Scalar multiplets and asymptotic freedom

In a gauge theory of scalar mesons interacting with gauge vector particles, we show that scalar-meson four-point Green’s functions are free of infinities, provided that i) the scalar mesons do not couple to any fermions in the model and ii) there is no directλϕ ⁴-term in the Lagrangian. The proof relies on a «gauge approximation» technique which systematically exploits the information provided by Ward-Takahashi identities. For non-Abelian gauge theories, the significance of this result is that a large class of scalar multiplets which can induce spontaneous symmetry breaking do not affect the issue of asymptotic freedom. In order to exploit the information of Ward-Takahashi identities we use the «axial gauge», in which there are no fictitious scalar particles and the identities assume their naive form, withZ ₁ =Z ₂ for all matter and gauge fields.