Discrete and continuous exponential transforms of simple Lie groups of rank two

Abstract

We develop and describe continuous and discrete transforms of class functions on compact simple Lie group $G$ as their expansions into series of uncommon special functions, called here $\E$-functions in recognition of the fact that the functions generalize common exponential functions. The rank of $G$ is the number of variables in the $\E$-functions. A uniform discretization of the decomposition problem is described on lattices of any density and symmetry admissible for the Lie group $G$.