Causal uncertainty in quantum gravity

In a globally hyperbolic spacetime no closed timelike curves can exist. This implies that the concept of causality in General Relativity assumes the usual formulation, that is, effects must pertain to the future light cone of their respective causes. In turn, Quantum Field Theory asserts that causality is defined by the vanishing of field commutators for spacelike separations. However, this does not imply a direction for causal effects. Hidden in our conventions for quantization is a connection to the definition of an arrow of causality. If one allows mixed conventions within the same theory, then a causal uncertainty will naturally emerge. In some quantum-gravity theories, such as quadratic gravity, such a mixed causality condition occurs, which indicates that the concept of a light cone might be uncertain in quantum gravity. In this talk we will discuss some of the implications.