A group theoretic operation which is useful in the study of complex atomic spectra. A plethysm takes a set of functions of a
given symmetry type and forms from them symmetrized products of a given degree and other symmetry type .
A plethysm
References
Littlewood, D. E. ``Polynomial Concomitants and Invariant Matrices.'' J. London Math. Soc. 11, 49-55, 1936.
Wybourne, B. G. ``The Plethysm of -Functions'' and ``Plethysm and Restricted Groups.'' Chs. 6-7 in
Symmetry Principles and Atomic Spectroscopy. New York: Wiley, pp. 49-68, 1970.