We study the out-of-time-order correlation function (OTOC) in a
lattice extension of the Sachdev-Ye-Kitaev (SYK) model with quadratic
perturbations. The results obtained are valid for arbitrary time
scales, both shorter and longer than the Ehrenfest time. We
demonstrate that the region of well-developed chaos is separated from
the weakly chaotic region by the “front region”, which moves
ballistically across the lattice. The front velocity is calculated for
various system’s parameters, for the first time for SYK-like models.

*Aleksey Lunkin, Landau Institute Moscow*