Weekly Papers on Quantum Foundations (9)

Authors: Ämin BaumelerFabio CostaTimothy C. RalphStefan WolfMagdalena Zych

General relativity predicts the existence of closed time-like curves, along which a material object could travel back in time and interact with its past self. The natural question is whether this possibility leads to inconsistencies: Could the object interact in such a way to prevent its own time travel? If this is the case, self-consistency should forbid certain initial conditions from ever happening, a possibility at odds with the local nature of dynamical laws. Here we consider the most general deterministic dynamics connecting classical degrees of freedom defined on a set of bounded space-time regions, requiring that it is compatible with arbitrary operations performed in the local regions. We find that any such dynamics can be realised through reversible interactions. We further find that consistency with local operations is compatible with non-trivial time travel: Three parties can interact in such a way to be all both in the future and in the past of each other, while being free to perform arbitrary local operations. We briefly discuss the quantum extension of the formalism.

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