Colloquia 2006

Chaos and pseudochaos in complex systems and statistical mechanics

Prof. Angelo Vulpiani,
Universit di Roma La Sapienza, Roma.

Date

4-5 p.m., Thursday, 23 February, 2006 .

Location

School of Physics Common Room
Room 64 Old Main Building
The University of New South Wales

Abstract
Some aspects of the predictability problem in dynamical systems are reviewed with a special attention to finite-resolution effects.

Then, we focus on the problems concerning the determination of the microscopic nature of diffusion by means of data analysis and the origin of diffusion in non-chaotic systems. As an example, we consider one dimensional non chaotic map but with random quenched discontinuities and quasi-periodic forcing. The model is constructed as non-chaotic approximations of chaotic maps showing deterministic diffusion, and represent one-dimensional versions of a Lorentz gas with polygonal obstacles (e.g., the Ehrenfest wind tree model). The model exhibits, in a wide range of the parameters, the same diffusive behavior of the corresponding chaotic versions. We present evidence of two sufficient ingredients for diffusive behavior in one-dimensional, non-chaotic systems:
i) a finite-size, algebraic instability mechanism, and
ii) a mechanism that suppresses periodic orbits.

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