On Friday, February 7, 2020 at 5:07:41 AM UTC-6, Bruce wrote:
> On Fri, Feb 7, 2020 at 9:54 PM Lawrence Crowell <[email protected]
> <javascript:>> wrote:
>
>> On Thursday, February 6, 2020 at 10:59:27 PM UTC-6, Bruce wrote:
>>>
>>>
>>> This argument from Kent completely destroys Everett's attempt to derive
>>> the Born rule from his many-worlds approach to quantum mechanics. In fact,
>>> it totally undermines most attempts to derive the Born rule from any
>>> branching theory, and undermines attempts to justify ignoring branches on
>>> which the Born rule weights are disconfirmed. In the many-worlds case,
>>> recall, all observers are aware that other observers with other data must
>>> exist, but each is led to construct a spurious measure of importance that
>>> favours their own observations against the others', and this leads to an
>>> obvious absurdity. In the one-world case, observers treat what actually
>>> happened as important, and ignore what didn't happen: this doesn't lead to
>>> the same difficulty.
>>>
>>> Bruce
>>>
>>
>> This appears to argue that observers in a branch are limited in their
>> ability to take the results of their branch as a Bayesian prior. This
>> limitation occurs for the coin flip case where some combinations have a
>> high degree of structure. Say all heads or a repeated sequence of heads and
>> tails with some structure, or apparent structure. For large N though these
>> are a diminishing measure.
>>
>
> I don't think you have fully come to terms with Kent's argument. How do
> you determine the measure on the observed outcomes? The argument that such
> 'outlier' sequences are of small measure fails at the first hurdle, because
> all sequences have equal measure -- all are equally likely. In fact, all
> occur with unit probability in MWI.
>
> Bruce
>
This in reference to what is the distribution of outcomes, all one can do
is to use a Boltzmannian argument for e^{-E/kT} for 1/T a Euclideanized
time. If you want to get fancy you can use Bose-Einstein or Fermi-Dirac. So
this is somewhat model dependent, but not hopeless. For multiverse
connections to MWI the energy is the energy-mass gap from the inflationary
false vacuum to zero or maybe the observable vacuum based on the CC. This
is again somewhat phenom-dependent and a bit hand wavy, but not hopeless.
I don't think MWI is that much worse than other interpretations. In fact I
tend to see it as better than most.
LC
>
>
>
>> An observer might see their branch as having sufficient randomness to be
>> a Bayesian prior, but to derive a full theory these outlier branches with
>> the appearance of structure have to be eliminated. This is not a
>> devastating blow to MWI, but it is a limitation on its explanatory power.
>> Of course with statistical physics we have these logarithms and the rest
>> and such slop tends to be "washed out" for large enough sample space.
>>
>> No matter how hard we try it is tough to make this all epistemic, say
>> Bayesian etc, or ontological with frequentist statistics.
>>
>> LC
>>
>
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