Non-compact gaugings from higher dimensions

The N=8 supergravity theories in four (and five) dimensions with non-compact gauge groups are obtained from eleven- (and ten-) dimensional supergravities in backgrounds with non-compact internal spaces. The SO(p,q) gaugings are obtained by a consistent truncation of the higher-dimensional supergravity in a background that is a warped product of a four- (or five-) dimensional Einstein space with the hyperboloid Hp,q (i.e. the surface (z1)2+. . .+(zp)2-(zp+1)2-. . . -(zp+q)2=r2). For the non-semisimple CSO (p,q,r) gaugings Hp,q is replaced by the 'cylinder' Hp,q*Rr. These backgrounds are solutions of the higher-dimensional field equations precisely when the lower-dimensional supergravity has a SO(p)*SO(q) invariant vacuum solution. The mode analysis and massive spectra in these backgrounds are briefly considered.