Polynomial-Time Computation of the Degree of a Dominant Morphism in Characteristic Zero. I

Abstract

Consider a projective algebraic variety W that is an irreducible component of the set of all common zeros of a family of homogeneous polynomials of degrees less than d in n + 1 variables over the field of characteristic zero. We show how to compute the degree of a dominant rational morphism from W to W′. The morphism is given by homogeneous polynomials of degree d′.This algorithms is deterministic and polynomial in (dd′)n and the size of the input. Bibliography: 11 titles.