A geometric degree formula for \(A\)-discriminants and Euler obstructions of toric varieties (Q616914)

The authors give combinatorial formulas for the degree of A-discriminant varieties introduced by Gelfand, Kapranov and Zelevinsky. Unlike the previously known formulas, the new ones apply to singular varieties and to the case when the dual variety is not a hypersurface. In fact the authors give a beautiful formula for the codimension of such a dual variety. The main new ingredient is the use of the Euler obstructions, which are determined in this paper for general toric varieties.