Magnetic catalysis of P-parity breakdown in a massive Gross-Neveu model and high-Tc superconductivity

It is shown within the framework of the (2+1)-dimensional P-invariant massive Gross-Neveu theory that an external magnetic field induces a first-order phase transition that breaks the P parity. The use of the obtained results in the description of magnetic phase transitions in high-Tc superconductors is discussed.