representations. The trace of this self-intertwiner is called the nth Frobenius-Schur indicator. The original case of the Frobenius–Schur indicator is that for n = 2. The zeroth indicator is the dimension of the irreducible representation, the first indicator would be 1 for the trivial representation and zero for the other irreducible representations. It resembles the Casimir invariants for Lie algebra irreducible representations. In fact, since any representation of G can be thought of as a module for C[G] and vice versa, we can look at the center of C[G]. This is analogous to looking at the center of the universal enveloping algebra of a Lie algebra. It is simple to check that belongs to the center of C[G], which is simply the subspace of class functions on G. References G.Frobenius & I.Schur, Über die reellen Darstellungen der endlichen Gruppen (1906), Frobenius Gesammelte Abhandlungen vol.III, 354-377. Representation theory of groups Representation theory of Lie groups