In the Fermi-Hubbard model, it may lead to spin wave due to SO(3) symmetry breaking. I know how to derive the effective Lagrangian for the spin wave by integrating out the Fermi fields. However, how to derive a Lagrangian for the Fermi fields term, spin wave dynamic term and their interaction ? An example,
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This post imported from StackExchange Physics at 2015-02-04 06:01 (UTC), posted by SE-user Xinloong Han