Embeddings and intersections of adelic groups

Abstract

We prove embeddings of adelic groups on an excellent scheme of special type and a flat quasicoherent sheaf on it. For a normal excellent scheme of special type we establish the equality ${\mathbb{A}}_I(X,\mathcal{F})\cap {\mathbb{A}}_J(X,\mathcal{F})={\mathbb{A}}_{I\setminus 0}(X,\mathcal{F})$ in the case $I\cap J=I\setminus 0$. We show that the limit of restrictions of global sections of a locally free sheaf on a Cohen-Macaulay projective scheme to power thickenings of integral subschemes equals the group of global sections of this sheaf. Using this result, we deduce a theorem on intersections of adelic groups for normal projective surfaces. We also compute cohomology groups of a curtailed adelic complex and, as a consequence, show that on a three-dimensional regular projective variety over a countable field the intersection ${\mathbb{A}}_I(X,\mathcal{F})\cap {\mathbb{A}}_J(X,\mathcal{F})$ equals ${\mathbb{A}}_{I\cap J}(X,\mathcal{F})$ for any $I,J\subset \{0,1,2,3\}$ and any locally free sheaf $\mathcal{F}$ on $X$.

42 pages. v3: Edited the proof of theorem 4.1.1, other changes. v2: Added remarks 1.1.18 and 1.2.8, added a reference, edited abstract, edited introduction, other changes