2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/165524Recent experiments [1],[2] which measured the spectrum of the Goldstone collective mode of coherently precessing state in 3He-B are discussed using the presentation of the coherent spin precession in terms of the Bose-Einstein condensation of magnons. The mass in the spectrum of the Goldstone boson -- phonon in the superfluid magnon liquid -- is induced by the symmetry breaking field, which is played by the RF magnetic field2 pages, JETP Letters style, no figures, version accepted in JETP LettersOther Condensed MatterStatistical MechanicsHigh Energy Physics - Phenomenologytext