  We find all symmetric space solutions of eleven-dimensional supergravity
completing an earlier classification by Figueroa-O'Farrill. They come in two
types: AdS solutions and pp-wave solutions. We analyze the supersymmetry
conditions and show that out of the 99 AdS geometries the only supersymmetric
ones are the well known backgrounds arising as near-horizon limits of
(intersecting) M-branes and preserving 32, 16 or 8 supersymmetries. The general
form of the superisometry algebra for symmetric space backgrounds is also
derived.

High Energy Physics - Theory