The c-completion of Lorentzian metric spaces

Abstract

Abstract Inspired by some Lorentzian versions of the notion of metric and length space introduced by Kunzinger and Sämman (2018 Ann. Glob. Anal. Geom. 54 399–447), and more recently, by Müller (2022 arXiv:2205.01617), and Minguzzi and Suhr (2023 arXiv:2209.14384), we revisit the notion of Lorentzian metric space in order to later construct the c-completion of these general objects. We not only prove that this construction is feasible in great generality for these objects, including spacetimes of low regularity, but also endow the c-completion with a structure of Lorentzian metric space by itself. We also prove that the c-completion constitutes a well-suited extension of the original space, which really completes it in a precise sense and becomes sensible to certain causal properties of that space.