Goldstone Bosons in the Appelquist-Terning ETC Model

Abstract

It is demonstrated that the extended technicolor model proposed recently by Appelquist and Terning has pair of potentially light $U(1)$ Goldstone bosons coupling to ordinary matter with strength $2m_f\over F_{\pi}$, where $m_f$ is the mass of the fermion and $F_{\pi} \approx 125\,\GeV$. These Goldstone bosons could get a mass if the spontaneously broken $U(1)$ symmetries are also explicitly broken, by physics beyond that specified in the model. An attempt to break these symmetries by embedding the model into a larger gauge group seems to be inadequate. The problem is because there are too many representations and there is a mismatch between the number of condensates and the number of gauge symmetries broken.