AQM book: magnet gets magnons
As mentioned, Jeroen Danon and me are writting a book on Advanced Quantum Mechanics. We are expanding and elaborating exsisting lecture notes, making it more complete and interesting.
There was a lecture on magnets introducing many-body trial wave function and spontaneous symmetry breaking. Some time ago we got an idea to add magnons to this Chapter thereby introducing Goldstone boson idea, a bit of gauge techniques and random phase approximation. It looked like two-day job, but it took most of my working time for the last two weeks. This included refreshing master-level physics I happened to need, and analythical and numerical evaluation of magnon spectrum: something I always wanted to do but never dared to.
Despite a huge time loss, I enjoyed the activity, perhaps even more than the "real" research.
