quantum theory
that builds on the existing physical structure of the theory and allows
experiments to have definite outcomes, but leaves the theory's basic
dynamical content essentially intact. Much as classical systems have
specific states that evolve along definite trajectories through
configuration spaces, the traditional formulation of quantum theory
asserts that closed quantum systems have specific states that evolve
unitarily along definite trajectories through Hilbert spaces, and our
interpretation extends this intuitive picture of states and
Hilbert-space trajectories to the case of open quantum systems as well.
Our interpretation---which we claim is ultimately compatible with
Lorentz invariance---reformulates wave-function collapse in terms of an
underlying interpolating dynamics, makes it possible to derive the Born
rule from deeper principles, and resolves several open questions
regarding ontological stability and dynamics
arXiv:1405.6754
Measurement and Quantum Dynamics in the Minimal Modal Interpretation of
Quantum Theory
Authors: Jacob A. Barandes, David Kagan
Abstract: Any realist interpretation of quantum theory must grapple with
the measurement problem and the status of state-vector collapse. In a
no-collapse approach, measurement is typically modeled as a dynamical
process involving decoherence. We describe how the minimal modal
interpretation closes a gap in this dynamical description, leading to a
complete and consistent resolution to the measurement problem and an
effective form of state collapse. Our interpretation also provides
insight into the indivisible nature of measurement--the fact that you
can't stop a measurement part-way through and uncover the underlying
`ontic' dynamics of the system in question. Having discussed the hidden
dynamics of a system's ontic state during measurement, we turn to more
general forms of open-system dynamics and explore the extent to which
the details of the underlying ontic behavior of a system can be
described. We construct a space of ontic trajectories and describe
obstructions to defining a probability measure on this space.
arXiv:1807.07136
I've listed only papers that are easily available on the arXiv. There
are others in older papers and books.
Brent
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