On 1/12/2019 2:51 AM, Philip Thrift wrote:


On Friday, January 11, 2019 at 7:19:06 PM UTC-6, Brent wrote:



    On 1/11/2019 1:57 PM, Philip Thrift wrote:


    On Friday, January 11, 2019 at 2:46:35 PM UTC-6, Brent wrote:



        On 1/11/2019 6:01 AM, John Clark wrote:
        On Thu, Jan 10, 2019 at 8:18 PM Brent Meeker
        <meek...@verizon.net> wrote:

            /> The fine structure constant is e^2/hbar*c.  Those
            three values are measured independent of any Feynman
            diagrams/


        Absolutely correct. So if you use Feynman diagrams to
        predict what some physical system is going to do, such as a
        physical system of 2 electrons being hit by a photon of
        light with a wavelength small enough to contain enough
        energy to prevent the electrons repulsion, then you'd better
        get a number very close to the Fine Structure Constant. If
        you don't then Feynman Diagrams aren't any good.

        They didn't use 12,672 Feynman Diagramsbecause they wanted
        to know what the Fine Structure Constantwas, they already
        knew what that number was to many decimal places from
        exparament, they used 12,672 Feynman Diagramsbecause they
        wanted to see if Feynman Diagrams worked. And it turned out
        they worked spectacularly well in that situation, and that
        gives scientists great confidence they can use Feynman
        Diagrams in other situations to calculate what other
        physical systems will do that involve the Electromagnetic Force.

        There's always an interplay between theory and experiment. 
        It's completely analogous to Maxwell's discovery that light
        is EM waves. There were already experimental values of the
        permittivity and permeability of the vacuum and there were
        values for the speed of light.  Maxwell showed that his
        theory of EM predicted waves and using the permittivity and
        permeability values the speed of the waves matched that of
        light.  Now the speed of light is a defined constant and so
        are the permittivity and permeability of the vacuum.  So the
        connecting of the three values by a theory allows their
        values to be defined.  In the case of the anomalous magnetic
        moment of the electron, hbar and c are already defined
        constants.  So quantum field theory (for which Feynman
        diagrams are just a calculational tool) linked them and e to g.

        Brent




    If Feynman Diagrams (tools) are sufficient (to match experimental
    data) then Quantum Field Theory can be thrown in the wastebasket.

    ?? Feynman Diagrams are just a mathematical trick for summing up
    terms to approximate the propagator of QFT.

    Brent



You just make Feynman Diagrams the fundamental elements of the theory, and propagators derived from them.

How many diagrams?  The propagator has a clear interpretation as connecting the field at x with the field at y.  Feynman showed that his diagrams provided a good mnemonic for the infinite number of terms that would sum to the propagator.  If you take the diagrams as fundamental you then need to specify how many.


Just like histories are made fundamental, and Hilbert Spaces are derived from them.

Hilbert spaces are infinite dimensional vector spaces.  So you have the same problem: How many histories?

Brent


            https://arxiv.org/abs/1002.0589

Theories do not come from Mount Olympus.

- pt
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