2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/149634Spontaneous symmetry breaking originats in quantum mechanical measurement of the relevant observable defining the physical situation, order parameter is the average of this observable. A modification is made on the random-phase postulate validating the ensemble description. Off-diagonal long-range order, macroscopic wavefunction and interference effects in many-particle systems present when there is a so-called nucleation of quantum state, which is proposed to be the origin of spontaneous gauge symmetry breaking, for which nonconservation of particle number N is not essential. The approach based on nonvanishing expectation of the field operator, $<\hatψ(\vec{r})>$, is only a coherent-state approximation in thermodynamic limit. When $N \to \infty$, this approach is equivalent, but $<\hatψ(\vec{r})>$ is not the macroscopic wavefunction.26 pages, Latex, a revised versionQuantum PhysicsCondensed Mattertext