No Time Machine Construction in Open 2+1 Gravity with Timelike Total Energy Momentum

TL;DR

This paper proves that in 2+1 dimensional gravity, spacetimes with timelike sources and total energy cannot form stable Cauchy horizons, implying that constructing a time machine in such settings is impossible.

Contribution

It provides a proof of a version of Kabat's conjecture, showing that open 2+1 gravity spacetimes cannot host stable time machines with timelike total energy.

Findings

No stable Cauchy horizons in open 2+1 gravity with timelike sources.

Time machine construction is impossible in these spacetimes.

Supports the conjecture that certain spacetime configurations cannot produce time machines.

Abstract

It is shown that in 2+1 dimensional gravity an open spacetime with timelike sources and total energy momentum cannot have a stable compactly generated Cauchy horizon. This constitutes a proof of a version of Kabat's conjecture and shows, in particular, that not only a Gott pair cannot be formed from processes such as the decay of a single cosmic string as has been shown by Carroll et al., but that, in a precise sense, a time machine cannot be constructed at all.