GEOMETRICAL DESCRIPTION OF SMOOTH PROJECTIVE SYMMETRIC VARIETIES WITH PICARD NUMBER ONE

In [R2] we have classified the smooth projective symmetric G-varieties with Picard number one (and G semisimple). In this paper we give a geometrical description of such varieties. In particular, we determine their automorphism group. When this group acts nontransitively on X, we describe a G-equivariant embedding of the variety X in a homogeneous variety (with respect to a larger group). We show that these varieties are all related to the exceptional groups.