In both the Klein Gordon equation and the Dirac equation, when one
introduces the electromagnetic potential, A, one encounters a term:

(nambla A)psi

can one - at this point say, "I'll work in the Lorenz gauge and set
(nambla A) =0"? and solve the resulting (much simpler) equation?

My confusion - I think - comes from whether or not (nambla A) is an
operator or a factor on psi.
You may have a better idea than I on where my confusion lies.

Thanks for any help in educating me.

Thus spake Raphanus
In both the Klein Gordon equation and the Dirac equation, when one
introduces the electromagnetic potential, A, one encounters a term:

(nambla A)psi

can one - at this point say, "I'll work in the Lorenz gauge and set
(nambla A) =0"? and solve the resulting (much simpler) equation?

My confusion - I think - comes from whether or not (nambla A) is an
operator or a factor on psi.
You may have a better idea than I on where my confusion lies.

In the formulae to which I think you refer, (nambla A) is an operator,
and you cannot set it equal to 0. However, in some treatments the Gupta-
Bleuler gauge condition is used,

(nambla A)psi = 0.

This does then lead naturally to Lorenz gauge condition

nambla A = 0.

Regards

--
Charles Francis
moderator sci.physics.foundations.
charles (dot) e (dot) h (dot) francis (at) googlemail.com (remove spaces and
braces)

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