More on the group algebra
We now go further into the structure of the group algebra G of a finite group G. As in Chapter 10, we write
a direct sum of irreducible G-modules Ui. In Theorem 10.5 we proved that every irreducible G-module U is isomorphic to one of the Ui. The question arises: how many of the Ui are isomorphic to U? There is an elegant ...