Time Evolution of Spin Waves

Department of Mathematics, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark(June, 1999)A rigorous derivation of macroscopic spin-wave equations is demonstrated. We introduce a macro-scopic mean-field limit and derive the so-called Landau-Lifshitz equations for spin waves. We firstdiscuss the ferromagnetic Heisenberg model at T = 0 and finally extend our analysis to general spinhamiltonians for the same class of ferromagnetic ground states.PACS numbers: 75.40.Gb, 67.57.Lm, 05.70.Ln