Flow of dynamical causal structures with an application to correlations

Abstract: Causal models capture cause-effect relations both qualitatively - via the graphical causal structure - and quantitatively - via the model parameters. They offer a powerful framework for analyzing and constructing processes. Here, we introduce a tool - the flow of causal structures - to visualize and explore the dynamical aspect of classical-deterministic processes, arguably like those present in general relativity. The flow describes all possible ways in which the causal structure of a process can evolve. We also present an algorithm to construct its supergraph - the superflow - from the causal structure only. Consequently, the superflow of a given process may describe additional unrealizable evolutions of its causal structure. As an application, we show that if all leafs of a flow are trivial, then the corresponding process produces causal correlations only, i.e., correlations where past data influences future events only. This strengthens the result that processes, where the cycles in their causal structure are chordless, establish causal correlations only. We also discuss the main difficulties for the quantum generalization.