289 research outputs found
Using Local Context To Improve Face Detection
Most face detection algorithms locate faces by classifying the content of a detection window iterating over all positions and scales of the input image. Recent developments have accelerated this process up to real-time performance at high levels of accuracy. However, even the best of today's computational systems are far from being able to compete with the detection capabilities of the human visual system. Psychophysical experiments have shown the importance of local context in the face detection process. In this paper we investigate the role of local context for face detection algorithms. In experiments on two large data sets we find that using local context can significantly increase the number of correct detections, particularly in low resolution cases, uncommon poses or individual appearances as well as occlusions
Complex energy approaches for calculating isobaric analogue states
Two methods the complex energy shell model (CXSM) and the complex scaling
(CS) approach were used for calculating isobaric analog resonances (IAR) in the
Lane model. The IAR parameters calculated by the CXSM and the CS methods were
checked against the parameters extracted from the direct numerical solution of
the coupled channel Lane equations (CC). The agreement with the CC results was
generally better than 1 keV for both methods and for each partial waves
concerned. Similarities and differences of the CXSM and the CS methods are
discussed. CXSM offers a direct way to study the configurations of the IAR wave
function in contrast to the CS method.Comment: 3 figure
Localization of shadow poles by complex scaling
Through numerical examples we show that the complex scaling method is suited
to explore the pole structure in multichannel scattering problems. All poles
lying on the multisheeted Riemann energy surface, including shadow poles, can
be revealed and the Riemann sheets on which they reside can be identified.Comment: 6 pages, Latex with Revtex, 3 figures (not included) available on
reques
Shell Corrections for Finite-Depth Deformed Potentials: Green's Function Oscillator Expansion Method
Shell corrections of the finite deformed Woods-Saxon potential are calculated
using the Green's function method and the generalized Strutinsky smoothing
procedure. They are compared with the results of the standard prescription
which are affected by the spurious contribution from the unphysical particle
gas. In the new method, the shell correction approaches the exact limit
provided that the dimension of the single-particle (harmonic oscillator) basis
is sufficiently large. For spherical potentials, the present method is faster
than the exact one in which the contribution from the particle continuum states
is explicitly calculated. For deformed potentials, the Green's function method
offers a practical and reliable way of calculating shell corrections for weakly
bound nuclei.Comment: submitted to Phys. Rev. C, 12 pages, 7 figure
Modified two-potential approach to tunneling problems
One-body quantum tunneling to continuum is treated via the two-potential
approach, dividing the tunneling potential into external and internal parts. We
show that corrections to this approach can be minimized by taking the
separation radius inside the interval determined by simple expressions. The
resulting two-potential approach reproduces the resonance energy and its width,
both for narrow and wide resonances. We also demonstrate that, without losing
its accuracy, the two-potential approach can be modified to a form resembling
the R-matrix theory, yet without any uncertainties of the latter related to the
choice of the matching radius.Comment: 7 two-column pages, 3 figures, extra-explanation added, Phys. Rev. A,
in pres
Continued fraction representation of the Coulomb Green's operator and unified description of bound, resonant and scattering states
If a quantum mechanical Hamiltonian has an infinite symmetric tridiagonal
(Jacobi) matrix form in some discrete Hilbert-space basis representation, then
its Green's operator can be constructed in terms of a continued fraction. As an
illustrative example we discuss the Coulomb Green's operator in
Coulomb-Sturmian basis representation. Based on this representation, a quantum
mechanical approximation method for solving Lippmann-Schwinger integral
equations can be established, which is equally applicable for bound-, resonant-
and scattering-state problems with free and Coulombic asymptotics as well. The
performance of this technique is illustrated with a detailed investigation of a
nuclear potential describing the interaction of two particles.Comment: 7 pages, 4 ps figures, revised versio
Theoretical description of deformed proton emitters: nonadiabatic coupled-channel method
The newly developed nonadiabatic method based on the coupled-channel
Schroedinger equation with Gamow states is used to study the phenomenon of
proton radioactivity. The new method, adopting the weak coupling regime of the
particle-plus-rotor model, allows for the inclusion of excitations in the
daughter nucleus. This can lead to rather different predictions for lifetimes
and branching ratios as compared to the standard adiabatic approximation
corresponding to the strong coupling scheme. Calculations are performed for
several experimentally seen, non-spherical nuclei beyond the proton dripline.
By comparing theory and experiment, we are able to characterize the angular
momentum content of the observed narrow resonance.Comment: 12 pages including 10 figure
Three-body resonances in He-6, Li-6, and Be-6, and the soft dipole mode problem of neutron halo nuclei
Using the complex scaling method, the low-lying three-body resonances of
He, Li, and Be are investigated in a parameter-free microscopic
three-cluster model. In He a 2, in Li a 2 and a 1, and in
Be the 0 ground state and a 2 excited state is found. The other
experimentally known 2 state of Li cannot be localized by our present
method. We have found no indication for the existence of the predicted 1
soft dipole state in He. We argue that the sequential decay mode of He
through the resonant states of its two-body subsystem can lead to peaks in the
excitation function. This process can explain the experimental results in the
case of Li, too. We propose an experimental analysis, which can decide
between the soft dipole mode and the sequential decay mode.Comment: REVTEX, Submitted to Phys. Rev. C, 12 pages, 2 postscript figures are
available upon request. CALTECH, MAP-16
Comment on ``Large-space shell-model calculations for light nuclei''
In a recent publication Zheng, Vary, and Barrett reproduced the negative
quadrupole moment of Li-6 and the low-lying positive-parity states of He-5 by
using a no-core shell model. In this Comment we question the meaning of these
results by pointing out that the model used is inadequate for the reproduction
of these properties.Comment: Latex with Revtex, 1 postscript figure in separate fil
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