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MO: Fachverband Molekülphysik

MO 16: In Memoriam of Hermann Haken (joint session Q/MO)

MO 16.4: Hauptvortrag

Mittwoch, 12. März 2025, 12:30–13:00, HS I PI

From laser physics to nonlinear dynamics and synergetics — •Eckehard Schöll — TU Berlin, Germany

Hermann Haken was a pioneer of laser physics and developed the first full quantum theory of the laser [1]. He interpreted the laser transition as a nonequilibrium phase transition [2], and found that this is a special case of a much wider class of open systems driven far from thermodynamic equilibrium. Based upon this observation he founded the field of synergetics which deals with systems composed of many subsystems like atoms, molecules, photons, cells, etc., and shows that cooperation of the subsystems leads to spatial, temporal, or functional structures by self-organization [3]. He demonstrated that the semiclassical laser equations are mathematically equivalent to the Lorenz equation derived from fluid dynamics [4], exhibiting higher instabilities and chaos, like many other nonlinear dynamical systems in physics, chemistry, biology, medicine, and even economics, sociology and psychology. This has given rise to a plethora of new phenomena in nonequilibrium system widely studied during the past five decades. Coherence resonance is just one example which was first discovered by Haken [5], and later studied in various systems ranging from lasers to the brain.

[1] H. Haken, Laser Theory, Springer (1970, 1984).

[2] R. Graham and H. Haken, Z. Phys. 237, 31 (1970).

[3] H. Haken, Synergetics, An Introduction, Springer (1977).

[4] H. Haken, Phys. Lett. 53A, 77 (1975).

[5] G. Hu et al., Phys. Rev. Lett. 71, 807 (1993).

Keywords: Synergetics; Nonlinear laser dynamics; Nonequilibrium phase transitions; Self-organization; Chaos