Moduli spaces and brane solitons for M-theory compactifications on holonomy G2 manifolds

We investigate the local geometry on the moduli space of G(2) Structures that arises in compactifications of M-theory on holonomy G2 manifolds. In particular, we determine the homogeneity properties of couplings of the associated N = 1, D = 4 supergravity under the scaling of moduli space coordinates. We then find some brane solitons of N = 1, D = 4 supergravity that are associated with wrapping M-branes on cycles of the compact space. These include cosmic strings and domain walls that preserve 1/2 of supersymmetry of the four-dimensional theory, and nonsupersymmetric electrically and magnetically charged black holes. The geometry of some of the black holes is that of nonextreme M-brane configurations reduced to four dimensions on a seven torus. (C) 2001 Elsevier Science B.V. All rights reserved.