Doubled space and extended supersymmetry

The doubled formulation of the worldsheet provides a description of string theory in which T-duality is promoted to a manifest symmetry. Here we extend this approach to N = (2, 2) superspace providing a doubled formulation for bi-Hermitian/generalised Kähler target spaces. The theory is described by a single function, a doubled-generalised Kähler potential, supplemented with a manifestly N = (2, 2) constraint. Several examples serve to illustrate this construction, including a discussion of the N = (2, 2) description of T-folds.