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artículo con referato
"Sensitivity to Perturbations in a Quantum Chaotic Billiard"
D.A. Wisniacki, E.G. Vergini, H.M. Pastawski and F.M. Cucchietti
Phys. Rev. E 65(5): Rapid Comm. (2002) 055206(R)/1-4
The Loschmidt echo (LE) measures the ability of a system to return to the initial state after a forward quantum evolution followed by a backward perturbed one. It has been conjectured that the echo of a classically chaotic system decays exponentially, with a decay rate given by the minimum between the width Γ of the local density of states and the Lyapunov exponent. As the perturbation strength is increased one obtains a cross-over between both regimes. These predictions are based on situations where the Fermi Golden Rule (FGR) is valid. By considering a paradigmatic fully chaotic system, the Bunimovich stadium billiard, with a perturbation in a regime for which the FGR manifestly does not work, we find a crossover from Γ to Lyapunov decay. We find that, challenging the analytic interpretation, these conjetures are valid even beyond the expected range.
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