4,517 research outputs found
A Semiclassical Approach to Fusion Reactions
The semiclassical method of Alder and Winther is generalized to study fusion
reactions. As an illustration, we evaluate the fusion cross section in a
schematic two-channel calculation. The results are shown to be in good
agreement with those obtained with a quantal Coupled-Channels calculation. We
suggest that in the case of coupling to continuum states this approach may
provide a simpler alternative to the Continuum Discretized Coupled-Channels
method.Comment: 6 pages, 1 figure, invited talk at the International Symposium "A new
era of Nuclear Structure Physics", Niigata, Japan, Nov. 19-22 200
A consistent four-body CDCC model of low-energy reactions: Application to 9Be + 208Pb
We investigate the Be + Pb elastic scattering, breakup and fusion
at energies around the Coulomb barrier. The three processes are described
simultaneously, with identical conditions of calculations. The Be nucleus
is defined in an + n three-body model, using the
hyperspherical coordinate method. We first analyze spectroscopic properties of
Be, and show that the model provides a fairly good description of the
low-lying states. The scattering with Pb is then studied with the
Continuum Discretized Coupled Channel (CDCC) method, where the
+ n continuum is approximated by a discrete number of pseudostates. Optical
potentials for the + Pb and n+ Pb systems are taken
from the literature. We present elastic-scattering and fusion cross sections at
different energies.Comment: 8 pages, 3 figures, Proceedings of the International Conference on
Nucleus-Nucleus Collisions, NN 2015, Catania-Italy. arXiv admin note:
substantial text overlap with arXiv:1410.641
Transverse Isotropy in Identical Particle Scattering
It is pointed out that the cross section for the scattering of identical
charged bosons is isotropic over a broad angular range around 90 degrees when
the Sommerfeld parameter has a critical value, which depends exclusively on the
spin of the particle. A discussion of systems where this phenomenon can be
observed is presented.Comment: 8 pages, RevTeX format, 2 figures (.eps format
Improved WKB approximation for quantum tunneling: Application to heavy ion fusion
In this paper we revisit the one-dimensional tunneling problem. We consider
Kemble's approximation for the transmission coefficient. We show how this
approximation can be extended to above-barrier energies by performing the
analytical continuation of the radial coordinate to the complex plane. We
investigate the validity of this approximation by comparing their predictions
for the cross section and for the barrier distribution with the corresponding
quantum mechanical results. We find that the extended Kemble's approximation
reproduces the results of quantum mechanics with great accuracy.Comment: 8 pages, 6 figures, in press, in European. Phys. Journal A (2017
Causal Classical Theory of Radiation Damping
It is shown how initial conditions can be appropriately defined for the
integration of Lorentz-Dirac equations of motion. The integration is performed
\QTR{it}{forward} in time. The theory is applied to the case of the motion of
an electron in an intense laser pulse, relevant to nonlinear Compton
scattering.Comment: 8 pages, 2 figure
Approximate transmission coefficients in heavy ion fusion
In this paper we revisit the one-dimensional tunnelling problem. We consider
different approximations for the transmission through the Coulomb barrier in
heavy ion collisions at near-barrier energies. First, we discuss approximations
of the barrier shape by functional forms where the transmission coefficient is
known analytically. Then, we consider Kemble's approximation for the
transmission coefficient. We show how this approximation can be extended to
above-barrier energies by performing the analytical continuation of the radial
coordinate to the complex plane. We investigate the validity of the different
approximations considered in this paper by comparing their predictions for
transmission coefficients and cross sections of three heavy ion systems with
the corresponding quantum mechanical results.Comment: 12 pages, 6 figure
A study of local approximation for polarization potentials
We discuss the derivation of an equivalent \textit{l}-independent
polarization potential for use in the optical Schr\"{o}dinger equation that
describes the elastic scattering of heavy ions. Three diffferent methods are
used for this purpose. Application of our theory to the low energy scattering
of the halo nucleus Li from a C target is made. It is found that
the notion of \textit{l}-independent polarization potential has some validity
but can not be a good substitute for the \textit{l}-dependent local equivalent
Feshbach polarization potential.Comment: 8 pages, 4 figure
Minimum-Risk Structured Learning of Video Summarization
© 2017 IEEE. Video summarization is an important multimedia task for applications such as video indexing and retrieval, video surveillance, human-computer interaction and video 'storyboarding'. In this paper, we present a new approach for automatic summarization of video collections that leverages a structured minimum-risk classifier and efficient submodular inference. To test the accuracy of the predicted summaries we utilize a recently-proposed measure (V-JAUNE) that considers both the content and frame order of the original video. Qualitative and quantitative tests over two action video datasets - the ACE and the MSR DailyActivity3D datasets - show that the proposed approach delivers more accurate summaries than the compared minimum-risk and syntactic approaches
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