English

Higher Direct Images of the Structure Sheaf Over a Dedekind Domain

Algebraic Geometry 2026-02-17 v1

Abstract

We prove that for Noetherian, smooth, separated, integral, finite type schemes XX and YY over an excellent Dedekind domain RR, that are properly birational over RR, we have RifOXRigOYR^if_{*}\mathcal{O}_X \cong R^ig_{*} \mathcal{O}_Y and RifΩX/SdRigΩY/SdR^i f_{*}\Omega_{X/S}^{d} \cong R^ig_{*} \Omega_{Y/S}^d, where dd is the relative dimension of XX and YY over S=Spec(R)S= Spec(R), and ff and gg are the structure maps of XX and YY, respectively, as SS-schemes. As a corollary we obtain the vanishing of higher direct images of the structure sheaf for proper birational morphisms beteween such schemes. These results extend those obtained by Chatzistamatiou--R\"ulling over perfect fields of positive characteristic and we obtain them by extending their method of algebraic correspondences. We furthermore obtain as a corollary that if KK is a number field and OK\mathcal{O}_K its ring of integers and if XX is a smooth and proper KK-scheme with X\mathcal{X} and Y\mathcal{Y} two smooth proper models of XX over some dense open subscheme US=Spec(OK)U \subseteq S = Spec(\mathcal{O}_K), that if Hj(X,OX)H^j(\mathcal{X},\mathcal{O}_{\mathcal{X}}) is OS(U)\mathcal{O}_S(U)-torsion-free we have Hj(Xt,OXt)=Hj(Yt,OYt),H^j(\mathcal{X}_t,\mathcal{O}_{\mathcal{X}_t}) = H^j(\mathcal{Y}_t,\mathcal{O}_{\mathcal{Y}_t}), for all closed points tUt \in U.

Keywords

Cite

@article{arxiv.2602.13881,
  title  = {Higher Direct Images of the Structure Sheaf Over a Dedekind Domain},
  author = {Grétar Amazeen},
  journal= {arXiv preprint arXiv:2602.13881},
  year   = {2026}
}

Comments

56 pages. Comments welcome!