Random fluctuation leads to forbidden escape of particles

TL;DR

This paper demonstrates that small random fluctuations can cause particles initially trapped inside invariant structures in Hamiltonian systems to escape, transforming their dynamics to resemble hyperbolic systems and revealing universal decay laws.

Contribution

It introduces the concept that finite noise induces escape from KAM islands, showing a transition from non-hyperbolic to hyperbolic-like behavior in Hamiltonian scattering.

Findings

Particles inside KAM islands escape within finite time under noise.

The escape time distribution follows a hyperbolic decay law.

A quadratic power law relates noise amplitude to decay rate.

Abstract

A great number of physical processes are described within the context of Hamiltonian scattering. Previous studies have rather been focused on trajectories starting outside invariant structures, since the ones starting inside are expected to stay trapped there forever. This is true though only for the deterministic case. We show however that, under finitely small random fluctuations of the field, trajectories starting inside Arnold-Kolmogorov-Moser (KAM) islands escape within finite time. The non-hyperbolic dynamics gains then hyperbolic characteristics due to the effect of the random perturbed field. As a consequence, trajectories which are started inside KAM curves escape with hyperbolic-like time decay distribution, and the fractal dimension of a set of particles that remain in the scattering region approaches that for hyperbolic systems. We show a universal quadratic power law relating the exponential decay to the amplitude of noise. We present a random walk model to relate this distribution to the amplitude of noise, and investigate this phenomena with a numerical study applying random maps.