Is the effective Lagrangian for quantum chromodynamics aσmodel?

A fully interacting effective chiral Lagrangian obeying the anomalous axial-baryon-current conservation law is constructed. This Lagrangian is a generalization of one implied by the 1/N approximation. In a certain sense, the old σ model is recovered. Our Lagrangian displays the dependence of amplitudes on the quantum-chromodynamic vacuum angle θ, gives soft η^' theorems, and hints at a possible complementarity between the instanton and 1/N approaches. We can rewrite our model in terms of a gauge-invariant gluon field.