4,381 research outputs found
Mutual information between reflected and transmitted speckle images
We study theoretically the mutual information between reflected and
transmitted speckle patterns produced by wave scattering from disordered media.
The mutual information between the two speckle images recorded on an array of N
detection points (pixels) takes the form of long-range intensity correlation
loops, that we evaluate explicitly as a function of the disorder strength and
the Thouless number g. Our analysis, supported by extensive numerical
simulations, reveals a competing effect of cross-sample and surface spatial
correlations. An optimal distance between pixels is proven to exist, that
enhances the mutual information by a factor Ng compared to the single-pixel
scenario.Comment: 5 pages, 4 figures, + S
Near-field interactions and non-universality in speckle patterns produced by a point source in a disordered medium
A point source in a disordered scattering medium generates a speckle pattern
with non-universal features, giving rise to the so-called C_0 correlation. We
analyze theoretically the relationship between the C_0 correlation and the
statistical fluctuations of the local density of states, based on simple
arguments of energy conservation. This derivation leads to a clear physical
interpretation of the C_0 correlation. Using exact numerical simulations, we
show that C_0 is essentially a correlation resulting from near-field
interactions. These interactions are responsible for the non-universality of
C_0, that confers to this correlation a huge potential for sensing and imaging
at the subwavelength scale in complex media
Cold atom realizations of Brownian motors
Brownian motors are devices which "rectify" Brownian motion, i.e. they can
generate a current of particles out of unbiased fluctuations. Brownian motors
are important for the understanding of molecular motors, and are also promising
for the realization of new nanolelectronic devices. Among the different systems
that can be used to study Brownian motors, cold atoms in optical lattices are
quite an unusual one: there is no thermal bath and both the potential and the
fluctuations are determined by laser fields. In this article recent
experimental implementations of Brownian motors using cold atoms in optical
lattices are reviewed
Shear-free perfect fluids with a solenoidal electric curvature
We prove that the vorticity or the expansion vanishes for any shear-free
perfect fluid solution of the Einstein field equations where the pressure
satisfies a barotropic equation of state and the spatial divergence of the
electric part of the Weyl tensor is zero.Comment: 9 page
Long-Range Plasmon Assisted Energy Transfer Between Fluorescent Emitters
We demonstrate plasmon assisted energy transfer between fluorophores located
at distances up to m on the top of a thin silver film. Thanks to the
strong confinement and large propagation length of surface plasmon polaritons,
the range of the energy transfer is almost two orders of magnitude larger than
the values reported in the literature so far. The parameters driving the energy
transfer range are thoroughly characterized and are in very good agreement with
theoretically expected values.Comment: 5 pages, 4 figures, accepted for publication in Physical Review
Letter
Rayleigh scattering and atomic dynamics in dissipative optical lattices
We investigate Rayleigh scattering in dissipative optical lattices. In particular, following recent proposals [S. Guibal et al., Phys. Rev. Lett. 78, 4709 (1997); C. Jurczak et al., Phys. Rev. Lett. 77, 1727 (1996)], we study whether the Rayleigh resonance originates from the diffraction on a density grating and is therefore a probe of transport of atoms in optical lattices. It turns out that this is not the case: the Rayleigh line is instead a measure of the cooling rate, while spatial diffusion contributes to the scattering spectrum with a much broader resonance
The ALICE detector and trigger strategy for diffractive and electromagnetic processe
The ALICE detector at the Large Hadron Collider (LHC) consists of a central
barrel, a muon spectrometer, zero degree calorimeters and additional detectors
which are used for trigger purposes and for event classification. The main
detector systems of relevance for measuring diffractive and electromagnetic
processes are described. The trigger strategy for such measurements is
outlined. The physics potential of studying diffractive and electromagnetic
processes at the LHC is presented by discussing possible signatures of the
Odderon.Comment: 6 pages, 8 figures, Proceedings workshop on "High energy photon
collisions at the LHC", CERN, apr 22-25, 200
- …