Closed Timelike Curves and "Effective" Superluminal Travel with Naked Line Singularities

TL;DR

This paper explores how naked line singularities, called 'wires', can enable effective superluminal travel and create closed timelike curves without violating the Weak Energy Condition, challenging common assumptions about causality and energy conditions.

Contribution

It demonstrates that superluminal travel and CTCs can occur in spacetimes that preserve the Weak Energy Condition, using models with naked line singularities called 'wires'.

Findings

Wires can enable effective superluminal travel without WEC violation.

CTCs can form in spacetimes with moving wires, avoiding singularities.

WEC alone does not prevent superluminal travel or causality violations.

Abstract

We examine closed timelike curves (CTCs) and "effective" superluminal travel in a spacetime containing naked line singularities, which we call "wires". Each wire may be straight-line singularity or a ring singularity. The Weak Energy Condition (WEC) is preserved in all well-defined regions of the spacetime. (The singularities themselves are not well-defined, so the WEC is undefined there, but it is never explicitly violated.) Parallel to the wire, "effective" superluminal travel is possible, in that the wire may be used as a shortcut between distant regions of spacetime. Our purpose in presenting the superluminal aspects of the wire is to dispel the commonly held view that explicit WEC violation is necessary for effective superluminal travel, whereas in truth the strictures against superluminal travel are more complicated. We also demonstrate how the existence of such "wires" could create CTCs. We present a model spacetime which contains two wires which are free to move relative to each other. This spacetime is asymptotically flat: It becomes a Minkowski spacetime a finite distance away from each of the wires. The CTCs under investigation do not need to enter the wires' singularities, and can be confined to regions that are weak-field: This means that if these wires were physically possible, they would present causality problems even in nonsingular, energetically realistic regions of the spacetime. We conclude that the Weak Energy Condition alone is not sufficient to prevent superluminal travel in asymptotically flat spacetimes.