Domain walls and theta dependence in QCD with an effective Lagrangian approach - art. no. 074023

We suggest an anomalous effective Lagrangian which reproduces the anomalous conformal and chiral Ward identities and topological charge quantization i n QCD. It is shown that the large N-c Di Vecchia-VenezianoWitten effective chiral Lagrangian is locally recovered from our results, along with 1/N-c c orrections, after integrating out the heavy "glueball" fields. All dimensio nful parameters in our scheme are fixed in terms of the quark and gluon con densates and quark masses. We argue that for a certain range of parameters, metastable vacua appear which are separated from the true vacuum of lowest energy by domain walls. The surface tension of the wall is estimated, and the dynamics of the wall is discussed. The U(1) problem and the physics of the pseudo Goldstone bosons at different theta angles are addressed within the effective Lagrangian approach. Implications for axion physics, heavy io n collisions and the development of the early Universe during the QCD epoch are discussed. [S0556-2821 (99)00109-5].