Faster than light motion does not imply time travel

TL;DR

This paper demonstrates a (3+1)-dimensional Minkowski spacetime model where faster-than-light motion exists without leading to time travel, challenging the common assumption that FTL implies causality violations.

Contribution

It provides a novel spacetime model showing FTL motion does not necessarily result in time travel, countering previous causality violation arguments.

Findings

FTL motion can exist without enabling time travel.

The model preserves the Principle of Relativity.

Causality violations are not an inevitable consequence of FTL.

Abstract

Seeing the many examples in the literature of causality violations based on faster-than- light (FTL) signals one naturally thinks that FTL motion leads inevitably to the possibility of time travel. We show that this logical inference is invalid by demonstrating a model, based on (3+1)-dimensional Minkowski spacetime, in which FTL motion is permitted (in every direction without any limitation on speed) yet which does not admit time travel. Moreover, the Principle of Relativity is true in this model in the sense that all observers are equivalent. In short, FTL motion does not imply time travel after all.