3,561 research outputs found

    Wave Decoherence for the Random Schroedinger Equation with Long-Range Correlations

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    In this paper, we study the decoherence of a wave described by the solution to a Schroedinger equation with a time-dependent random potential. The random potential is assumed to have slowly decaying correlations. The main tool to analyze the decoherence behaviors is a properly rescaled Wigner transform of the solution of the random Schroedinger equation. We exhibit anomalous wave decoherence effects at different propagation scales.Comment: 29 pages, 5 figures. arXiv admin note: text overlap with arXiv:1110.330

    Rigorous derivation of Lindblad equations from quantum jumps processes in 1D

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    We are interested by the behaviour of a 1D single heavy particle, interacting with an environment made of very fast particles in a thermal state. Assuming that the interactions are instantaneous, we construct an appropriate quantum jump process for the density operator of the heavy particle. In a weak-coupling limit (many interactions with few effect), we show that the solutions of jump process converge in law in the appropriate space towards the solution of a Lindbald master equation. To the best of our knowledge, it seems to be the first rigorous derivation of a dissipative quantum evolution equation.Comment: 21 page

    Loss of Resolution for the Time Reversal of Waves in Random Underwater Acoustic Channels

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    In this paper we analyze a time-reversal experiment in a random underwater acoustic channel. In this kind of waveguide with semi-infinite cross section a propagating field can be decomposed over three kinds of modes: the propagating modes, the radiating modes and the evanescent modes. Using an asymptotic analysis based on a separation of scales technique we derive the asymptotic form of the the coupled mode power equation for the propagating modes. This approximation is used to compute the transverse profile of the refocused field and show that random inhomogeneities inside the waveguide deteriorate the spatial refocusing. This result, in an underwater acoustic channel context, is in contradiction with the classical results about time-reversal experiment in other configurations, for which randomness in the propagation medium enhances the refocusing.Comment: 31 pages, 11 figure

    Pomeron Physics at the LHC

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    We present current and ongoing research aimed at identifying Pomeron effects at the LHC in both the weak and strongly coupled regimes of QCD.Comment: 11 pages, 9 figures, 1 table. ISMD-2017 proceedings, will be published on-line on the EPJ Web of Conferences; References adde

    A stochastic framework for secondary metastatic emission

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    In this note, we bridge a gap between two descriptions of metastatic growth. The first is a deterministic model introduced by Iwata et al. and includes secondary metastatic emission, the other is a stochastic description without secondary metastatic emission. Here we propose a stochastic model with secondary metastatic emission, described in terms of a cascade of Poisson point processes. We show that the Iwata model describes the mean behaviour of our stochastic model. Furthermore, the variation due to the stochasticity of emission is evaluated for published clinical parameters

    Fractional White-Noise Limit and Paraxial Approximation for Waves in Random Media

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    International audienceThis work is devoted to the asymptotic analysis of high frequency wave propagation in random media with long-range dependence. We are interested in two asymptotic regimes, that we investigate simultaneously: the paraxial approximation, where the wave is collimated and propagates along a privileged direction of propagation, and the white-noise limit, where random fluctuations in the background are well approximated in a statistical sense by a fractional white noise. The fractional nature of the fluctuations is reminiscent of the long-range correlations in the underlying random medium. A typical physical setting is laser beam propagation in turbulent atmosphere. Starting from the high frequency wave equation with fast non-Gaussian random oscillations in the velocity field, we derive the fractional Itô-Schrödinger equation, that is a Schrödinger equation with potential equal to a fractional white noise. The proof involves a fine analysis of the backscattering and of the coupling between the propagating and evanescent modes. Because of the long-range dependence, classical diffusion-approximation theorems for equations with random coefficients do not apply, and we therefore use moment techniques to study the convergence
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