New Type of Chaos Discovered

For 40 years, it has been known that lasers utilizing time-delayed feedback of the original signal can cause chaotic intensity fluctuations (top of figure, second image). However, for many potential applications, this type of chaos is too sensitive to perturbations.

The discovery made by the theoretical physicists David Müller, Dr. Andreas Otto, and Prof. Günter Radons from Chemnitz University of Technology could change this situation. They found that a small modification of such experiments – a periodic modulation of the delay – can lead to totally different, novel intensity variations, which are characterized by sequences of plateaus (bottom of figure, second image).

Special features of this type of signal, which is now called laminar chaos, are on one hand the robustness of the location and the form of the plateaus against perturbations, and on the other hand that the heights vary chaotically from plateau to plateau, and thus can serve as a carrier of information.

This high robustness of the information content against perturbations makes this newly discovered form of chaos interesting for modern information technologies such as fast optical realizations of chaos communication, chaos cryptography, or reservoir computing.

The fundamental importance of the research results obtained by the theoretical physicists has made it possible to already publish two articles about their work in the most internationally renowned journal, ‘Physical Review Letters’.

Over the last years, Prof. Günter Radons’s group has achieved such a reputation in the field that it was possible to assemble the worldwide leading experts in delay systems during the upcoming 675. WE-Heraeus Seminar: Delayed Complex Systems 2018, which will take place in the Bad Honnef Physikzentrum from July 2 – 5 (Scientific organization: A. Otto, G. Radons, Chemnitz University of Technology, and Wolfram Just, Queen Mary University of London).

Background knowledge: Chaos & Delay

In physics, the term ‘chaos’ characterizes a type of motion which appears very irregular but at the same time follows definite laws. Almost all systems show this feature, which makes it impossible to make long-term predictions. Well-known examples from everyday life are the weather or the drawing of lottery numbers. Laser light or the size of bacterial colonies can also vary chaotically. ‘Delay’ is a special term which characterizes the time between cause and effect. In many cases, it cannot be ignored and can bring about extremely complicated patterns of movement.

Background knowledge: Wilhelm and Else Heraeus Seminar

The organization of scientific seminars is the oldest and best known funding activity of the Wilhelm and Else Heraeus Foundation. The program has brought together more than 30,000 participants since its establishment in 1975, more than one third from foreign countries. The topics of the seminars cover all fields of modern physics including areas of intersection with other disciplines. WE-Heraeus Seminars encompass the current frontiers of science and are internationally oriented. WE-Heraeus Seminars are applied for by one or several scientists according to the rules of the foundation. After evaluation and recommendation by the scientific advisory committee, the foundation council can grant an approval. The seminars are run by the foundation in close cooperation with the applicant(s) (i.e. the scientific organizers).

The Chemnitz physicists’ articles in ‘Physical Review Letters’:
D. Müller, A. Otto and G. Radons: Laminar Chaos, Phys. Rev. Lett. 120, 084102 (2018).
A. Otto, D. Müller and G. Radons: Universal Dichotomy for Dynamical Systems with Variable Delay, Phys. Rev. Lett. 118, 044104 (2017).

Further information can be obtained from Prof. Günter Radons, Chair of Complex Systems and Nonlinear Dynamics, Institute of Physics, Telefon 0371 531-21870, E-Mail radons@physik.tu-chemnitz.de.