Time Travel Paradoxes and Entangled Timelines (2303.07635v3)

Abstract: For time travel to be consistent with the known laws of physics, the resulting paradoxes must be resolved. It has been suggested that parallel timelines (a.k.a. multiple histories) may provide a resolution. However, so far, a concrete mechanism by which parallel timelines can be created has never been satisfactorily formulated. In this paper we propose such a mechanism within the framework of unmodified quantum mechanics, also known as the Everett or "many-worlds" interpretation. The timelines in our model are emergent, like the "worlds" of the Everett interpretation; they are created by quantum entanglement between the time machine and the environment. Therefore, we call them "entangled timelines" or E-CTCs. As the entanglement gradually spreads out to additional systems, the timelines spread out as well, providing a local and well-defined alternative to the naive "branching timelines" picture often presented in the literature. The E-CTC model is similar to Deutsch's familiar D-CTC model, but differs from it mainly by making the entanglement explicit, which allows us to create a clearer practical definition of the resulting parallel timelines.