English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Causality is fundamental to science, but it appears in several differentforms. One is relativistic causality, which is tied to a space-time structureand forbids signalling outside the future. A second is an operational notion ofcausation that considers the flow of information between physical systems andinterventions on them. In [Vilasini and Colbeck, Phys. Rev. A. 106, 032204(2022)], we propose a framework for characterising when a causal model cancoexist with relativistic principles such as no superluminal signalling, whileallowing for cyclic and non-classical causal influences and the possibility ofcausation without signalling. In a theory without superluminal causation, bothsuperluminal signalling and causal loops are not possible in Minkowskispace-time. Here we demonstrate that if we only forbid superluminal signalling,superluminal causation remains possible and show the mathematical possibilityof causal loops that can be embedded in a Minkowski space-time without leadingto superluminal signalling. The existence of such loops in the given space-timecould in principle be operationally verified using interventions. Thisestablishes that the physical principle of no superluminal signalling is not byitself sufficient to rule out causal loops between Minkowski space-time events.Interestingly, the conditions required to rule out causal loops in a space-timedepend on the dimension. Whether such loops are possible in three spatialdimensions remains an important open question.

Impossibility of superluminal signalling in Minkowski space-time does not rule out causal loops