Normal projectivity of complete symmetric varieties

Abstract

Chiriv\`ı and Maffei \cite{CM II} have proved that the multiplication of sections of any two ample spherical line bundles on the wonderful symmetric variety $X=\bar{G/H}$ is surjective. We have proved two criterions that allows ourselves to reduce the same problem on a (smooth) complete symmetric variety to the corresponding problem on the complete toric variety (respectively to the open toric variety). We have also studied in details some family of complete symmetric varieties, in particular those of rank 2.