Abstract
One of the most fundamental problems in quantum many-body systems is the identification of a mean field in spontaneous symmetry breaking which is usually made in a heuristic manner. We propose a systematic method of finding a mean field based on the Lie algebra and the dynamical symmetry by introducing a class of symmetry-broken phases which we call -symmetry breaking. We show that for -symmetry breaking the quadratic part of an effective Lagrangian of Nambu-Goldstone modes can be block-diagonalized and that homotopy groups of topological excitations can be calculated systematically.
- Received 12 June 2015
- Revised 25 June 2016
DOI:https://doi.org/10.1103/PhysRevA.94.013613
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