Self-dual toric varieties

Abstract

We describe explicitly all multisets of weights whose defining projective toric varieties are self-dual. In addition, we describe a remarkable and unexpected combinatorial behaviour of the defining ideals of these varieties. The toric ideal of a self-dual projective variety is weakly robust, that means the Graver basis is the union of all minimal binomial generating sets. When, in addition, the self-dual projective variety has a non-pyramidal configuration, then the toric ideal is strongly robust, namely the Graver basis is a minimal generating set, therefore there is only one minimal binomial generating set which is also a reduced Gr\"obner basis with respect to every monomial order and thus, equals the universal Gr\"obner basis.