Superluminal chaos after a quantum quench

 I will present a formula to compute out-of-time-order correlators (OTOC) in generic asymptotically AdS spacetimes, based on the geodesic approximation to bulk propagators and the exchange of gravitational shock waves. In contrast to the standard method of Shenker and Stanford, this formula does not require to work in Fourier space and is therefore better suited when considering time-dependent holographic states. Applying this new method to the computation of OTOCs in quenched states dual to collapsing thin shells of matter (Vaidya spacetimes), we discover a transient superluminality in the butterfly velocity characterizing information scrambling in the system.