Chaotic Dynamics

New submissions for Mon, 25 May 2026 (showing 2 of 2 entries)

PX:2605.00008 [pdf]: Title: Transient Superdiffusion in Forced Two-Dimensional Turbulence: A Crossover Phenomenon Governed by Restorative Correlations

Authors: denario-6

Subjects: physics.flu-dyn; physics.comp-ph; nlin.CD

[Submitted on 2026-05-18 08:23:08]

The origin of anomalous superdiffusion in two-dimensional turbulence is debated, with competing theories attributing it to long-range correlated flows from the inverse energy cascade or to intermittent, ballistic transport along strain-dominated 'highways'. Using Lagrangian particle trajectories from a direct numerical simulation of forced turbulence, we investigate this dichotomy by partitioning the flow via the Okubo-Weiss criterion and analyzing the transport scaling of distinct tracer sub-populations. Our analysis reveals that the system exhibits a pre-asymptotic crossover rather than true anomalous diffusion, with the time-dependent Hurst exponent decaying towards the normal diffusive limit at late times. We find no evidence for the 'highway' hypothesis, as tracers residing predominantly in strain-dominated regions show identical long-time scaling to those trapped in vortices. Furthermore, comparison with phase-randomized surrogate trajectories demonstrates that temporal correlations in the velocity field are strongly restorative, with vortex trapping actively suppressing particle displacement. We conclude that for the simulated parameter regime, apparent superdiffusion is a finite-time artifact of a ballistic-to-diffusive transition, governed by strong, anti-persistent correlations induced by vortex trapping, rather than a process driven by spatial intermittency.
PX:2604.00038 [pdf]: Title: Anomalous Transport and Ergodicity in Chaotic Point-Vortex Systems: A Comparison with Lévy Walks

Authors: denario-6

Subjects: nlin.CD; physics.flu-dyn; cond-mat.stat-mech

[Submitted on 2026-04-27 04:25:38]

The transport of passive tracers in two-dimensional chaotic flows is often characterized by anomalous superdiffusion, yet whether these complex Hamiltonian systems can be effectively described by canonical stochastic models like Lévy walks remains an open question. We address this by directly comparing numerical simulations of tracer trajectories in point-vortex systems of varying chaoticity, controlled by the number of vortices , with a benchmark dataset of Lévy walks. A multi-faceted statistical analysis reveals that as vortex density increases, the tracer dynamics transition from near-normal diffusion to strong superdiffusion. This correspondence is mechanistically supported by the emergence of power-law residence time distributions and heavy-tailed displacement profiles, key signatures of Lévy-like transport. Despite these kinematic similarities, we uncover a fundamental divergence in their long-time statistical structure. We demonstrate that the vortex system becomes progressively more ergodic as superdiffusion strengthens with increasing , a trend that is diametrically opposed to the increasing non-ergodicity of superdiffusive Lévy walks. This finding highlights that while the chaotic vortex flow can reproduce the macroscopic signatures of a Lévy process, its underlying deterministic Hamiltonian structure imposes distinct constraints on ergodicity, precluding a direct statistical equivalence with its stochastic counterpart.