Restoring Lorentz invariance in classical N=2 string Original Research Article

We study classical N=2 string within the framework of the N=4 topological formalism by Berkovits and Vafa. Special emphasis is put on the demonstration of a classical equivalence of the theories and the construction of an action for the N=4 topological string. The SO(2,2) Lorentz invariance missing in the conventional Brink–Schwarz action for the N=2 string is restored in the N=4 topological action.