2,962 research outputs found
The twilight zone in the parametric evolution of eigenstates: beyond perturbation theory and semiclassics
Considering a quantized chaotic system, we analyze the evolution of its
eigenstates as a result of varying a control parameter. As the induced
perturbation becomes larger, there is a crossover from a perturbative to a
non-perturbative regime, which is reflected in the structural changes of the
local density of states. For the first time the {\em full} scenario is explored
for a physical system: an Aharonov-Bohm cylindrical billiard. As we vary the
magnetic flux, we discover an intermediate twilight regime where perturbative
and semiclassical features co-exist. This is in contrast with the {\em simple}
crossover from a Lorentzian to a semicircle line-shape which is found in
random-matrix models.Comment: 4 pages, 4 figures, improved versio
Dynamic reorganization of vortex matter into partially disordered lattices
We report structural evidence of dynamic reorganization in vortex matter in
clean NbSe by joint small angle neutron scattering and ac-susceptibility
measurements. The application of oscillatory forces in a transitional region
near the order-disorder transition results in robust bulk vortex lattice
configurations with an intermediate degree of disorder. These
dynamically-originated configurations correlate with intermediate pinning
responses previously observed, resolving a long standing debate regarding the
origin of such responses.Comment: 9 pages, 7 figures. To be published in Physical Review Letter
Photonic heterostructures with Levy-type disorder: statistics of coherent transmission
We study the electromagnetic transmission through one-dimensional (1D)
photonic heterostructures whose random layer thicknesses follow a long-tailed
distribution --L\'evy-type distribution. Based on recent predictions made for
1D coherent transport with L\'evy-type disorder, we show numerically that for a
system of length (i) the average for
for , being the
exponent of the power-law decay of the layer-thickness probability
distribution; and (ii) the transmission distribution is independent of
the angle of incidence and frequency of the electromagnetic wave, but it is
fully determined by the values of and .Comment: 4 pages, 4 figure
Regularization dependence of the OTOC. Which Lyapunov spectrum is the physical one?
We study the contour dependence of the out-of-time-ordered correlation function (OTOC) both in weakly coupled field theory and in the Sachdev-Ye-Kitaev (SYK) model. We show that its value, including its Lyapunov spectrum, depends sensitively on the shape of the complex time contour in generic weakly coupled field theories. For gapless theories with no thermal mass, such as SYK, the Lyapunov spectrum turns out to be an exception; their Lyapunov spectra do not exhibit contour dependence, though the full OTOCs do. Our result puts into question which of the Lyapunov exponents computed from the exponential growth of the OTOC reflects the actual physical dynamics of the system. We argue that, in a weakly coupled Phi(4) theory, a kinetic theory argument indicates that the symmetric configuration of the time contour, namely the one for which the bound on chaos has been proven, has a proper interpretation in terms of dynamical chaos. Finally, we point out that a relation between these OTOCs and a quantity which may be measured experimentally - the Loschmidt echo - also suggests a symmetric contour configuration, with the subtlety that the inverse periodicity in Euclidean time is half the physical temperature. In this interpretation the chaos bound reads lambda <= 2 pi/beta=pi T-physical
Expected exponential loss for gaze-based video and volume ground truth annotation
Many recent machine learning approaches used in medical imaging are highly
reliant on large amounts of image and ground truth data. In the context of
object segmentation, pixel-wise annotations are extremely expensive to collect,
especially in video and 3D volumes. To reduce this annotation burden, we
propose a novel framework to allow annotators to simply observe the object to
segment and record where they have looked at with a \$200 eye gaze tracker. Our
method then estimates pixel-wise probabilities for the presence of the object
throughout the sequence from which we train a classifier in semi-supervised
setting using a novel Expected Exponential loss function. We show that our
framework provides superior performances on a wide range of medical image
settings compared to existing strategies and that our method can be combined
with current crowd-sourcing paradigms as well.Comment: 9 pages, 5 figues, MICCAI 2017 - LABELS Worksho
Stochastic simulation of daily rainfall fields conditioned on atmospheric circulation patterns and orographic effects.
The objective of the current work is to present a methodology for simulation of stochastic spatial distributed rainfall fields at the daily time step. For this purpose, we develop a geo-stochastic rainfall generating process (SRGP) to
generate spatially distributed rainfall fields at daily time scale, that respect the
spatial correlation structure of historically observed precipitation, while taking into account important factors that influence the development of observed
spatial patterns. For each day, a spatially distributed rainfall field is generated
from a pre-specified SRGP, selected based on atmospheric synoptic conditions relevant for that day. Each SRGP is simulated by applying the concept of double kriging, as the product of the spatial amount of rainfall and the spatial occurrence of rainfall by sequential simulation (sequential Gaussian simulation and sequential indicator simulation respectively). The SRGP can account for spatial rainfall nonstationarity
related to orographic effects, and can be incorporated as part of a downscaling technique in the context of climate change impact studies. A case study for the Upper Guadiana basin (Spain) is presented that shows the ability of the method to reproduce various spatio-temporal characteristics of precipitation.Peer ReviewedPostprint (published version
Molecular Mechanism and Potential Targets for Blocking HPV-Induced Lesion Development
Persistent infection with high-risk HPV is the etiologic agent associated with the development of cervical cancer (CC) development. However, environmental, social, epidemiological, genetic, and host factors may have a joint influence on the risk of disease progression. Cervical lesions caused by HPV infection can be removed naturally by the host immune response and only a small percentage may progress to cancer; thus, the immune response is essential for the control of precursor lesions and CC. We present a review of recent research on the molecular mechanisms that allow HPV-infected cells to evade immune surveillance and potential targets of molecular therapy to inhibit tumor immune escape
Chaotic Waveguide-Based Resonators for Microlasers
We propose the construction of highly directional emission microlasers using
two-dimensional high-index semiconductor waveguides as {\it open} resonators.
The prototype waveguide is formed by two collinear leads connected to a cavity
of certain shape. The proposed lasing mechanism requires that the shape of the
cavity yield mixed chaotic ray dynamics so as to have the appropiate (phase
space) resonance islands. These islands allow, via Heisenberg's uncertainty
principle, the appearance of quasi bound states (QBS) which, in turn,
propitiate the lasing mechanism. The energy values of the QBS are found through
the solution of the Helmholtz equation. We use classical ray dynamics to
predict the direction and intensity of the lasing produced by such open
resonators for typical values of the index of refraction.Comment: 5 pages, 5 figure
Effect of Yb concentration on the resistivity and lifetime of CdTe:Ge:Yb codoped crystals
The resistivity and electron lifetime of CdTe:Ge:Yb crystals are reported, demonstrating that the
effect of Yb concentration is crucial for accurate electrical compensation. It is also demonstrated
that the codoping of CdTe with Ge as deep donor and with Yb as rare-earth element could be a
promising way to obtain semiinsulating CdTe crystals with good transport properties. High
resistivity 5 10
9
cm and lifetime 9 s were obtained, thus confirming the beneficial effect of
rare-earth dopingThis work has been partly supported by the projects
CAM SENSORCDT S-0505/MAT/0209, CAM FOTOFLEX S-0505/ENE-123, and EU FP6 PHOLOGIC 017158. E.S.
also acknowledges the Spanish MEC for the fellowship FPU
2003-1388.Peer reviewe
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