Local Constancy of Intersection Numbers

Abstract

We prove that, in certain situations, intersection numbers on formal schemes that come in profinite families vary locally constantly in the parameter. To this end, we define the product $S\times M$ of a profinite set $S$ with a locally noetherian formal scheme $M$ and study intersections thereon. Our application is to the Arithmetic Fundamental Lemma of W. Zhang where the result helps to remove a restriction in its recent proof, cf. arXiv:1909.02697.