Diffusion and escape times in the open-leaky standard map

TL;DR

This paper investigates how particles escape and diffuse in an open standard map with artificial leaks, revealing non-exponential escape statistics and the influence of system parameters on diffusion behavior.

Contribution

It introduces a novel analysis of escape times and diffusion in an open standard map with symmetric leaks, highlighting the non-exponential decay and long-time escape dynamics.

Findings

Escape statistics deviate from exponential decay for large perturbations

Diffusion coefficient depends on leak size and position

Particles can escape after long excursions in phase space

Abstract

We study the connection between transport phenomenon and escape rate statistics in two-dimensional standard map. For the purpose of having an open phase space, we let the momentum co-ordinate vary freely and restrict only angle with periodic boundary condition. We also define a pair of artificial holes placed symmetrically along the momentum axis where the particles might leave the system. As a consequence of the leaks the diffusion can be analysed making use of only the ensemble of survived particles. We present how the diffusion coefficient depends on the size and position of the escape regions. Since the accelerator modes and, thus, the diffusion are strongly related to the system's control parameter, we also investigate effects of the perturbation strength. Numerical simulations show that the short-time escape statistics does not follow the well-known exponential decay especially for large values of perturbation parameters. The analysis of the escape direction also supports this picture as a significant amount of particles skip the leaks and leave the system just after a longtime excursion in the remote zones of the phase space.