3,877 research outputs found
The Semiclassical Coulomb Interaction
The semiclassical Coulomb excitation interaction is at times expressed in the
Lorentz gauge in terms of the electromagnetic fields and a contribution from
the scalar electric potential. We point out that the potential term can make
spurious contributions to excitation cross sections, especially when the the
decay of excited states is taken into account. We show that, through an
appropriate gauge transformation, the excitation interaction can be expressed
in terms of the electromagnetic fields alone.Comment: 12 pages. Phys. Rev. C, Rapid Communication, in pres
Role of virtual break-up of projectile in astrophysical fusion reactions
We study the effect of virtual Coulomb break-up, commonly known as the dipole
polarizability, of the deuteron projectile on the astrophysical fusion reaction
3He(d,p)4He. We use the adiabatic approximation to estimate the potential shift
due to the E1 transition to the continuum states in the deuteron, and compute
the barrier penetrability in the WKB approximation. We find that the
enhancement of the penetrability due to the deuteron break-up is too small to
resolve the longstanding puzzle observed in laboratory measurements that the
electron screening effect is surprisingly larger than theoretical prediction
based on an atomic physics model. The effect of the 3He break-up in the
3He(d,p)4He reaction, as well as the 7Li break-up in the 7Li(p,alpha)4He
reaction is also discussed.Comment: 9 pages, 2 eps figure
Matrix Elements of Random Operators and Discrete Symmetry Breaking in Nuclei
It is shown that several effects are responsible for deviations of the
intensity distributions from the Porter-Thomas law. Among these are genuine
symmetry breaking, such as isospin; the nature of the transition operator;
truncation of the Hilbert space in shell model calculations and missing
transitionsComment: 8 pages, 3 figure
An attempt to understand complexity in a government digital transformation project
Digital transformation projects will become one of the dominating tools for mastering digital transformation in governments. Studies show that such projects are complex undertakings and increasingly difficult to manage. The purpose of the paper is to provide a better understanding of the factors that cause complexity in government digital transformation projects. The authors use an in-depth case study approach to investigate factors of complexity in an ongoing digital transformation project. The results indicate that complexity in this project is rooted in dynamic relationships between multiple dimensions of organization, technologies, and innovation. The authors conclude that when organizational structuring, the introduction of new technology, and efforts to innovate and create added value for citizens and businesses operate in tandem, the pervasive complexity associated with delivering government digital transformation projects becomes increasingly difficult to manage
SiGe Raman spectra vs. local clustering/anticlustering : Percolation scheme and ab initio calculations
We formalize within the percolation scheme, that operates along the linear
chain approximation, namely at one dimension (1D), an intrinsic ability behind
Raman scattering to achieve a quantitative insight into local clustering or
anticlustering in an alloy, using SiGe as a case study. For doing so, we derive
general expressions of the individual fractions of the six SiGe
percolation-type oscillators [1(Ge-Ge), 3(Si-Ge), 2(Si-Si)], which monitor
directly the Raman intensities, via a relevant order parameter k. This is
introduced by adapting to the 1D oscillators of the SiGe diamond version of the
1D percolation scheme, namely along a fully consistent 1D treatment, the
approach originally used by Verleur and Barker for the three-dimensional (3D)
oscillators of their 1D cluster scheme applying to zincblende alloys [H.W.
Verleur and A.S. Barker, Phys. Rev. 149, 715 (1966)], a somehow problematic one
in fact, due to its 3D vs. 1D ambivalence. Predictive k-dependent intensity
interplays between the SiGe (50 at.%Si) Raman lines are confronted with
existing experimental data and with ab initio Raman spectra obtained by using
large (32 atom) disordered supercells matching the required k values, with
special attention to the Si-Ge triplet and to the Si-Si doublet, respectively.Comment: 20 pages, 6 figure
Network Mutual Information and Synchronization under Time Transformations
We investigate the effect of general time transformations on the phase
synchronization (PS) phenomenon and the mutual information rate (MIR) between
pairs of nodes in dynamical networks. We demonstrate two important results
concerning the invariance of both PS and the MIR. Under time transformations PS
can neither be introduced nor destroyed and the MIR cannot be raised from zero.
On the other hand, for proper time transformations the timing between the
cycles of the coupled oscillators can be largely improved. Finally, we discuss
the relevance of our findings for communication in dynamical networks.Comment: 15 p
Piecewise constant potentials and discrete ambiguities
This work is devoted to the study of discrete ambiguities. For parametrized
potentials, they arise when the parameters are fitted to a finite number of
phase-shifts. It generates phase equivalent potentials. Such equivalence was
suggested to be due to the modulo uncertainty inherent to phase
determinations. We show that a different class of phase-equivalent potentials
exists. To this aim, use is made of piecewise constant potentials, the
intervals of which are defined by the zeros of their regular solutions of the
Schr\"odinger equation. We give a classification of the ambiguities in terms of
indices which include the difference between exact phase modulo and the
numbering of the wave function zeros.Comment: 26 pages Subject: Mathematical Physics math-p
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