On 11-05-2022 07:25, Brent Meeker wrote:
On 5/10/2022 8:11 PM, smitra wrote:
On 09-05-2022 00:34, Bruce Kellett wrote:
On Mon, May 9, 2022 at 6:52 AM smitra <smi...@zonnet.nl> wrote:

On 08-05-2022 06:04, Bruce Kellett wrote:
On Sun, May 8, 2022 at 11:21 AM smitra <smi...@zonnet.nl> wrote:

The issues with branches etc. are likely just artifacts with
hidden assumptions about branches. At the end of the day there
a finite number of states an observer can be in. If an observer
modeled as an algorithm, take e.g. Star Trek's Mr. Data then it's
that there are only a finite number of bitstrings that can
correspond to
the set of all possible things Mr. Data can be aware of.

Everett is supposed to be QM without observers. So the number of
things that Mr Data can possibly be aware of is irrelevant.
to the SE, all branches are equivalent. All else flows from this
there are no further "hidden assumptions about branches".

Yes, but I'm not a big fan of "sticking to scripture". What matters
me is that collapse is inconsistent with the SE, therefore we should

consider QM without collapse and see how to best to move forward on

That still treats the SE as indubitally true. No theory in physics is
'indubitably true'.

The Everett program is to say that the SE is all that there is -- it
explains everything. That is clearly false (no Born rule in the SE),
so it might be wise to doubt the universal application of the SE.

There is no good reason to doubt the SE without any experimental hints that it breaks down, or any good theoretical reasons why it is likely to break down in some regime.

Well, there's a big fat hint that it breaks down FAPP in every
measurement, in every bit of physics that appears classical and
irreversible.  So it has a burden to explain this appearance. 

It does not have the burden to explain this fully. Lacking a good explanation, one has to go through all reasonable explanations based on what is known. A good example is what John Clark also mentioned about time reversibility. Boltzmann presented an incomplete argument on how the tension between the Second law and microscopic time reversibility could be resolved. And while the precise rigorous argument was not satisfactorily settled until quite recently, it was good enough for physicists to move on and accept that the laws of physics are time reversible.

This is because it was implausible to have time reversibility at the micro-level and not at a higher level, given that what happens at the macro-level is fully determined by what happens at the micro-level. It would require new experimental results to cast doubt on reversibility, so the burden of proof is on anyone proposing such a hypothesis.

The case of unitary time evolution is similar. There are no experimental results that demonstrate that this is violated. While we do have effective collapse at the macro-scale, this is what one would expect due to decoherence.

I see
some progress in this direction in decoherence and Zurek's quantum
Darwinism.  But it still ends in hand waving,

Physics would not be possible without lots of hand waving.

"Since the SE applies to
everything the wave-function must be real and every component of it
must exist." 
Which begs the question, "Does it apply to everything?" 
It doesn't apply to spacetime and gravity.

It does apply to spacetime, at least there is no problem with assuming that it does. See e.g. here for some details:


In particular Section 4.1. "How to Make Computations" on page 23 and further

  And it might just be an
effective approximation as in QBism.

That could be, but as things stand now, there is no evidence for that.



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