On 3/7/2020 4:05 AM, Lawrence Crowell wrote:
On Friday, March 6, 2020 at 7:51:10 PM UTC-6, Brent wrote:
On 3/6/2020 3:55 PM, Bruce Kellett wrote:
On Sat, Mar 7, 2020 at 10:17 AM John Clark <[email protected]
<javascript:>> wrote:
This video just went online, I thought it was excellent:
Parallel Worlds Probably Exist. Here’s Why
<https://www.youtube.com/watch?v=kTXTPe3wahc>
John K Clark
Impressive graphics, but the same old....same old....
Bruce
You might find this interview of Sean Carroll more interesting.
He's aware of the problems with MWI and is fairly candid about it
even though he likes it. Start at 54:00 to skip all the
explanation of QM. https://www.youtube.com/watch?v=XjDiOu5__oA
<https://www.youtube.com/watch?v=XjDiOu5__oA>
Brent
The question on whether QM has an infinite or finite Hilbert space can
be addressed with the existence of event horizons. The cosmological
event horizon puts a limit. Consider a Planck scale quantum state that
has been redshifted to the cosmological horizon scale. This is a ratio
of around 10^{60} and from the FLRW this leads to a distance of around
1800 billion light years. Since this defines a finite region this
means the Hilbert space accessible to any observer is finite, even if
enormously large. Even if the global Hilbert space is infinite,
observers are fundamentally local and the amount of quantum
information accessible is finite. To take this further, with
inflationary cosmology the cosmological event horizon on the high
energy vacuum was only 10^2 or 10^3 Planck units of radius the large
number of quantum states that appear accessible on the low energy
physical vacuum are an enormous redundancy.
At around 1:14 Carroll gets to brass-tacks on this issue with the
horn. The idea in MWI is then "everything happens that can happen,"
which some people find difficult. In effect even though there is a
probability weight with each possible branch, an observer that
witnesses a highly improbable quantum event has this sense they are on
a split branch and have no post collapse information about a prior
probability. MWI has the concept of a cosmic wave function, but this
sense of there being only two outcomes reflects a lack of
counterfactual definite reasoning tied to objective probabilities. As
a result these branches occur in a certain nonlocal sense.
Is this at all demonstrable? No, counterfactual definite reasoning and
the existence of a global wave are not demonstrable. There are forms
of horizons, in general a form of epistemic horizon, which are a
generalization of the inaccessibility of information in QM and with
general relativity and event horizons. So whether there is or is not a
global cosmological wave function is a metaphysical choice of an
analyst. Generally ψ-ontological interpretations have a global cosmic
wave function, but a subset of those with a hidden variable
interpretation also have counterfactualism.
As Carroll points out there are four major types of interpretations,
MWI and deBroglie-Bohm, both ψ-ontic but with and without
counterfactualism, and Qubism and dynamic collapse that
are ψ-epistemic. Qubism has some advantages, but it leads to odd ideas
that are almost solipsism. Dynamic collapse and related idea of
stochastic QM have wave functions just spontaneously collapse and the
more entangled the system is the more frequent this will happen.
Isn't the Transactional Interpretation a kind of dynamic collapse, in
which a possibility is actualized by the absorbtion of energy or
information?
Brent
I have certain issues there with how to treat coherent states such as
with lasers or with condensates of states. In general one can pick and
choose, and these are available for those who want to think of certain
problems in a certain framework. I think frankly that QM decoherence,
and by extension a measurement, amounts to a sort of Gödel numbering
of quantum bits by quantum bits. I see all of these interpretations of
QM then as a sort of incompleteness or inconsistency that results by
trying to impose a certain question or proposition on QM that is not
decidable.
LC
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