The Experts below are selected from a list of 20298 Experts worldwide ranked by ideXlab platform
Ad Lagendijk - One of the best experts on this subject based on the ideXlab platform.
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Point scatterers for classical waves
Reviews of Modern Physics, 1998Co-Authors: Pedro De Vries, David V Van Coevorden, Ad LagendijkAbstract:The authors present a closed formulation of Resonant Point scatterers for classical-wave propagation problems. A Green’s-function approach is employed in which all the small-distance singularities are regularized. Application of Point scatterers considerably simplifies multiple-scattering calculations needed, for instance, for understanding the optical properties of dense cold gases and optical lattices. In the case of the vector description of light, it is shown that two different regularization parameters are required in order to obtain physically meaningful results. One parameter is related to the physical size of the Pointlike scattering particle, while the other is connected to its dynamic properties. All parameters involved are defined in terms of physical observables leading to a complete and self-consistent treatment. The applicability of the Point-scatterer model to several physical models is demonstrated. We calculate the local density of states of waves in the presence of one Resonant Point scatterer. For the vector case, the bare polarizability is shown to enter the local density of states. For a collection of Resonant Point dipoles, the Lorentz-Lorenz relation for the dielectric constant is derived for cubic lattices and for disordered arrangements. [S0034-6861(98)00302-X]
I M Sokolov - One of the best experts on this subject based on the ideXlab platform.
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ioffe regel criterion for anderson localization in the model of Resonant Point scatterers
Physical Review B, 2018Co-Authors: S E Skipetrov, I M SokolovAbstract:We establish a phase diagram of a model in which scalar waves are scattered by Resonant Point scatterers (atoms) pinned at random positions in the free three-dimensional (3D) space. A transition to Anderson localization takes place in a narrow frequency band near the resonance frequency provided that the number density of scatterers $\rho$ exceeds a critical value $\rho_c \simeq 0.08 k_0^{3}$, where $k_0$ is the wave number in the free space. The localization condition $\rho > \rho_c$ can be rewritten as $k_0 \ell_0 < 1$, where $\ell_0$ is the on-resonance mean free path in the independent-scattering approximation. At mobility edges, the decay of the average amplitude of a monochromatic plane wave is not purely exponential and the growth of its phase is nonlinear with the propagation distance. This makes it impossible to define the mean free path $\ell$ and the effective wave number $k$ in a usual way. If the latter are defined as an effective decay length of the intensity and an effective growth rate of the phase of the average wave field, the Ioffe-Regel parameter $(k\ell)_c$ at the mobility edges can be calculated and takes values from 0.4 to 1.1 depending on $\rho$. Thus, the Ioffe-Regel criterion of localization $k\ell < (k\ell)_c = \mathrm{const} \sim 1$ is valid only qualitatively and cannot be used as a quantitative condition of Anderson localization in 3D.
Paul Stuart Cally - One of the best experts on this subject based on the ideXlab platform.
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wave resonances and the partition of energy in ideal compressible magnetohydrodynamic fluids
Physics of Plasmas, 2012Co-Authors: Claude Zorzan, Paul Stuart CallyAbstract:Phase mixing and Resonant absorption are two processes that have been under scrutiny for some time because of their role in wave damping and in providing a mechanism for heating space and laboratory plasmas. The accumulation or absorption of energy that develops within a Resonant layer is usually attributed to a logarithmic singularity, but it will be shown that this build up of energy is inextricably tied to a discontinuity in the fluid displacement at the Resonant Point. This change in the dynamics of the problem will be examined by establishing a partition of energy that identifies and isolates the individual resonances within the fluid. The partition is based on a variational description of the Fourier transformed equations and is guided by an electrical model of the MHD system that not only illustrates the Resonant structure threading the fluid but also exposes the mechanism driving the Resonant absorption process. A simplified version of this model is then constructed to help determine the approximate rate of energy absorption.
Pedro De Vries - One of the best experts on this subject based on the ideXlab platform.
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Point scatterers for classical waves
Reviews of Modern Physics, 1998Co-Authors: Pedro De Vries, David V Van Coevorden, Ad LagendijkAbstract:The authors present a closed formulation of Resonant Point scatterers for classical-wave propagation problems. A Green’s-function approach is employed in which all the small-distance singularities are regularized. Application of Point scatterers considerably simplifies multiple-scattering calculations needed, for instance, for understanding the optical properties of dense cold gases and optical lattices. In the case of the vector description of light, it is shown that two different regularization parameters are required in order to obtain physically meaningful results. One parameter is related to the physical size of the Pointlike scattering particle, while the other is connected to its dynamic properties. All parameters involved are defined in terms of physical observables leading to a complete and self-consistent treatment. The applicability of the Point-scatterer model to several physical models is demonstrated. We calculate the local density of states of waves in the presence of one Resonant Point scatterer. For the vector case, the bare polarizability is shown to enter the local density of states. For a collection of Resonant Point dipoles, the Lorentz-Lorenz relation for the dielectric constant is derived for cubic lattices and for disordered arrangements. [S0034-6861(98)00302-X]
S E Skipetrov - One of the best experts on this subject based on the ideXlab platform.
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ioffe regel criterion for anderson localization in the model of Resonant Point scatterers
Physical Review B, 2018Co-Authors: S E Skipetrov, I M SokolovAbstract:We establish a phase diagram of a model in which scalar waves are scattered by Resonant Point scatterers (atoms) pinned at random positions in the free three-dimensional (3D) space. A transition to Anderson localization takes place in a narrow frequency band near the resonance frequency provided that the number density of scatterers $\rho$ exceeds a critical value $\rho_c \simeq 0.08 k_0^{3}$, where $k_0$ is the wave number in the free space. The localization condition $\rho > \rho_c$ can be rewritten as $k_0 \ell_0 < 1$, where $\ell_0$ is the on-resonance mean free path in the independent-scattering approximation. At mobility edges, the decay of the average amplitude of a monochromatic plane wave is not purely exponential and the growth of its phase is nonlinear with the propagation distance. This makes it impossible to define the mean free path $\ell$ and the effective wave number $k$ in a usual way. If the latter are defined as an effective decay length of the intensity and an effective growth rate of the phase of the average wave field, the Ioffe-Regel parameter $(k\ell)_c$ at the mobility edges can be calculated and takes values from 0.4 to 1.1 depending on $\rho$. Thus, the Ioffe-Regel criterion of localization $k\ell < (k\ell)_c = \mathrm{const} \sim 1$ is valid only qualitatively and cannot be used as a quantitative condition of Anderson localization in 3D.