On Thu, Apr 28, 2022 at 3:24 PM Brent Meeker <meekerbr...@gmail.com> wrote:

> On 4/26/2022 5:32 PM, smitra wrote:
>
> On 27-04-2022 01:37, Bruce Kellett wrote:
>
> Changing the weights of the components in the superposition does not
> change the conclusion of most observers that the actual probabilities
> are 0.5 for each result. This is simple mathematics, and I am amazed
> that even after all these years, and all the times I have spelled this
> out, you still seek to deny the obvious result. Your logical and
> mathematical skill are on a par with those of John Clark.
>
>
> It's indeed simple mathematics. You apply that to branch counting to
> arrive at the result of equal probabilities.
>
>
I have not used branch counting. Please stop accusing me of that.

> So, the conclusion has to be that one should not do branch counting. The
> question is then if this disproves the MWI. If by MWI we mean QM minus
> collapse then clearly not. Because in that case we use the Born rule to
> compute the probability of outcomes and assume that after a measurement we
> have different sectors for observers who have observed the different
> outcomes with the probabilities as given by the Born rule.
>
>
In which case the Born rule is just an additional arbitrary assumption: it
is not part of the Schrodinger equation. Your theory of QM minus collapse
is not well-defined. You simply take whatever you want from text-book
quantum mechanics, with no regard to the consistency of your model.

> You then want to argue against that by claiming that your argument applies
> generally and would not allow one to give different sectors unequal
> probabilities. But that's nonsense, because you make the hidden assumption
> of equal probabilities right from the start.
>
>
I simply assume the Schrodinger equation. Then, following Everett, we take
it to be deterministic, so that all branches occur on every trial. Since it
is deterministic, there is no concept of probability inherent in the
Schrodinger equation, and I do not assume any definition of probability. So
the branches occur as they occur, there is no assumption of equal
probability. It is just that the construction means that  all 2^N branches
occur on the same basis and necessarily count equally in the overall
branching picture.

There is nothing in QM that says that branches must count equally, and the
> lottery example I gave makes it clear that you can have branching with
> unequal probabilities in classical physics.
>
>
As I have said, there is no classical analogue of an interaction in which
all outcomes necessarily occur. So your lottery example is useless. There
is no concept of probability involved in any of this.

Bruce

>
> Yes, there's nothing in QM that says the branches must count equally.  But
> there's also nothing in the evolution of Schroedingers equation that they
> must count as *a^2* and *b^2*.  Of course IF they are probabilities then
> it follows from Gleason's theorem that they follow the Born rule.  But in
> that case you have reintroduced almost all the philosophical problems of
> the Copenhagen interpretation.  When exactly does this splitting occur?
> Can the split be into irrational numbers of branches?  A splitting is in
> some particular basis and not in other bases.  What determines the pointer
> basis?
>
> Brent
>

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