Electric/magnetic deformations of S³ and AdS₃, and geometric cosets

We analyze asymmetric marginal deformations of SU(2)_k and SL(2, ℝ)_k wzw models. These appear in heterotic string backgrounds with non-vanishing Neveu-Schwarz three-forms plus electric or magnetic fields, depending on whether the deformation is elliptic, hyperbolic or parabolic. Asymmetric deformations create new families of exact string vacua. The geometries which are generated in this way, deformed S³ or AdS ₃, include in particular geometric cosets such as S², AdS₂ or H₂. Hence, the latter are consistent, exact conformal sigma models, with electric or magnetic backgrounds. We discuss various geometric and symmetry properties of the deformations at hand as well as their spectra and partition functions, with special attention to the supersymmetric AdS₂ × S² background. We also comment on potential holographic applications.