A Poincare lemma for sigma models of AKSZ type
Glenn Barnich, Maxim Grigoriev
TL;DR
The paper addresses the challenge of understanding local BRST cohomology for AKSZ-type sigma models. By exploiting the jet-space (variational bicomplex) framework, it proves that in coordinate neighborhoods the local BRST cohomology of such models is isomorphic to the $Q$-cohomology of the target space, and it extends this correspondence to the cohomology of functional multivectors. This reduces field-theoretic invariants, deformations, and symmetries to purely target-space data, providing a powerful tool for the inverse problem of the calculus of variations in general gauge systems. The results have concrete implications for classifying Lagrange and weak Poisson structures in AKSZ-type theories, with explicit examples illustrating the equivalence between spacetime and target-space cohomologies.
Abstract
For a sigma model of AKSZ-type, we show that the local BRST cohomology is isomorphic to the cohomology of the target space differential when restricted to coordinate neighborhoods both in the base and in the target. An analogous result is shown to hold for the cohomology in the space of functional multivectors. Applications of these latter cohomology classes in the context of the inverse problem of the calculus of variation for general gauge systems are also discussed.
