On Friday, January 11, 2019 at 4:16:13 AM UTC-6, Bruno Marchal wrote: > > > On 11 Jan 2019, at 10:03, Philip Thrift <[email protected] <javascript:>> > 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 <[email protected]> >> 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. > > Bruno > > > > 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 -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
