Valuative compactifications of analytic varieties

Abstract

Let $X$ be an algebraic variety over $\mathbf{C}$. We define a canonical compactification $X^{\!\urcorner}$ of the complex analytic space $X(\mathbf{C})$ by adding a Berkovich space over a trivially valued field at the boundary. The construction is functorial with respect to proper morphisms and preserves many properties, such as normality, regularity, etc. We prove a partial GAGA theorem in this setting : there is an equivalence between the categories of coherent sheaves on $X$ and $X^{\!\urcorner}$, and it induces bijections on global sections. The results still hold if $\mathbf{C}$ is replaced by a complete non-trivially valued field $k$, and complex analytic spaces by Berkovich analytic spaces over $k$.