Spectrum of Two-Magnon non-Heisenberg Ferromagnetic Model of Arbitrary Spin with Impurity

摘要

We consider a two-magnon system in the isotropic non-Heisenberg ferromagnetic model of an arbitrary spin s on a n-dimensional lattice Zⁿ. We establish that the essential spectrum of the system consists of the union of at most four intervals. We obtain lower and upper estimates for the number of three-particle bound states, i.e., for the number of points of discrete spectrum of the system.