מפגש קבוצת התיאוריה של אנרגיות גבוהות: The butterfly effect away from maximal chaos

Zoom: https://us02web.zoom.us/j/83037428657?pwd=Z3hubVhmbEtUYXNDajY1R2pTaWpHdz09

Abstract: 

A simple probe of chaos and operator growth in many-body quantum systems is the thermal out of time ordered (OTO) four point function. In a large class of local systems, the effects of chaos in this correlator build up exponentially fast inside a so called butterfly cone. I will discuss universal features of the spatiotemporal structure of this exponential growth in large N systems. In particular I will argue that there can be a smaller, “scramblon” cone inside the butterfly cone. Outside the scramblon cone, the growth of the OTO four point function is completely universal and saturates a chaos bound. Finally, I will discuss a connection between chaos and energy transport, called the pole skipping phenomenon, which is a subtle effect in the thermal energy density retarded two point function at a special point in the complex frequency and momentum planes. I will test this connection in the large q limit of an SYK chain, where I determine both the Lyapunov growth of the OTO correlator and the energy density two point function exactly as a function of the coupling, interpolating between weekly coupled and maximally chaotic behavior. 

Seminar Organizer: Andrea Guerrieri