G/H M-branes and AdSp+2 geometries

We discuss the class of BPS saturated M-branes that are in one-to-one correspondence with the Freund-Rubin compactifications of M-theory on either AdS(4) x G/H or AdS(7) x G/H, where G/H is any of the seven (or four) dimensional Einstein coset manifolds with Killing spinors classified long ago in the context of Kaluza-Klein supergravity. These G/H M-branes, whose existence was previously pointed out in the literature, are solitons that interpolate between flat space at infinity and the old Kaluza-Klein compactifications at the horizon. They preserve N/2 supersymmetries where N is the number of Killing spinors of the AdS x G/H vacuum, A crucial ingredient in our discussion is the identification of a solvable Lie algebra parametrization of the Lorentzian noncompact coset SO(2, p + 1)/SO(1, p + 1) corresponding to anti-de Sitter space AdS(p+2). The solvable coordinates are those naturally emerging from the near horizon limit of the G/H p-brane and correspond to the Bertotti-Robinson form of the anti-de Sitter metric. The pull-back of anti-de Sitter isometries on the p-brane world-volume contain, in particular, the recently found broken conformal transformations. (C) 1998 Elsevier Science B.V.