2,242,745 research outputs found
Study of quadrupole polarizabilities with combined configuration interaction and coupled-cluster method
The recently developed method combining the configuration interaction and the
coupled-cluster method was demonstrated to provide accurate treatment of
correlation corrections in divalent atomic systems [M.S.Safronova, M.G.Kozlov,
and C.W.Clark, Phys. Rev. Lett. 107, 143006 (2011)]. We have extended this
approach to the calculation of quadrupole polarizabilities alpha_2 and applied
it to evaluate alpha_2 for the ground state of Mg and Mg-like Si^{2+}.
Performing the calculations in three different approximations of increasing
accuracy allowed us to place the upper bounds on the uncertainty of the final
results. The recommended values alpha_2(3s^2 1S0)= 35.86(13) a.u. for Si^{2+}
and alpha_2(3s^2 1S0)= 814(3) a.u. for Mg are estimated to be accurate to
0.37%. Differences in quadrupole polarizability contributions in neutral Mg and
Si^{2+} ion are discussed.Comment: 6 pages, submitted to Phys. Rev.
Chaotic behavior of the Compound Nucleus, open Quantum Dots and other nanostructures
It is well established that physical systems exhibit both ordered and chaotic
behavior. The chaotic behavior of nanostructure such as open quantum dots has
been confirmed experimentally and discussed exhaustively theoretically. This is
manifested through random fluctuations in the electronic conductance. What
useful information can be extracted from this noise in the conductance? In this
contribution we shall address this question. In particular, we will show that
the average maxima density in the conductance is directly related to the
correlation function whose characteristic width is a measure of energy- or
applied magnetic field- correlation length. The idea behind the above has been
originally discovered in the context of the atomic nucleus, a mesoscopic
system. Our findings are directly applicable to graphene.Comment: 10 pages, 5 figures. Contribution to: "4th International Workshop on
Compound-Nuclear Reactions and Related Topics (CNR*13)", October 7-11, 2013,
Maresias, Brazil. To appear in the proceeding
Exact diagonalization results for an anharmonically trapped Bose-Einstein condensate
We consider bosonic atoms that rotate in an anharmonic trapping potential.
Using numerical diagonalization of the Hamiltonian, we identify the various
phases of the gas as the rotational frequency of the trap and the coupling
between the atoms are varied.Comment: 7 pages, RevTex, 10 figure
Polarizabilities of Si^{2+}: a benchmark test of theory and experiment
We have calculated electric-dipole polarizabilities of the 3s^2 ^1S_0, 3s3p
^3P_0, and 3s3p ^1P_1 states of the Si^{2+} ion using recently developed
configuration interaction + all-order method. Detailed evaluation of the
uncertainties of the final results is carried out. Our value for the ground
state electric-dipole polarizability 11.670(13) a.u. is in excellent agreement
with the resonant excitation Stark ionization spectroscopy value 11.669(9) a.u.
[Komara et al., J. Phys. B 38, 87 (2005); Mitroy, Phys. Rev. A 78, 052515
(2008)]. This work represents the most precise benchmark test to date of theory
and experiment in divalent atoms. The near cancellation of the ns^2 ^1S_0
ground state and the lowest nsnp ^3P_0 polarizabilities previously observed in
B+, Al+, In+, Tl+, and Pb^{2+} is also found in Si^{2+} ion.Comment: 6 page
Maximal width of the separatrix chaotic layer
The main goal of the paper is to find the {\it absolute maximum} of the width
of the separatrix chaotic layer as function of the frequency of the
time-periodic perturbation of a one-dimensional Hamiltonian system possessing a
separatrix, which is one of the major unsolved problems in the theory of
separatrix chaos. For a given small amplitude of the perturbation, the width is
shown to possess sharp peaks in the range from logarithmically small to
moderate frequencies. These peaks are universal, being the consequence of the
involvement of the nonlinear resonance dynamics into the separatrix chaotic
motion. Developing further the approach introduced in the recent paper by
Soskin et al. ({\it PRE} {\bf 77}, 036221 (2008)), we derive leading-order
asymptotic expressions for the shape of the low-frequency peaks. The maxima of
the peaks, including in particular the {\it absolute maximum} of the width, are
proportional to the perturbation amplitude times either a logarithmically large
factor or a numerical, still typically large, factor, depending on the type of
system. Thus, our theory predicts that the maximal width of the chaotic layer
may be much larger than that predicted by former theories. The theory is
verified in simulations. An application to the facilitation of global chaos
onset is discussed.Comment: 18 pages, 16 figures, submitted to PR
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