Events

Date: 19 November 2026   Time: 13:00 - 14:00     

Location: MB-503

In this review talk, we discuss the chaotic dynamics and wave packet spreading in disordered nonlinear Hamiltonian lattices, focusing on the disordered Klein-Gordon (DKG) and discrete nonlinear Schrödinger (DDNLS) models in one and two spatial dimensions. Through extensive numerical simulations, we employ a range of complementary techniques, including the maximum Lyapunov exponent (MLE), deviation vector distributions (DVDs), frequency map analysis (FMA), the Generalized Alignment Index (GALI), as well as symplectic integration schemes based on split Hamiltonians and the tangent-map method. For both models, we identify weak and strong chaos spreading regimes and find similar dynamical behaviors in one and two dimensions, highlighting the generality of the underlying chaotic mechanisms. The MLE reveals a systematic algebraic decrease of chaoticity strength with time, but chaos persists on the largest timescales investigated and does not cross over to regular dynamics, remaining sufficiently strong to sustain the subdiffusive spreading of initially localized wave packets. The DVD and FMA analyses provide complementary information on the propagation and spatial organization of chaos, while the GALI method allows us to distinguish localized from spreading chaos and to identify energy thresholds associated both with global chaotic spreading and the disappearance of chaos. We also briefly consider a one-dimensional disordered nonlinear stub lattice, showing that the characteristic weak and strong chaos subdiffusive spreading observed in conventional disordered nonlinear lattices can also occur in flat-band network geometries.