Abstract
A simple theorem is stated to expand the matrix element for a process concerning any number of photons or external electromagnetic fields into the independent gauge invariant terms. It turns out that the number of such terms is uniquely determined by the initial and final states of the process, regardless of the intermediate states and the type of interaction. We have, for example, 4, 14, and 10 independent gauge invariant terms for the production of spin and 1 mesons by photons and the Compton scattering, respectively. Some of the well-known absolute selection rules for meson decays can be also derived from this gauge invariant expansion theorem.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
