Grothendieck topologies with logarithmic modifications

Abstract

Many concepts in log geometry are invariant under log blow-ups. To formalize this invariance, we introduce the m-open, m-étale, m-smooth, m-fppf, and m-fpqc topologies for fs log schemes. These refine the standard topologies from scheme theory by treating abstract log modifications as covers. For example, the m-étale topology is a subtopology of full log étale topology, characterized by a stronger lifting property than for log étale maps. Along the way, we identify and correct an error in the definition of the full log étale topology. We also prove a global integralization theorem by logarithmic blow-ups and use it to describe the m-open topos as a limit over log blow-ups. Finally, we characterize the sheaves on the m-type sites and connect the m-open site to Kato's valuative space.