9,556 research outputs found
Parallels between the dynamics at the noise-perturbed onset of chaos in logistic maps and the dynamics of glass formation
We develop the characterization of the dynamics at the noise-perturbed edge
of chaos in logistic maps in terms of the quantities normally used to describe
glassy properties in structural glass formers. Following the recognition [Phys.
Lett. \textbf{A 328}, 467 (2004)] that the dynamics at this critical attractor
exhibits analogies with that observed in thermal systems close to
vitrification, we determine the modifications that take place with decreasing
noise amplitude in ensemble and time averaged correlations and in diffusivity.
We corroborate explicitly the occurrence of two-step relaxation, aging with its
characteristic scaling property, and subdiffusion and arrest for this system.
We also discuss features that appear to be specific of the map.Comment: Revised version with substantial improvements. Revtex, 8 pages, 11
figure
Weak conditions for interpolation in holomorphic spaces
An analogue of the notion of uniformly separated sequences, expressed in terms of extremal functions, yields a necessary and sufficient condition for interpolation in Lp spaces of holomorphic functions of Paley-Wiener-type when 0 < p \leq 1, of Fock-type when 0 < p \leq 2, and of Bergman-type when 0 < p < \infty. Moreover, if a uniformly discrete sequence has a certain uniform non-uniqueness property with respect to any such Lp space (lt; p < \infty$), then it is an interpolation sequence for that space. The proofs of these results are based on an approximation theorem for subharmonic functions, Beurling's results concerning compactwise limits of sequences, and the description of interpolation sequences in terms of Beurling-type densities. Details are carried out only for Fock spaces, which represent the most difficult case
Deep learning based pulse shape discrimination for germanium detectors
Experiments searching for rare processes like neutrinoless double beta decay
heavily rely on the identification of background events to reduce their
background level and increase their sensitivity. We present a novel machine
learning based method to recognize one of the most abundant classes of
background events in these experiments. By combining a neural network for
feature extraction with a smaller classification network, our method can be
trained with only a small number of labeled events. To validate our method, we
use signals from a broad-energy germanium detector irradiated with a Th
gamma source. We find that it matches the performance of state-of-the-art
algorithms commonly used for this detector type. However, it requires less
tuning and calibration and shows potential to identify certain types of
background events missed by other methods.Comment: Published in Eur. Phys. J. C. 9 pages, 10 figures, 3 table
Control of gradient-driven instabilities using shear Alfv\'en beat waves
A new technique for manipulation and control of gradient-driven instabilities
through nonlinear interaction with Alfv\'en waves in a laboratory plasma is
presented. A narrow field-aligned density depletion is created in the Large
Plasma Device (LAPD), resulting in coherent unstable fluctuations on the
periphery of the depletion. Two independent kinetic Alfv\'en waves are launched
along the depletion at separate frequencies, creating a nonlinear beat-wave
response at or near the frequency of the original instability. When the
beat-wave has sufficient amplitude, the original unstable mode is suppressed,
leaving only the beat-wave response at a different frequency, generally at
lower amplitude.Comment: Submitted for Publication in Physical Review Letters. Revision 2
reflects changes suggested by referees for PRL submission. One figure
removed, several major changes to another figure, and a number of major and
minor changes to the tex
Sierpinski signal generates spectra
We investigate the row sum of the binary pattern generated by the Sierpinski
automaton: Interpreted as a time series we calculate the power spectrum of this
Sierpinski signal analytically and obtain a unique rugged fine structure with
underlying power law decay with an exponent of approximately 1.15. Despite the
simplicity of the model, it can serve as a model for spectra in a
certain class of experimental and natural systems like catalytic reactions and
mollusc patterns.Comment: 4 pages (4 figs included). Accepted for publication in Physical
Review
Yield Strength Increase of Cold Formed Sections Due to Cold Work of Forming
The design approach for predicting the increase in yield strength due to cold work of forming in the AISI 1996 Specification for the Design of Cold-Formed Steel Structural members is different from the approach used by the CSA Standard, CSA S136-94, Cold Formed Steel Structural Members. The AISI approach is based on the experimental work conducted by Karren and Winter, while the S136 approach is based on theoretical work by Lind and Schroff. Lind and Schroff used Karren and Winter\u27s data to substantiate their theory. Karren and Winter conducted tests on five full sections and also collected strength data on the flat and corner elements of the same sections, allowing for comparison oftested to calculated values. Twelve different sections were tested as part of the University of Waterloo test program. Strength data was collected on virgin material, full sections and on the flat elements of formed sections, thus permitting comparisons to be made using only experimental data. The main purpose of this investigation was to help answer two questions, Le., 1) should the average yield strength in the flats after forming be allowed in either design approach? and 2) is there a simplified expression that would produce similar results with fewer inputs? Based on the research of this paper, design recommendations were formulated
Trapping and observing single atoms in the dark
A single atom strongly coupled to a cavity mode is stored by
three-dimensional confinement in blue-detuned cavity modes of different
longitudinal and transverse order. The vanishing light intensity at the trap
center reduces the light shift of all atomic energy levels. This is exploited
to detect a single atom by means of a dispersive measurement with 95%
confidence in 0.010 ms, limited by the photon-detection efficiency. As the atom
switches resonant cavity transmission into cavity reflection, the atom can be
detected while scattering about one photon
- …