3,479 research outputs found
Wave Decoherence for the Random Schroedinger Equation with Long-Range Correlations
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
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
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
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
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
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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