Gorenstein spherical Fano varieties

We obtain a combinatorial description of Gorenstein spherical Fano varieties in terms of certain polytopes, generalizing the combinatorial description of Gorenstein toric Fano varieties by reflexive polytopes and its extension to Gorenstein horospherical Fano varieties due to Pasquier. Using this description, we show that the rank of the Picard group of an arbitrary d-dimensional Q-factorial Gorenstein spherical Fano variety is bounded by 2d. This paper also contains an overview of the description of the natural representative of the anticanonical divisor class of a spherical variety due to Brion