Sigma-model for Generalized Composite p-branes

A multidimensional gravitational model containing several dilatonic scalar fields and antisymmetric forms is considered. The manifold is chosen in the form M = M_0 x M_1 x ... x M_n, where M_i are Einstein spaces (i > 0). The block-diagonal metric is chosen and all fields and scale factors of the metric are functions on M_0. For the forms composite (electro-magnetic) p-brane ansatz is adopted. The model is reduced to gravitating self-interacting sigma-model with certain constraints. In pure electric and magnetic cases the number of these constraints is m(m - 1)/2 where m is number of 1-dimensional manifolds among M_i. In the "electro-magnetic" case for dim M_0 = 1, 3 additional m constraints appear. A family of "Majumdar-Papapetrou type" solutions governed by a set of harmonic functions is obtained, when all factor-spaces M_k are Ricci-flat. These solutions are generalized to the case of non-Ricci-flat M_0 when also some additional "internal" Einstein spaces of non-zero curvature are added to M. As an example exact solutions for D = 11 supergravity and related 12-dimensional theory are presented.Comment: 33 pages, Latex. Some corrections and rearrangements are mad