On 11/18/2024 6:38 PM, PGC wrote:
On Monday, November 18, 2024 at 11:37:16 PM UTC+1 Brent Meeker wrote:
On 11/18/2024 5:53 AM, John Clark wrote:
...
*The useful role that Many Worlds provides is that it doesn't
need to explain what a "measurement" or an "observer" is*
LOL. You just wrote three paragraphs immediately above each of
which referred to "observed". So if it doesn't need an
explanation it must be obvious and have the same meaning as in the
neo-Copenhagen interpretation, NCI. MWI needs to explain how and
when the worlds split, presumably due to decoherence although I've
not seen an explicit calculation of an instance of the process.
The same when and how is available to NCI if you think it needs one.
I find myself seeking clarification regarding your statements, Brent.
E.g. about the absence of explicit calculations for the process of
branching in MWI. This surprises me, as the phenomenon of decoherence,
as you well know, has been extensively studied both theoretically and
experimentally. The literature is abundant with models demonstrating
how interactions between quantum systems and their environments
suppress interference, leading to the emergence of classical behavior.
Then it will be easy for you to cite a few. The ones I find like
arxiv2406.15577 are not very satisfactory
"Unfortunatey, it seems much more complicated to explain the behaviour
for cases (ii) and (iii). Certainly, owing to the extensive number of
conserved quantities, the states |ψ(x)⟩ can not explore the available
Hilbert space in an unbiased fashion, which causes deviations from the
behaviour of typical states. Yet, why the exponent α(T) becomes even
smaller for larger T remains a mystery."
These calculations provide the empirical foundation for many
interpretations of quantum mechanics, including MWI.
If your critique is that these calculations do not explicitly prove
the branching described by MWI, I would consider that a valid
philosophical concern, but not necessarily a deficiency of the
calculations themselves, which are separate and agnostic regarding
interpretation. In MWI, branching is not an additional mechanism;
rather, it is a natural interpretation of decoherence. Each "world"
corresponds to a term in the wavefunction that no longer interferes
with others due to environmental entanglement. This framework aligns
with the unitary dynamics of quantum mechanics, avoiding the need for
collapse mechanisms.
While it is true that some explanations use terms like "observed," MWI
does not treat observation as a special ontological event. Instead,
observation is modeled as a unitary interaction between systems that
results in decoherence, creating branches of the wavefunction
corresponding to different outcomes. In this sense, "observation" in
MWI is a descriptive shorthand for the branching process and not an
additional mechanism requiring explanation. Your insistence that MWI
needs to explain "how and when worlds split" is strange to me; the
splitting is continuous and governed by the dynamics of decoherence.
Then does the split propagate from a microscopic event that starts the
split? How does it propagate? In a Bell experiment do all four
results occur and propagate?
Decoherence calculations, as I understand them, apply equally to MWI
and other interpretations, such as the neo-Copenhagen interpretation
(NCI). The question, then, seems here, in this thread, to be whether
one views the wavefunction as a real entity describing multiple
branches, as in MWI, or as an epistemic tool requiring collapse, as in
NCI. From my perspective, MWI avoids introducing additional ad hoc
elements, providing a simpler and more frugal, low cost explanation of
the same phenomena.
I'm well aware of MWI advocate's claims. But claims that it entails the
Born rule keep failing. And if you have to add an axiom to provide a
probabilistic interpretation of your multiple worlds, then it's just a
simple to say only one world exists with the associated probability.
If you find the connection between decoherence and MWI unsatisfactory,
it would be helpful to understand where you believe the explanatory
gap lies. Scholars like Zeh, Tegmark, and Wallace have elaborated on
these connections; and Schlosshauer’s reviews, in particular, provide
an agnostic mathematical context for decoherence —a context on which
there seems to be broad agreement in the field. And yet, I feel this
is all obvious to you. Your perspective on how these
studies/literature might then fall short of addressing your concerns
would clarify. What am I missing, besides a lifetime of more reading
and the beans to sustain the same?
You don't need to explain MWI to me. I have Schlosshauer's papers and
book as well as papers by Zeh, Zurek, Carroll, and others. What you are
missing is a skeptical curiosity. How is the Born rule realized? What
about Barandes Minimal Modal Interpretation, or Path Integrals, or
Invariant Set Theory...which seem to avoid multiple-worlds?
Brent
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