# Modèles semi-factoriels et modèles de Néron

Research paper by Cédric Pépin

Indexed on: 26 Jan '12Published on: 26 Jan '12Published in: Mathematische Annalen

#### Abstract

Let S be the spectrum of a discrete valuation ring with function field K. Let X be a scheme over S. We will say that X is semi-factorial over S if any invertible sheaf on the generic fiber XK can be extended to an invertible sheaf on X. Here we show that any proper geometrically normal scheme over K admits a proper, flat, normal and semi-factorial model over S. We also construct some semi-factorial compactifications of regular S-schemes, such as Néron models of abelian varieties. The semi-factoriality property for a scheme X/S corresponds to the Néron property of its Picard functor. In particular, one can recover the Néron model of the Picard variety $${{\rm Pic}_{X_K/K,{\rm red}}^0}$$ of XK from the Picard functor PicX/S, as in the known case of curves. This provides some information on the relative algebraic equivalence on the S-scheme X.