2007/01/31 by Tomáš Brauner, Tomas Brauner · 2 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cold Atom Physics and Bose-Einstein Condensates #Quantum Chromodynamics and Particle Interactions #hep-ph
paper · pdf · doi:10.1103/physrevd.75.105014
published as Phys.Rev.D75:105014,2007 · v1: 16 pages, REVTeX4, 7 eps figures; v2: shortened (omitting details of calculations) on request from referee; version to appear in Phys. Rev. D
arxiv created 2007/05/14 · openalex publication_date 2007/05/18 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We investigate spontaneous symmetry breaking in Lorentz-noninvariant theories. Our general discussion includes relativistic systems at finite density as well as intrinsically nonrelativistic systems. The main result of the paper is a direct proof that nonzero density of a non-Abelian charge in the ground state implies the existence of a Goldstone boson with nonlinear (typically, quadratic) dispersion law. We show that the Goldstone boson dispersion relation may in general be extracted from the current transition amplitude and demonstrate on examples from recent literature, how the calculation of the dispersion relation is utilized by this method. After then, we use the general results to analyze the nonrelativistic degenerate Fermi gas of four fermion species. Because of its internal SU(4) symmetry, this system provides an analog to relativistic two-color quantum chromodynamics with two quark flavors. In the end, we extend our results to pseudo-Goldstone bosons of an explicitly broken symmetry.