Operational Causality in Spacetime

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The no-signalling principle, preventing superluminal communication and the consequent logical paradoxes, is typically formulated within the information-theoretic framework in terms of admissible correlations in composite systems. In my talk, I will present its complementary incarnation associated with dynamics of single systems subject to invasive measurements. The dynamical no-signalling principle' applies to any theory with well defined rules of calculating detection statistics in spacetime. It thus offers a new framework, based on measure theory, for studying post-quantum'' theories in spacetime. I will show that, strikingly, the dynamical no-signalling' principle rules out some of the well know models of quantum wave dynamics.