Phase Structure of the Gauged Yukawa Model

抄録

We investigate the phase structure of the gauged Yukawa model possessing a global SU(2)_L × SU(2)_R symmetry and an unbroken(vector-like) gauge symmetry based on the ladder Schwinger-Dyson equation. We show that even when we tune the squared mass of the scalar boson in the Lagrangian to be positive, there occurs the dynamical chiral symmetry breaking due to fermion pair condensate(VEV of the composite scalar) triggered by the strong Yukawa coupling larger than a certain critical value. We find a "nontrivial ultraviolet fixed line" and "renormalized trajectories" in the three-dimensional coupling space of the Yukawa coupling, the gauge coupling and the "hopping parameter" of the elementary scalar field. Presence of the gauge coupling is crucial to existence of the fixed line.