Dispersion and damping of acoustic magnons in a multicomponent collinear magnet at low temperatures

The frequencies and damping of the Goldstone modes are calculated in the spin-wave spectrum of a collinearly ordered spin system with arbitrary number of sublattices at low temperatures. The cases when the total spin of the system is equal to zero and nonzero are considered. The possibility is discussed of constructing a two-sublattice system equivalent to the original system in the sense that the frequencies and damping of the acoustic (Goldstone) magnons are equal.