Overconvergent subanalytic subsets in the framework of Berkovich spaces

Abstract

We study the class of overconvergent subanalytic subsets of a $k$-affinoid space $X$ when $k$ is a non-archimedean field. These are the images along the projection $X\times {\mathbb{B}}^n\to X$ of subsets defined with inequalities between functions of $X\times {\mathbb{B}}^n$ which are overconvergent in the variables of ${\mathbb{B}}^n$. In particular, we study the local nature, with respect to $X$, of overconvergent subanalytic subsets. We show that they behave well with respect to the Berkovich topology, but not to the $G$-topology. This gives counter-examples to previous results on the subject, and a way to correct them. Moreover, we study the case dim$(X)=2$, for which a simpler characterisation of overconvergent subanalytic subsets is proven.