On Friday, February 7, 2020 at 7:57:24 PM UTC-6, Bruce wrote:
>
> On Sat, Feb 8, 2020 at 12:28 PM Lawrence Crowell <goldenfield...@gmail.com 
> <javascript:>> wrote:
>
>> On Friday, February 7, 2020 at 7:10:54 PM UTC-6, Bruce wrote:
>>>
>>> On Sat, Feb 8, 2020 at 11:51 AM Lawrence Crowell <
>>> goldenfield...@gmail.com> wrote:
>>>
>>>> On Friday, February 7, 2020 at 6:16:45 PM UTC-6, Bruce wrote:
>>>>>
>>>>> On Sat, Feb 8, 2020 at 4:33 AM Stathis Papaioannou <stat...@gmail.com> 
>>>>> wrote:
>>>>>
>>>>>> On Fri, 7 Feb 2020 at 15:59, Bruce Kellett <bhke...@optusnet.com.au> 
>>>>>> 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.
>>>>>>>
>>>>>>
>>>> Carroll and Sebens worked a paper a year ago illustrating how MWI was 
>>>> consistent with Born rule. They did have to restrict paths or states that 
>>>> were too far removed from being a good Bayeisan prior, so it is a bit 
>>>> loose. However, it was not bad.
>>>>
>>>
>>> Not bad!!!! I suppose if you feel justified in just throwing away 
>>> anything that does not suit your favourite theory, then you can get away 
>>> with anything.  It is the fact that these 'worlds' that are far removed 
>>> from what one wants to see cannot just be "thrown away" that destroys MWI. 
>>> Given that the probability of particular outcomes no longer has meaning 
>>> when all outcomes necessarily occur, one cannot use any observed data to 
>>> justify any theory about the probabilities. All theories are just as good, 
>>> or just as bad. Consequently, assuming probabilities for particular 
>>> outcomes no longer makes any sense.
>>>
>>>
>> The set of amplitudes or paths thrown away is a small measure. The bounds 
>> are not entirely certain, but they are comparatively small.
>>
>
>
> The problem is to justify that the paths thrown away do, in fact, have 
> small measure. The proof given by Kent shows that, whatever result you 
> obtain, you can argue that contrary results have "small measure", and can 
> be thrown away. There is nothing that picks out one particular set of paths 
> as preferred in the many-worlds situation. One can only get that in a 
> stochastic one-world model.
>
> Bruce
>

No matter how hard we try statistics always has this element of 
subjectivity to it. Since entropy is S = -sum p log(p) the summation is a 
log and these errors tend not to be very large, As a corollary we have 
various definition of entropy and ways of computing it. This means that no 
matter how hard we try physics has this subjective aspect to it, and in a 
lot of ways Qubism has a few points along these lines.

LC

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