Doubled Formalism, Complexification and Topological Sigma-Models

We study a generalization of the Alexandrov-Kontsevich-Schwarz-Zaboronsky (AKSZ) formulation of the A- and B-models which involves a doubling of coordinates, and can be understood as a complexification of the Poisson $\sigma$-model underlying these. In the flat space limit the construction contains models obtained by twisting an N=2 supersymmetric $\sigma$-model on Hull's doubled geometry. The curved space generalization involves a product of two diffeomorphic Calabi-Yau manifolds, and the $O(d,d)$ metric can be understood as a complexification of the CY metric. In addition, we consider solutions that can not be obtained by twisting the above $\sigma$-model. For these it is possible to interpolate between a model evaluated on holomorphic maps and one evaluated on constant maps by different choices of gauge fixing fermion. Finally, we discuss some intriguing similarities between aspects of the doubled formulation and topological M-theory, and a possible relation with results from the theory of Lie and Courant algebroids, where a doubled formulation plays a role in relating two- and three-dimensional topological theories.