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DY: Fachverband Dynamik und Statistische Physik

DY 15: ISPS Intersectional Poster Session

DY 15.17: Poster

Tuesday, March 15, 2011, 18:00–20:00, P1

Stability induced by chaos and disorder in the time reversal focalization — •Hernan L. Calvo^1,2 and Horacio M. Pastawski¹ — ¹Instituto de Fisica Enrique Gaviola and FaMAF UNC, 5000 Cordoba, Argentina — ²Institut für Theoretische Physik A, RWTH Aachen University, D-52056 Aachen, Germany

The experimental procedure known as the time reversal mirror successfully achieves the focusing of a local excitation after its propagation through a chaotic or disordered medium. An initially localized pulse that becomes in a series of low amplitude reverberations is registered by a transducer that re-injects the signal in the reverse temporal order. This enables the focalization of the original pulse whose quality increases with the level of disorder in the system. We study the stability of this phenomenon against two irreversible processes: the escape in an open cavity, and a closed cavity under the effects of an external perturbation. Within a semiclassical approach in terms of time-dependent trajectories, the multiple reflections of the redundant registration yield a focalization signal that can be related with the Loschmidt echo amplitude. Both situations describe a Fermi Golden Rule regime, where the decay of the focalization is dominated by the perturbation strength. However, in the closed cavity this decay diminishes with the Lyapunov exponent of the system. This counter-intuitive result is a form of the quantum Zeno effect, which provides a new interpretation of the remarkable stability of the experiments.