[FOM] Question about theoretical physics
Arnold Neumaier
Arnold.Neumaier at univie.ac.at
Wed Mar 6 03:00:11 EST 2013
On 03/02/2013 07:57 PM, Joe Shipman wrote:
> Can Professor Neumaier, or any other theoretical physicist, provide a link the following much simpler pieces of documentation?
>
> 1) a method for enumerating Feynman diagrams relevant to the calculation of the magnetic moment of the electron
This is not how it is done. The actual high order computations involve
an expansion in powers of both alpha and 1/c^2, and the choice of the
temrs evaluated is based on heuristics which ones are likely to
influence the result. The actual method used is NRQED, not the standard
Feynman series expansion. Figuring out what precicesly has been done or
needs to be done to replicate the results is itself a research project
that only those are interested to do who actually want to do the
checking (usually because they have an alternative in mind that might
work better).
> 2) a high-level description of the process by which the value of a Feynman integral for *one specific nontrivial Feynman diagram* is numerically approximated
The contribution of a single Feynman integral is infinite, except for
the lowest order (zero loop) tree level disarams. Finite values arise
form linear combinations of such contributions that have a definite
finite value in the renormalization limit.
The closest approximation to what you want is in the work by Kreiner,
but this is itself quite abstract (involving Hopf algebras) and
acccessible only to a small part of theretical physicists.
Arnold Neumaier
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