M Moser, A Prets and W L Spitzer
Time Evolution of Spin Waves 
(20K, Rev-Tex)

ABSTRACT.  A rigorous derivation of macroscopic spin-wave equations is 
demonstrated. We introduce a macroscopic mean-field limit and derive 
the so-called Landau-Lifshitz equations for spin waves. We first discuss 
the ferromagnetic Heisenberg model at $T=0$ and finally extend our 
analysis to general spin hamiltonians for the same class of 
ferromagnetic ground states.