Singular Vectors of the Topological Conformal Algebra

A general construction is found for `topological' singular vectors of the twisted N=2 superconformal algebra. It demonstrates many parallels with the known construction for sl(2) singular vectors due to Malikov--Feigin--Fuchs, but is formulated independently of the latter. The two constructions taken together provide an isomorphism between topological and sl(2)- singular vectors. The general formula for topological singular vectors can be reformulated as a chain of direct recursion relations that allow one to derive a given singular vector |S(r,s)> from the lower ones |S(r,s'<s)>. We also introduce generalized Verma modules over the twisted N=2 algebra and show that they provide a natural setup for the new construction for topological singular vectors.