T-DUALITY AND HKT MANIFOLDS

We examine conformal rescaling and T-duality in the context of four-di mensional HKT geometries. The closure of the torsion forces the confor mal factor to satisfy a modified harmonic equation. Because of this eq uation the conformal factors form non-commutative groups acting on the HKT geometries. Using conformal rescalings and T-duality transformati ons we generate from flat space new families of HKT geometries with tr i-holomorphic Killing vectors. We also find ultraviolet-finite (4,0) s upersymmetric sigma models which are not conformally invariant. (C) 19 98 Elsevier Science B.V.