On Friday, January 11, 2019 at 4:16:13 AM UTC-6, Bruno Marchal wrote:
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> On 11 Jan 2019, at 10:03, Philip Thrift <cloud...@gmail.com <javascript:>> 
> wrote:
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> On Thursday, January 10, 2019 at 8:27:20 PM UTC-6, Bruce wrote:
>>
>> On Fri, Jan 11, 2019 at 12:18 PM Brent Meeker <meek...@verizon.net> 
>> wrote:
>>
>>> On 1/10/2019 4:21 PM, John Clark wrote:
>>>
>>> *So even Feynman knew that there was no theoretical value for the FSC, 
>>>> alpha.*
>>>>
>>>
>>> No,  he knew very well there was a theory that could come up with a 
>>> value because his own Feynman Diagrams could do it. But what he didn't know 
>>> and what nobody knows is why his theory came up with that particular pure 
>>> number when he never specifically stuck that number into the rules on how 
>>> the diagrams should operate. 
>>>
>>>
>>> The fine structure constant is e^2/hbar*c.  Those three values are 
>>> measured independent of any Feynman diagrams of quantum field theory.  The 
>>> calculation using Feynman diagrams is of the anamolous magnetic moment.   A 
>>> correction to the value of g that depend on relativistic effects (hence the 
>>> occurence of c in the denominator).  The anamolous magnetic moment can be 
>>> measure experimentally and using Feynman's diagrams and the measured values 
>>> of e, hbar, and c a value can be calculated that includes the relativistic 
>>> effects of quantum field theory. That's why the agreement with measurement 
>>> is significant.
>>>
>>
>> Right. The relation between fundamental physical constants, alpha = 
>> e^2/hbar*c, is the closest one gets to a "theoretical" value for the FSC. 
>> But that defines it in terms of other measured quantities. (Except that 
>> these days, c is a defined number, not a measured physical parameter.) The 
>> CODATA group use these theoretical relationships between constants, 
>> together with the best available measurements, to make simultaneous fits to 
>> all the constants and the data.That is where independent, "best values" for 
>> these parameters come from. It is using these in the Feynman diagram 
>> calculation of corrections to g-2 that gives the remarkable agreement 
>> between theory and experiment. The point, though, is that the value of the 
>> FSC used in calculating g-2 must be obtained independently of the g-2 
>> measurement or else it is not a test of QED.. Conversely, of course, the 
>> g-2 measurement can be use to estimate the FSC independently of other 
>> measurements.
>>
>> Bruce
>>
>>
>>> Brent
>>>
>>
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> As the Robert Geroch, James Hartle paper points out
>
> *    the issue of whether the existence of an algorithm to implement a 
> theory should be adopted*
> *    as a criterion for acceptable physical theories.* 
>
> if you want measurable constants to be computable, adopt a theory that 
> does so.
>
>
> Some constant might be intrinsically not computable. Normally, the 
> physical laws should at some point take into account the probability of 
> (self) halting, which would introduce a non computable constant in nature, 
> although it would be computable from the halting oracle. Mechanism prevents 
> the physical reality from being entirely computable. I suspect Planck 
> constant to be not computable, because if we extract QM from arithmetic, 
> the Planck constant might very well related to the mechanist substitution 
> level.
>
> We cannot choose a theory according to our metaphysical state, especially 
> in metaphysics. It has to be corroborated by the facts.
>
> Bruno
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Just as an example of another theory

*The Cellular Automaton Interpretation of Quantum Mechanics*
Gerard ’t Hooft
https://arxiv.org/pdf/1405.1548.pdf

What is computable in that theory?

Not saying this theory is a good one, but a theory is a theory is a theory.

- pt

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