Causal loops: Logically consistent correlations, time travel, and computation

Abstract

Causal loops are loops in cause-effect relations, where, say for two events A, B, the event A is a cause of B and, vice versa, B is a cause of A. Such loops are traditionally ruled out due to potential logical problems, e. g., where an effect suppresses its own cause. Motivated by our current physical theories, we show that not only causal loops exist that are logically consistent, but that these loops are computationally tame and help to further investigate on the theoretical foundations of time travel. Causal loops do not necessarily pose problems from a logics, computer-science, and physics point of view. This opens their potential applicability in various fields from philosophy of language to computer science and physics.