Topologies of maximally extended non-Hausdorff Misner Space (2402.09312v2)

Abstract: Misner (1967) space is a portion of 2-dimensional Minkowski spacetime, identified under a boost $\mathcal B$. It is well known that the maximal analytic extension of Misner space that is Hausdorff consists of one half of Minkowski spacetime, identified under $\mathcal B$; and Hawking and Ellis (1973) have shown that the maximal analytic extension that is non-Hausdorff is equal to the full Minkowski spacetime with the point $Q$ at the origin removed, identifed under $\mathcal B$. In this paper I show that, in fact, there is an infinite set of non-Hausdorff maximal analytic extensions, each with a different causal structure. The extension constructed by Hawking and Ellis is the simplest of these. Another extension is obtained by wrapping an infinite number of copies of Minkowski spacetime around the removed $Q$ as a helicoid or Riemann surface and then identifying events under the boost $\mathcal B$. The other extensions are obtained by wrapping some number $n$ of successive copies of Minkowski spacetime around the missing $Q$ as a helicoid, then identifying the end of the $n$'th copy with the beginning of the initial copy, and then identifying events under $\mathcal B$. I discuss the causal structure and covering spaces of each of these extensions.