Assume that λ λ is nonnegative. Then if the mass term is tachyonic, m 2 < 0 there is a spontaneous breaking of the gauge symmetry at low energies, a variant of the Higgs mechanism. On the other hand, if the squared mass is positive, m 2 > 0 the vacuum expectation of the field ϕ ϕ is zero. At the classical level the latter is true also if m 2 = 0 . However, as was shown by Sidney Coleman and Erick Weinberg, even if the renormalized mass is zero, spontaneous symmetry breaking still happens due to the radiative corrections (this introduces a mass scale into a classically conformal theory - the model has a conformal anomaly).