Non-Critical Covariant Superstrings

We construct a covariant description of non-critical superstrings in even dimensions. We construct explicitly supersymmetric hybrid type variables in a linear dilaton background, and study an underlying N = 2 twisted superconformal algebra structure. We find similarities between non-critical superstrings in 2n + 2 dimensions and critical superstrings compactified on CY4−n manifolds. We study the spectrum of the non-critical strings, and in particular the Ramond-Ramond massless fields. We use the supersymmetric variables to construct the non-critical superstrings σ-model action in curved target space backgrounds with coupling to the Ramond-Ramond fields. We consider as an example non-critical type IIA strings on AdS2 background with Ramond-Ramond 2-form flux.