On 2/24/2025 3:07 AM, Quentin Anciaux wrote:
Bruce,

Your argument still assumes what it wants to prove. Yes, the 2^N sequences exist independently of the amplitudes, but the claim that they all contribute equally to probability remains an implicit assumption in your reasoning. The fact that the sequences themselves don’t depend on a and b does not mean that their statistical weights—how often an observer finds themselves in each sequence—are independent of amplitudes.
Which means you need some different, separate theory about how "observer distribution" is determined in a way that depends on the amplitudes.

Your core mistake is treating the observed sequences as primary while ignoring the fact that the number of observer instances experiencing each sequence is what matters. The amplitudes determine the measure of each branch, meaning the vast majority of observers end up in sequences that follow the Born rule.
Not necessarily a "vast majority".  For a short sequence, small N, there should be a lot of spread in the observed average.  Only for large N does the distribution become sharply peaked.  "Follow the Born rule" is a little ambiguous since it's probabilitistic. "Consistent with the Born rule" is better.

You are simply assuming that observer distribution is uniform across sequences, which contradicts the entire structure of quantum mechanics.
You mean it doesn't comport with the Born rule...and the Born rule is empirically confirmed...which is the whole point.  The Born rule must be invoked to assign numbers of observers, aka probabilities, to the 2^N sequences.

You keep insisting that different values of a and b still produce the same sequences. Yes, the sequences are the same in a mathematical sense, but that does not mean they are observed with equal frequency. This is like saying that rolling a biased die produces the same possible numbers as a fair die and then concluding that all outcomes are equally likely. The actual distribution of observed frequencies follows the amplitudes squared, as the Born rule predicts.

If you believe MWI contradicts the Born rule,
It doesn't contradict it unless you take it as the whole of the theory, without the Born rule.  If you don't include the Born rule, or an equivalent postulate, then you are left with nothing but counting the branches, which doesn't work for a=/=b.

Brent


publish a formal proof. Otherwise, repeating the same flawed argument does not make it more correct.

Quentin



Le lun. 24 févr. 2025, 11:49, Bruce Kellett <bhkellet...@gmail.com> a écrit :

    On Mon, Feb 24, 2025 at 5:31 PM Quentin Anciaux
    <allco...@gmail.com> wrote:

        Bruce,

        Your assertion is absurd. The existence of 2^N sequences is
        not in question—it's a direct prediction of MWI. The issue is
        whether all sequences contribute equally to probability, which
        they demonstrably do not, as experiments confirm the Born
        rule, not a uniform distribution.


    You are persisting with this idea that my argument is that all the
    2^N "sequences contribute equally to probability". But I have
    never made any such claim, and such an idea is completely beside
    the point. The first important point comes after I mention the 2^N
    binary sequences. I point out that these come from the binary
    state a|0> + b|1>, but the sequences themselves are independent of
    the amplitudes a and b. This means that if you repeat N trials
    with different amplitudes a and b, you will get exactly the same
    2^N sequences. The point of this is that the amplitudes themselves
    play no role in the formation of the experimentally observed
    binary sequences.

    You must remember that the sequences of UP and DOWN (or zero and
    one in my coding) are the data that any experimentalist measuring 
    the spin projections of N spin-half atoms will get. They are the
    data he/she will work with, and that data is independent of the
    amplitudes.

    The second point is that from that experimental data, the
    experimentalist can get an estimate of the probability of
    obtaining a zero. Say there are r zeros in someone's observed
    sequence. Then a good estimate of the probability of getting a
    zero will be p =  r/N. If one compares this with the Born rule
    prediction, which is |a|^2, then in the majority of cases the
    experimentalist will find the Born rule to be disconfirmed: his
    estimate p = r/N will not equal |a|^2. Since the same applies for
    any sequence in the set of 2^N:  the value of r for different
    experimentalists, will range from zero to one. But all have the
    same Born rule probability, |a|^2. This is what happens when the
    data from such an experiment is used for theory confirmation. MWI
    is not confirmed, whereas the single world model is confirmed on
    every occasion.

    The problem is made more acute if you consider that we can take
    completely different values for the amplitudes a and b, but we
    will get the same sequences, and the same set of values of p =
    r/N, even though the Born probabilities |a|^2 are wildly
    different. Of course, there is a value of r in the set of
    sequences that agrees with the Born probability, simply because
    the set of sequences covers all possibilities, including the set
    of zeros and ones that would be obtained by a single
    experimentalist in a single world scenario. In the single world,
    the Born rule is confirmed in every case, Though in the many-world
    case, the majority of experimentalists will find that the Born
    rule is violated.

    Bruce

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