2,495 research outputs found
Bouncing localized structures in a liquid-crystal light-valve experiment
Experimental evidence of bouncing localized structures in a nonlinear optical
system is reported.Comment: 4 page
Spatiotemporal chaos induces extreme events in an extended microcavity laser
Extreme events such as rogue wave in optics and fluids are often associated
with the merging dynamics of coherent structures. We present experimental and
numerical results on the physics of extreme events appearance in a spatially
extended semiconductor microcavity laser with intracavity saturable absorber.
This system can display deterministic irregular dynamics only thanks to spatial
coupling through diffraction of light. We have identified parameter regions
where extreme events are encountered and established the origin of this
dynamics in the emergence of deterministic spatiotemporal chaos, through the
correspondence between the proportion of extreme events and the dimension of
the strange attractor
JPEG steganography with particle swarm optimization accelerated by AVX
Digital steganography aims at hiding secret messages in digital data transmitted over insecure channels. The JPEG format is prevalent in digital communication, and images are often used as cover objects in digital steganography. Optimization methods can improve the properties of images with embedded secret but introduce additional computational complexity to their processing. AVX instructions available in modern CPUs are, in this work, used to accelerate data parallel operations that are part of image steganography with advanced optimizations.Web of Science328art. no. e544
Universal shape law of stochastic supercritical bifurcations: Theory and experiments
A universal law for the supercritical bifurcation shape of transverse
one-dimensional (1D) systems in presence of additive noise is given. The
stochastic Langevin equation of such systems is solved by using a Fokker-Planck
equation leading to the expression for the most probable amplitude of the
critical mode. From this universal expression, the shape of the bifurcation,
its location and its evolution with the noise level are completely defined.
Experimental results obtained for a 1D transverse Kerr-like slice subjected to
optical feedback are in excellent agreement.Comment: 5 pages, 5 figure
The X-CLASS - redMaPPer galaxy cluster comparison: I. Identification procedures
We performed a detailed and, for a large part interactive, analysis of the
matching output between the X-CLASS and redMaPPer cluster catalogues. The
overlap between the two catalogues has been accurately determined and possible
cluster positional errors were manually recovered. The final samples comprise
270 and 355 redMaPPer and X-CLASS clusters respectively. X-ray cluster matching
rates were analysed as a function of optical richness. In a second step, the
redMaPPer clusters were correlated with the entire X-ray catalogue, containing
point and uncharacterised sources (down to a few 10^{-15} erg s^{-1} cm^{-2} in
the [0.5-2] keV band). A stacking analysis was performed for the remaining
undetected optical clusters. Main results show that neither of the wavebands
misses any massive cluster (as coded by X-ray luminosity or optical richness).
After correcting for obvious pipeline short-comings (about 10% of the cases
both in optical and X-ray), ~50% of the redMaPPer (down to a richness of 20)
are found to coincide with an X-CLASS cluster; when considering X-ray sources
of any type, this fraction increases to ~ 80%; for the remaining objects, the
stacking analysis finds a weak signal within 0.5 Mpc around the cluster optical
centers. The fraction of clusters totally dominated by AGN-type emission
appears to be of the order of a few percent. Conversely ~ 40% of the X-CLASS
clusters are identified with a redMaPPer (down to a richness of 20) - part of
the non-matches being due to the fact that the X-CLASS sample extends further
out than redMaPPer (z<1 vs z<0.6); extending the correlation down to a richness
of 5, raises the matching rate to ~ 65%.Comment: 15 pages, 20 figures, 2 table
Extreme events prediction from nonlocal partial information in a spatiotemporally chaotic microcavity laser
The forecasting of high-dimensional, spatiotemporal nonlinear systems has
made tremendous progress with the advent of model-free machine learning
techniques. However, in real systems it is not always possible to have all the
information needed; only partial information is available for learning and
forecasting. This can be due to insufficient temporal or spatial samplings, to
inaccessible variables or to noisy training data. Here, we show that it is
nevertheless possible to forecast extreme events occurrence in incomplete
experimental recordings from a spatiotemporally chaotic microcavity laser using
reservoir computing. Selecting regions of maximum transfer entropy, we show
that it is possible to get higher forecasting accuracy using nonlocal data vs
local data thus allowing greater warning times, at least twice the time horizon
predicted from the nonlinear local Lyapunov exponent
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