Spin-Wave scattering in the effective Lagrangian perspective

Nonrelativistic systems exhibiting collective magnetic behavior are analyze d in the framework of effective Lagrangians. The method, formulating the dy namics in terms of Goldstone bosons, allows us to investigate the consequen ces of spontaneous symmetry breaking from a unified point of view. Low-ener gy theorems concerning spin-wave scattering in ferromagnets and antiferroma gnets are established, emphasizing the simplicity of actual calculations. T he present work includes approximate symmetries and discusses the modificat ion of the low-energy structure imposed by an external magnetic and an anis otropy field, respectively. Throughout the paper, analogies between condens ed matter physics and Lorentz-invariant theories are pointed out, demonstra ting the universal feature of the effective Lagrangian technique. [S0163-18 29(99)02725-3].