Quantum mechanics of periodic systems

The quantum description of a periodic system can be naturally embedded in a n auxiliary problem with an extended configuration space. Standard methods applied to the solution of the extended Schrodinger equation yield the resu lts usually obtained by the use of group theory or extensions of Floquet's theorem. This method is used to prove Bloch's theorem and to construct a mu ltimode Floquet method for the semiclassical theory of lasers interacting w ith atoms. (C) 1999 American Association of Physics Teachers.