1,019 research outputs found
Numerical studies of the two- and three-dimensional gauge glass at low temperature
We present results from Monte Carlo simulations of the two- and
three-dimensional gauge glass at low temperature using the parallel tempering
Monte Carlo method. Our results in two dimensions strongly support the
transition being at T_c=0. A finite-size scaling analysis, which works well
only for the larger sizes and lower temperatures, gives the stiffness exponent
theta = -0.39 +/- 0.03. In three dimensions we find theta = 0.27 +/- 0.01,
compatible with recent results from domain wall renormalization group studies.Comment: 7 pages, 10 figures, submitted to PR
Scaling determination of the nonlinear I-V characteristics for 2D superconducting networks
It is shown from computer simulations that the current-voltage (-)
characteristics for the two-dimensional XY model with resistively-shunted
Josephson junction dynamics and Monte Carlo dynamics obeys a finite-size
scaling form from which the nonlinear - exponent can be determined to
good precision. This determination supports the conclusion , where
is the dynamic critical exponent. The results are discussed in the light of the
contrary conclusion reached by Tang and Chen [Phys. Rev. B {\bf 67}, 024508
(2003)] and the possibility of a breakdown of scaling suggested by Bormann
[Phys. Rev. Lett. {\bf 78}, 4324 (1997)].Comment: 6 pages, to appear in PR
Uncertainty-Aware Estimation of Population Abundance using Machine Learning
Machine Learning is widely used for mining collections, such as images, sounds, or texts, by classifying their elements into categories. Automatic classication based on supervised learning requires groundtruth datasets for modeling the elements to classify, and for testing the quality of the classication. Because collecting groundtruth is tedious, a method for estimating the potential errors in large datasets based on limited groundtruth is ne
Adaptive deblurring of surveillance video sequences that deteriorate over time
We present a method for restoring the recordings obtained from surveillance cameras whose quality deteriorates due to dirt or water that gathers on the camera’s lens. The method is designed to operate in the surveillance setting and makes use of good quality frames from the beginning of the recorded sequence to remove the blur at later stages caused by the dirty lens. A background subtraction method allows us to obtain a stable background of the scene. Based on this background, a multiframe blind deconvolution algorithm is used to estimate the Point Spread Function (PSF) of the blur. Once the PSF is obtained it can be used to deblur the entire scene. This restoration method was tested on both synthetic and real data with improvements of 15 dB in PSNR being achieved by using clean frames from the beginning of the recorded sequence
Zero Temperature Glass Transition in the Two-Dimensional Gauge Glass Model
We investigate dynamic scaling properties of the two-dimensional gauge glass
model for the vortex glass phase in superconductors with quenched disorder.
From extensive Monte Carlo simulations we obtain static and dynamic finite
size scaling behavior, where the static simulations use a temperature exchange
method to ensure convergence at low temperatures. Both static and dynamic
scaling of Monte Carlo data is consistent with a glass transition at zero
temperature. We study a dynamic correlation function for the superconducting
order parameter, as well as the phase slip resistance. From the scaling of
these two functions, we find evidence for two distinct diverging correlation
times at the zero temperature glass transition. The longer of these time scales
is associated with phase slip fluctuations across the system that lead to
finite resistance at any finite temperature, while the shorter time scale is
associated with local phase fluctuations.Comment: 8 pages, 10 figures; v2: some minor correction
Competition of Mesoscales and Crossover to Tricriticality in Polymer Solutions
We show that the approach to asymptotic fluctuation-induced critical behavior
in polymer solutions is governed by a competition between a correlation length
diverging at the critical point and an additional mesoscopic length-scale, the
radius of gyration. Accurate light-scattering experiments on polystyrene
solutions in cyclohexane with polymer molecular weights ranging from 200,000 up
to 11.4 million clearly demonstrate a crossover between two universal regimes:
a regime with Ising asymptotic critical behavior, where the correlation length
prevails, and a regime with tricritical theta-point behavior determined by a
mesoscopic polymer-chain length.Comment: 4 pages in RevTeX with 4 figure
Hydrogen-bonded Silica Gels Dispersed in a Smectic Liquid Crystal: A Random Field XY System
The effect on the nematic to smectic-A transition in octylcyanobiphenyl (8CB)
due to dispersions of hydrogen-bonded silica (aerosil) particles is
characterized with high-resolution x-ray scattering. The particles form weak
gels in 8CB creating a quenched disorder that replaces the transition with the
growth of short range smectic correlations. The correlations include thermal
critical fluctuations that dominate at high temperatures and a second
contribution that quantitatively matches the static fluctuations of a random
field system and becomes important at low temperatures.Comment: 10 pages, 4 postscript figures as separate file
- …