Tangent fields on deformations of complex spaces

Properties of sheaves of graded Lie algebras associated with a flat mapping of complex spaces are established. In particular, for a minimal versal deformation the tangent algebra of a fiber defines a linearization of the algebra of liftable fields on the base, which in turn enables one to find the discriminant of the deformation and its modular subspace. A criterion is obtained for the nilpotency of the tangent algebra of the germ of a hypersurface with a unique singular point. It is proved that in the algebra of liftable fields on the base of a minimal versal deformation of such a germ there always exists a basis with symmetric coefficient matrix.