The splitting of the de Rham cohomology of soft function algebras is multiplicative

Abstract

Let $A$ be a real soft function algebra. In arXiv:2208.11431 we have obtained a canonical splitting $\mathrm{H}^* (\Omega ^\bullet _{A|\mathrm{R}}) \cong \mathrm{H} ^* (X,\mathrm{R})\oplus \text{(something)}$ via the canonical maps $\Lambda_A:\mathrm{H} ^* (X,\mathrm{R})\to\mathrm{H} ^* (\Omega ^\bullet _{A|\mathrm{R}})$ and $\Psi_A:\mathrm{H} ^* (\Omega ^\bullet _{A|\mathrm{R}})\to\mathrm{H} ^* (X,\mathrm{R})$. In this paper we prove that these maps are multiplicative.