On an identity for the volume integral of the square of a vector field. Remark on a paper by A. M. Stewart

Comment on "On an identity for the volume integral of the square of a vector field"

Stewart has provided a position-space derivation of an identity for the volume integral of the square of a vector field that was quoted by Gubarev, Stodolsky and Zakharov. In this comment, I provide a momentum-space derivation of this result, generalized to the scalar product of two complex vector fields. This approach demonstrates the effective use of the Fourier transform technique in the context of vector analysis at a level suitable for undergraduate instruction.