Effective de Rham cohomology — The general case

Abstract

Grothendieck has proved that each class in the de Rham cohomology of a smooth complex affine variety can be represented by a differential form with polynomial coefficients. We prove a single exponential bound on the degrees of these polynomials for varieties of arbitrary dimension. More precisely, we show that the [Formula: see text]th de Rham cohomology of a smooth affine variety of dimension [Formula: see text] and degree [Formula: see text] can be represented by differential forms of degree [Formula: see text]. This result is relevant for the algorithmic computation of the cohomology, but is also motivated by questions in the theory of ordinary differential equations related to the infinitesimal Hilbert 16th problem.