> On 11 Jan 2019, at 10:03, Philip Thrift <cloudver...@gmail.com> wrote:
> 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 
> <javascript:>> 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
> 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.


> - pt
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