Electromagnetic eigenfunctions

Two states /a and /b that are eigenfunctions of a Hamiltonian Hq in the absence of some external perturbation (e.g., electromagnetic field or static electric field or potential due to surrounding ligands) can be "coupled" by the perturbation V only if the symmetries of V and of the two wavefunctions obey a so-called selection rule. In particular, only if the coupling integral (see Appendix D which deals with time independent perturbation theory)... 

It is assumed that the eigenfunction (x) operated on by these infinitesimal field generators is such that the same relation (803) holds between eigenvalues of the field. In order for this to be true, the eigenfunction must be the de Broglie wave function, specifically, the phase of the classical electromagnetic field. On the 0(3) level, this is a line integral, as we have seen. 

The second complication is that the equation, as traditionally interpreted, only handles point particles, but produces eigenfunction solutions of more complex geometrical structure. By analogy with electromagnetic theory the square of the amplitude function could be interpreted as matter intensity, but this is at variance with the point-particle assumption. The standard way out is to assume that ip2 represents a probability density rather than intensity. Historical records show that this interpretation of particle density was introduced to serve as a compromise between the rival matrix and differential operator theories of quantum observables, although eigenvalue equations, formulated in either matrix or differential formalism are known to be mathematically equivalent. 

Let us, for its derivation, consider a Hamiltonian H P) with eigenfunctions o(- )) and eigenvalues Eo P) that all depend on the general electromagnetic field P with components Pa-.-... 

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