2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/176425We investigate spontaneous symmetry breaking within the linear sigma model with the SU(2)xU(1) internal symmetry at finite chemical potential, which was suggested as a model for kaon condensation in the CFL phase of dense quark matter. One-loop corrections to the scalar field effective potential as well as its propagator are calculated. Particular attention is paid to the type-II Goldstone boson that appears in the Bose--Einstein condensed phase. Furthermore, we show that the type-I Goldstone boson -- the superfluid phonon -- is allowed to decay due to the nonlinearity of its dispersion relation at high momentum, and determine its decay width.13 pages, REVTeX4, 37 eps figures; v2: substantial error in Sec. IV corrected, references added, other minor corrections; version to appear in Phys. Rev. DHigh Energy Physics - Phenomenologytext