Resultants and Discriminants for Bivariate Tensor-product Polynomials

Angelos Mantzaflaris (1) , Elias Tsigaridas (2)

1 RICAM - Johann Radon Institute for Computational and Applied Mathematics
2 PolSys - Polynomial Systems

Optimal resultant formulas have been systematically constructed mostly for unmixed polynomial systems, that is, systems of polynomials which all have the same support. However , such a condition is restrictive, since mixed systems of equations arise frequently in practical problems. We present a square, Koszul-type matrix expressing the resultant of arbitrary (mixed) bivariate tensor-product systems. The formula generalizes the classical Sylvester matrix of two univariate polynomials, since it expresses a map of degree one, that is, the entries of the matrix are simply coefficients of the input polynomials. Interestingly, the matrix expresses a primal-dual multiplication map, that is, the tensor product of a univariate multiplication map with a map expressing derivation in a dual space. Moreover, for tensor-product systems with more than two (affine) variables, we prove an impossibility result: no universal degree-one formulas are possible, unless the system is unmixed. We present applications of the new construction in the computation of discriminants and mixed discriminants as well as in solving systems of bivariate polynomials with tensor-product structure.

Mots clés: Koszul resultant matrix; tensor-product; polynomial system; solving; separation bounds; mixed discriminant

Domaines: Calcul formel [cs.SC]; Modélisation et simulation; Analyse numérique [math.NA]

Angelos Mantzaflaris, Elias Tsigaridas. Resultants and Discriminants for Bivariate Tensor-product Polynomials. ISSAC 2017 - International Symposium on Symbolic and Algebraic Computation, Mohab Safey El Din, Jul 2017, Kaiserslautern, Germany. pp.8, ⟨10.1145/3087604.3087646⟩. ⟨hal-01525560⟩