2011/12/31 by Haruki Watanabe, Tomáš Brauner · 2 citations
Physics and Astronomy · #cond-mat.stat-mech #cond-mat.quant-gas #hep-ph #hep-th
paper · pdf · doi:10.1103/physrevd.85.085010
published as Phys.Rev.D85:085010,2012 · 14 pages, 4 pdf/jpg figures, REVTeX 4.1; v2: section IV expanded, new appendix and references added, numerous other minor modifications throughout the text
arxiv created 2012/01/30 · arxiv updated 2012/04/09
Unbroken continuous translational invariance is often taken as a basic assumption in discussions of spontaneous symmetry breaking (SSB), which singles out SSB of translational invariance itself as an exceptional case. We present a framework which allows us to treat translational invariance on the same footing as other symmetries. It is shown that existing theorems on SSB can be straightforwardly extended to this general case. As a concrete application, we analyze the Nambu-Goldstone modes in a (ferromagnetic) supersolid. We prove on the ground of the general theorems that the Bogoliubov mode stemming from a spontaneously broken internal U(1) symmetry and the longitudinal phonon due to a crystalline order are distinct physical modes.