On Thu, Aug 28, 2025 at 5:16 AM Brent Meeker <[email protected]> wrote:

> I think some specificity would help this debate.  Suppose N=6, so there
> are 64 different sequences in 64 different worlds.  The number of observers
> is irrelevants; we can suppose the results are recorded mechanically in
> each world.  Further suppose that a=b so there is no question of whether
> amplitudes are being respected.  Then in one of the worlds we have 011000.
> Per the Born rule its probability is 0.2344.  In MWI it is 1/64=0.0156.
> The difference arises because the observers applying the Born rule looks at
> it as an instance of 2 out of 6 successes.
>

The trouble with this is that you are treating this as an instance of
Bernoulli trials with probability p= 0.5. When every outcome occurs with
every trial we no longer have a Binomial distribution The Binomial
distribution assumes that you have x successes out of N trials. In the
Everettian case you have one success on every trial.

So your probability above for 2 successes applies to Bernoulli trials with
one as the 'success'. The thing is that the probability of getting a zero
is also 1/2, so we also have four successes out of six trials in your
example. The Binomial probability for this result is also 0.2344. Actually,
if we regard this experiment as a test of the Born rule, we have four zeros
in 6 trials, which gives an estimate of the probability as 4/6 = 0.667, or
as two ones in 6 trials which gives an estimate of the probability as 2/6 =
0.333, neither estimate is equivalent to |a|^2 = 0.5. The difference
becomes more pronounced as N increases. The problem with your analysis is
that you are assuming a binomial distribution. and we do not have any such
distribution.

Bruce

So why can't the MWI observer do the same calculation?  He certainly can.  *He
> can apply the Born rule.*  But when he does so, it can't be interpreted
> as a probability of his branch since such probabilities would add up to
> much more than 1.0 when summed over the 64 different worlds.  From the
> standpoint of statistics 011000 is the same as 001010 and their
> probabilities sum.  Their difference is just incidental, but they are
> different worlds in MWI and summing them makes no sense.
>
> Brent
>

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