Dynamical Lorentz symmetry breaking in a 4D massless four-fermion model

We study spontaneous Lorentz symmetry breaking for a four-dimensional massless four-fermion model. Our methodology is based on use of the rationalized propagator. We show that a bumblebee potential arises as a result of one-loop calculations and displays nontrivial minima. Also, we demonstrate that a phase transition restoring Lorentz invariance can occur at a finite temperature.