Weyl invariance, non-compact duality and conformal higher-derivative sigma models

We study a system of n Abelian vector fields coupled to n(n+1)/2 complex scalars parametrising the Hermitian symmetric space Sp(2n,R)/U(n). This model is Weyl invariant and possesses the maximal non-compact duality group Sp(2n,R). Although both symmetries are anomalous in the quantum theory, they should be respected by the logarithmic divergent term (the “induced action”) of the effective action obtained by integrating out the vector fields. We compute this induced action and demonstrate its Weyl and Sp(2n,R) invariance. The resulting conformal higher-derivative σ-model on Sp(2n,R)/U(n) is generalised to the cases where the fields take their values in (i) an arbitrary Kähler space; and (ii) an arbitrary Riemannian manifold. In both cases, the σ-model Lagrangian generates a Weyl anomaly satisfying the Wess–Zumino consistency condition.