Dynamical parity violation and the Chern-Simons term

We consider a three-dimensional model of two-component spinors with a quadrilinear self-interaction. In the $\frac{1}{N}$ expansion the model turns out to be renormalizable and a mass term is generated, violating parity. This allows for the generation of a Chern-Simons term if the spinor is coupled to an external gauge field. Parity violation and the associated induction of the topological term cease at a computable critical temperature.