Acausality in Gowdy spacetimes

TL;DR

This paper introduces a unified parametrization for Gowdy cosmological models with different topologies, revealing conditions under which acausal spacetimes and violations of cosmic censorship can occur.

Contribution

It provides a novel unified parametrization for Gowdy models that enables analysis of topologies and causality properties simultaneously.

Findings

Existence of a coordinate system with identical functional dependence for different topologies.

Identification of conditions leading to Cauchy horizons and acausality.

Only Kantowski-Sachs and Kerr-Gowdy metrics are acausal.

Abstract

We present a parametrization of $T^3$ and $S^1\times S^2$ Gowdy cosmological models which allows us to study both types of topologies simultaneously. We show that there exists a coordinate system in which the general solution of the linear polarized special case (with both topologies) has exactly the same functional dependence. This unified parametrization is used to investigate the existence of Cauchy horizons at the cosmological singularities, leading to a violation of the strong cosmic censorship conjecture. Our results indicate that the only acausal spacetimes are described by the Kantowski-Sachs and the Kerr-Gowdy metrics.