On spontaneous compactification of superstrings with torsion

Spontaneous compactification of the superstring field limit with nonzero antisymmetric tensor HMNP is considered. Existence of a class of solutions with internal spaces of constant negative curvature with zero cosmological constant is proved. Compactification on Ricci-flat spaces (in particular, on Kalabi-Yau spaces) is realized in the limit HMNP→0