Violation of Parity and Flavor Symmetries in a Nambu–Jona-Lasinio Model

We study a lattice Nambu–Jona-Lasinio model with certain continuous chiral and two-flavor symmetries. For the Hamiltonian of the model, we construct a ground state which breaks the parity and flavor symmetries. In our argument, the chiral symmetry plays a crucial role in proving the violation of the parity and flavor symmetries, although the model does not contain the so-called Wilson term.