Chronology Protection Implementation in Analogue Gravity

TL;DR

This paper investigates the potential for analogue gravity systems to simulate spacetimes with Closed Timelike Curves (CTCs), revealing conditions under which such simulations are possible and proposing a chronology protection mechanism similar to Hawking's hypothesis.

Contribution

It demonstrates that analogue gravity can simulate CTCs without a chronological horizon, and introduces a universal behaviour near horizons, expanding the understanding of emergent gravity and CTC simulation.

Findings

Analogue systems can simulate CTCs if no chronological horizon exists.

A universal behaviour near horizon formation is identified.

Explicit geometries with CTCs, like warp-drive configurations, are constructed.

Abstract

Analogue gravity systems offer many insights into gravitational phenomena, both at the classical and at the semiclassical level. The existence of an underlying Minkowskian structure (or Galilean in the non-relativistic limit) in the laboratory has been argued to directly forbid the simulation of geometries with Closed Timelike Curves (CTCs) within analogue systems. We will show that this is not strictly the case. In principle, it is possible to simulate spacetimes with CTCs whenever this does not entail the presence of a chronological horizon separating regions with CTCs from regions that do not have CTCs. We find an Analogue-gravity Chronology protection mechanism very similar in spirit to Hawking's Chronology Protection hypothesis. We identify the universal behaviour of analogue systems near the formation of such horizons and discuss the further implications that this analysis has from an emergent gravity perspective. Furthermore, we build explicit geometries containing CTCs, for instance spacetimes constructed from two warp-drive configurations, that might be useful for future analysis, both from a theoretical and an experimental point of view.