Black hole shadow and chaos bound violation in f(T) teleparallel gravity

We show that the so-called chaos bound, proposed by Maldacena, Shenker & Stanford, can be violated in f(T) teleparallel gravity. In particular, it is possible to select a new gravitational Lyapunov parameter, controlling chaotization of circular trajectories, black hole photo-sphere, exceed Stanford thermal bound. This feature alters standard quasi-normal modes and ringdown phase after merging with intriguing implications for future wave detections shadow measurements. It general characteristic several theories beyond General Relativity.