782 research outputs found
Anderson localization as position-dependent diffusion in disordered waveguides
We show that the recently developed self-consistent theory of Anderson
localization with a position-dependent diffusion coefficient is in quantitative
agreement with the supersymmetry approach up to terms of the order of
(with the dimensionless conductance in the absence of interference
effects) and with large-scale {\it ab-initio} simulations of the classical wave
transport in disordered waveguides, at least for . In the
latter case, agreement is found even in the presence of absorption. Our
numerical results confirm that in open disordered media, the onset of Anderson
localization can be viewed as position-dependent diffusion.Comment: 6 pages, 3 figure
Stokes parameters for light scattering from a Faraday-active sphere
We present an exact calculation for the scattering of light from a single
sphere made of Faraday-active material, to first order in the external magnetic
field. We use a recent expression for the T-matrix of a Mie scatterer in a
magnetic field to compute the Stokes parameters in single scattering that
describe completely flux and polarization of the scattered light.Comment: 17 pages, 5 figures, Latex, accepted for publication in JQSR
Transverse confinement of waves in 3D random media
We study the transmission of a tightly focused beam through a thick slab of
3D disordered medium in the Anderson localized regime. We show that the
transverse profile of the transmitted beam exhibits clear signatures of
Anderson localization and that its mean square width provides a direct measure
of the localization length. For a short incident pulse, the width is
independent of absorption.Comment: 4 pages, 3 figure
Weak localization of short pulses in disordered waveguides
We consider the phenomenon of weak localization of a short wave pulse in a
quasi-1D disordered waveguide. We show that the long-time decay of the average
transmission coefficient is not purely exponential, in contradiction with
predictions of the diffusion theory. The diffusion theory breaks down
completely for times exceeding the Heisenberg time. We also study the survival
probability of a quantum particle in a disordered waveguide and compare our
results with previous calculations using the super-symmetric nonlinear sigma
model.Comment: 4 pages, to appear in Acta Phys. Pol. A (Proceedings of the 2nd
Workshop on Quantum Chaos and Localization Phenomena, May 19-22, 2005,
Warsaw
Transfer of linear momentum from the quantum vacuum to a magnetochiral molecule
In a recent publication [Phys. Rev. Lett. 111, 143602] we have shown using a
QED approach that, in the presence of a magnetic field, the quantum vacuum
coupled to a chiral molecule provides a kinetic momentum directed along the
magnetic field. Here we explain the physical mechanisms which operate in the
transfer of momentum from the vacuum to the molecule. We show that the
variation of the molecular kinetic energy originates from the magnetic energy
associated with the vacuum correction to the magnetization of the molecule. We
carry out a semiclassical calculation of the vacuum momentum and compare the
result with the QED calculation.Comment: minor corrections made to agree with the published versio
Magneto-chiral scattering of light: a new optical manifestation of chirality
We have investigated multiple scattering of light in systems subject to
magneto-chiral (MC) effects. Our medium consists of magneto-optically active
dipoles placed in a chiral geometry under the influence of an external magnetic
field. We have calculated, for the first time, the total and the differential
scattering MC cross sections of this system, explicitely showing that they are
proportional to pseudoscalar quantities. This provides a new optical measure
for the degree of chirality, a pseudoscalar g, of an arbitrary geometrical
configuration of scatterers based on its scattering properties. We have
calculated g for some simple chiral systems and we have even used it to probe
the degree of optical chirality of random systems. Finally, we have compared
with other recently defined chiral measures in literature.Comment: 18 pages, 6 figures, RevTeX. Submitted to PR
Anderson Localization of Matter Waves in 3D Anisotropic Disordered Potentials
Using a cutoff-free formulation of the coherent transport theory, we show
that the interference terms at the origin of localization strongly affect the
transport anisotropy. In contrast to the common hypothesis, we then find that
the anisotropies of incoherent and coherent diffusion are significantly
different, in particular at criticality. There, we show that the coherent
transport anisotropy is mainly determined by the properties of the
disorder-averaged effective scattering medium while the incoherent transport
contributions become irrelevant
Assimilation of satellite data and insitu data for the improvement of global radiation maps in the Netherlands
For this research, two satellite products were used to see if it was possible to improve the resolution and quality of the global radiation interpolation in the Netherlands. The ïŹrst data source was from the Climate Monitoring Satellite Application Facility (CM-SAF). The second data source was the Surface Insolation under Clear and Cloudy Skies (SICCS) from the KNMI. Both products were available for the period of January 2006 to December 2011 and came in the form of images with monthly and daily averages. To combine the satellite images with the in- put provided by the KNMIâs 32 measurement stations, these interpolation/merging methods were used: Thin Plate Splines (TPS), Mean Bias interpolation (MB), Interpolated Bias interpolation (IB), Kriging with External Drift; Exponential model (KED-EXP) & Kriging with External Drift; Spherical model (KED-SPH) All these methods made use of the in-situ measurements as main input for the interpolation and all methods except TPS used the satellite products as auxiliary data. Interpolations were made for the average of the six year period and on monthly measurements, for each month, in each year. Daily interpolations were made for April 2010 until July 2010. Different validation methods were used to analyze the output. The results showed that; for the six year average both products and all interpolation methods did a good job on predicting global radiation. The R2 was lowest for the IB on the CM-SAF product with a value of 0.19. However, the MAPE (mean absolute percentage error) did not exceed 1.39% on the CM-SAF product and 1.42% on the SICCS product. These values corresponded with an absolute bias of 1.77 W/m2 and 1.8 W/m2. The monthly results showed similar results. The R2 values tended to differ more, especially in the IB and MB interpolation. In most cases this could be explained by the quality of the Satellite images. The MAPE was low in all cases. A maximum MAPE of 8.38% was found (when using proper satellite images), in November, which corresponded with an absolute bias of ± 4 W/m2. Data splitting returned similar results. MAPEâs did increase up to 9.27% when leaving out 1/4th of the measurement stations but this value corresponds with an absolute bias of 2.71W/m2. These low absolute errors showed that all interpolation methods return an accurate interpolation. However, because the interpolation methods rely on the quality of the satellite images, the SICCS product would be a better product. These images were complete in all months while the CM-SAF product lacked data in December. Since it turned out that all interpolations performed well, daily data was analyzed for the period of April until July 2010. It turned out that for the daily data KED and the IB interpolations performed signiïŹcantly better than the TPS or MB interpolation. The biggest average MAPE was found for the TPS method (10.7% in May). The smallest average errorof0%wasfoundfortheIBmethod. How- ever this method was paired with very low R2 values which made the model unpredictable. The average KED R2 and MAPE ranged from 0.57 to 0.75 and from 0.08% to 0.95 %. This made the method a stable and accurate interpolation method. The satellite images on their own would not be good enough to use directly as a global radiation map, for this time interval. The over- and underestimated bias of the satellite images ranged from -89.63 to 64.49 W/m2. This showed that, a combination of station data and satellite data would improve the quality and resolution of daily global radiation maps
Role of mean free path in spatial phase correlation and nodal screening
We study the spatial correlation function of the phase and its derivative,
and related, fluctuations of topological charge, in two and three dimensional
random media described by Gaussian statistics. We investigate their dependence
on the scattering mean free path.Comment: 7 pages, 6 figures. submitted to Europhys. Let
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