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Problem: Spin Waves

     Determine the magnon (spin wave) dispersion curve in the one-dimensional ferromagnetic Heisenberg model,

equation2045

(where J;SPMgt;0 and tex2html_wrap_inline6327 is a spin operator), and in the Ising model, tex2html_wrap_inline6329 (where tex2html_wrap_inline6331 ). Site i is at position tex2html_wrap_inline6335 , where a is the lattice spacing.    

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Laszlo Mihaly
Thu Oct 31 13:23:11 EST 1996

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