Electroweak Symmetry Breaking via a Technicolor Nambu–Jona-Lasinio Model

We consider a theory of gauge fields and fermions which we argue gives rise to dynamics similar to that of the Nambu–Jona-Lasinio (NJL) model when a gauge coupling constant is appropriately fine-tuned. We discuss the application of this model to dynamical electroweak symmetry breaking by a top-quark condensate. In this model, custodial symmetry is violated solely by perturbatively weak interactions, and the top–bottom mass splitting is due to the enhanced sensitivity to custodial symmetry violation near the critical point. We also consider models in which electroweak symmetry is broken by new strongly-interacting fermions with NJL-like dynamics. We argue that these models require additional finetuning in order to keep corrections to the electroweak ρ-parameter acceptably small.