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Re: Subject Re: DRSSTC Tuning and Split Frequencies of Dual coupled system



Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Godfrey,

I have two advance engineering mathematics books with me. One talks about Lagrange's identity, interpolation formula, and reduction. The other talks about Lagrange's method of variation of parameters. So I guess I'm out of luck :-)) Oh well, I wasnt too serious about this anyway, just curious. Thankyou for the history.

Gerry R.


Original poster: "Godfrey Loudner" <ggreen@xxxxxxxx>

Hello Gerry

No, it is not variation of parameters. It has to do with the calculus of
variations and the formulation of physical laws as principles of least
action. Consult any book on advanced mechanics, such as "Classical
Mechanics, Goldstein" to study the Hamiltonian and Lagrangian
formulations of mechanics. There mention is made of such formulations
for electromagnetism. Most people would rather work within the confines
of Maxwell's formulation. However, for very daunting problems in
electromagnetism, variational principles seem to be the way to go, but
the hands of a master (not me) are required. For example, during the
development of early radar, a good theory was needed to account for the
properties of wave guides. In walks the theoretical physicist Julian
Schwinger, fresh from using variational techniques in the early quantum
field theories. He was a true master of exploiting variational
principles. He solved many of the wave guide problems using a powerful
variational approach. The engineers and other physicists were astonished
at the accuracy of the equations. There is a very unusual book
"Classical Electrodynamics, J. Schwinger", in which Schwinger derives
the classical theory from variational methods and some of his approach
to wave guides can be seen. The whole method of variations quickly boils
down to the question "just how good are you at finding Green's
functions, outside of the usual textbook problems?". Schwinger is the
person responsible for the greening of the quantum fields theories!

Godfrey Loudner
Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Jared,

Is this Lagrange's "method of variation of parameters". I can find so
little about it.

Gerry R.