Symmetry and periodicity is discussed as it pertains to wave propagation, with particular emphasis on Floquet's theorem and Bloch's theorem. Floquet's theorem in three dimensions is applied to a circular waveguide with screw periodicity. The resulting dispersion characteristics of the uncoupled modes are compared to those of a normal circular waveguide.
W. N. Cain,
R. W. Grow,
"Symmetry And Periodicity For Millimeter Wave Devices", Proc. SPIE 1039, 13th Intl Conf on Infrared and Millimeter Waves, (18 November 1989); doi: 10.1117/12.978528; https://doi.org/10.1117/12.978528