We show that the field of a charge at rest can always be considered as a superposition of evanescent waves of zero frequency. By proposing a two-dimensional Fourier expansion (instead of the three-dimensional one imposed by Landau and Lifshitz), we obtain a development of the Coulomb field in <i>plane evanescent waves of zero frequency</i>. This development is not valid in an arbitrary plane that contains the charge. By proposing a one-dimensional Fourier expansion we obtain a development in <i>cylindrical evanescent waves of zero frequency</i>. This last development is not valid in an arbitrary axis that contains the charge. These expansions enable us to analyze electrostatic boundary-value problems in a novel way.
© 1980 Optical Society of AmericaPDF Article