1,721,112 research outputs found
Dynamical chaos and decoherence
No full textFidelity is a convenient tool to study the sensitivity of quantum motion under Hamiltonian perturbations. In this paper we first show that classical chaos can produce the dephasing necessary to suppress quantum interference, even in the absence of any environment. To this end we consider the fidelity of mixed states, which takes into account interference amplitudes, and directly relate its decay to the decay of an appropriate classical correlation function, which is totally unrelated to quantum phases. We then discuss the dephasing in a two-qubit system, induced by the coupling to a single-particle, deterministic chaotic environment. The latter is shown to behave as a pure dephasing many-body object which induces decoherence in the system; memory effects are also taken into account
Chaos, Order and Patterns
No full textScaling Function Dynamics; M.J. Feigenbaum. Renormalization, Zygmund Smoothness and the Epstein Class; D. Sullivan. Torus Maps; R.S. MacKay. Quasiperiodicity, ModeLocking, and Universal Scaling in Rayleigh-Bénard Convection; R.E. Ecke. Patterns in Chaos; B.V. Chirikov. Spatiotemporal Chaos; J.P. Eckmann, et al. Topics in Pattern Formation Problems and Related Questions; Y. Pomeau. Growth Patterns: From Stable Curved Fronts to Fractal Structures; Y. Couder. Simple and Complex Patterns in Coupled Map Lattices; L. Bunimovich. State Space Reconstruction and Noise; M. Casdagli, et al. Global Implications of the Implicit Function Theorem; K.A. Alligood, et al. Unfolding Complexity and Modeling Asymptotic Scaling Behavior; R. Badii, et al. Index
Numerical experiments on billiards
No full textWe investigate decay properties of correlation functions in a class of chaotic billiards. First we consider the statistics of Poincaré recurrences (induced by a partition of the billiard): the results are in agreement with theoretical bounds by Bunimovich, Sinai, and Bleher, and are consistent with a purely exponential decay of correlations out of marginality. We then turn to the analysis of the velocity-velocity correlation function: except for intermittent situations, the decay is purely exponential, and the decay rates scale in a simple way with the (uniform) curvature of the dispersing arcs. A power-law decay is instead observed when the system is equivalent to an infinite-horizon Lorentz gas. Comments are given on the behaviour of other types of correlation functions, whose decay, during the observed time scale, appears slower than exponential
Inverse Currents in Hamiltonian Coupled Transport
No full textThe occurrence of an inverse current, where the sign of the induced current is opposite to the applied force, is a highly counterintuitive phenomenon. We show that inverse currents in coupled transport (ICC) of energy and particle can occur in a one-dimensional interacting Hamiltonian system when its equilibrium state is perturbed by coupled thermodynamic forces. This seemingly paradoxical result is possible due to the self-organization occurring in the system in response to the applied forces
Power, efficiency, and fluctuations in steady-state heat engines
No full textWe consider the quality factor Q, which quantifies the trade-off between power, efficiency, and fluctuations in steady-state heat engines modeled by dynamical systems. We show that the nonlinear scattering theory, in both classical and quantum mechanics, sets the bound Q=3/8 when approaching the Carnot efficiency. On the other hand, interacting, nonintegrable, and momentum-conserving systems can achieve the value Q=1/2, which is the universal upper bound in linear response. This result shows that interactions are necessary to achieve the optimal performance of a steady-state heat engine
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