A remark on differentiability of Cauchy horizons

TL;DR

This paper provides a simpler proof that Cauchy horizons are differentiable at points where they have multiplicity one, building on prior work by Królak and Beem.

Contribution

It offers a more straightforward proof of the differentiability of Cauchy horizons at multiplicity one points.

Findings

Cauchy horizons are differentiable at points of multiplicity one

Simplified proof compared to previous work

Supports the understanding of horizon regularity

Abstract

In a recent paper Kr\'olak and Beem have shown differentiability of Cauchy horizons at all points of multiplicity one. In this note we give a simpler proof of this result.