A remark on the Mayer-Vietoris double complex for singular cohomology

Abstract

Given an open cover of a paracompact topological space X, there are two natural ways to construct a map from the cohomology of the nerve of the cover to the cohomology of X. One of them is based on a partition of unity, and is more topological in nature, while the other one relies on the Mayer-Vietoris double complex, and has a more algebraic flavour. In this paper we prove that these two maps coincide, thus answering a question posed by N. V. Ivanov.