10,082 research outputs found
Uncertainties in Dielectronic Recombination Rate Coefficients: Effects on Solar and Stellar Upper Atmosphere Abundance Determinations
We have investigated how the relative elemental abundances inferred from the
solar upper atmosphere are affected by uncertainties in the dielectronic
recombination (DR) rate coefficients used to analyze the spectra. We find that
the inferred relative abundances can be up to a factor of ~5 smaller or ~1.6
times larger than those inferred using the currently recommended DR rate
coefficients. We have also found a plausible set of variations to the DR rate
coefficients which improve the inferred (and expected) isothermal nature of
solar coronal observations at heights of >~ 50 arcsec off the solar limb. Our
results can be used to help prioritize the enormous amount of DR data needed
for modeling solar and stellar upper atmospheres. Based on the work here, our
list of needed rate coefficients for DR onto specific isoelectronic sequences
reads, in decreasing order of importance, as follows: O-like, C-like, Be-like,
N-like, B-like, F-like, Li-like, He-like, and Ne-like. It is our hope that this
work will help to motivate and prioritize future experimental and theoretical
studies of DR.Comment: 33 pages, including 3 figures and 4 tables. To be published in Ap
Nonlinear Breathing-like Localized Modes in C60 Nanocrystals
We study the dynamics of nanocrystals composed of C60 fullerene molecules. We
demonstrate that such structures can support long-lived strongly localized
nonlinear oscillatory modes, which resemble discrete breathers in simple
lattices. We reveal that at room temperatures the lifetime of such nonlinear
localized modes may exceed tens of picoseconds; this suggests that C60
nanoclusters should demonstrate anomalously slow thermal relaxation when the
temperature gradient decays in accord to a power law, thus violating the
Cattaneo-Vernotte law of thermal conductivity.Comment: 6 pages, 6 figure
Statistics of conductance and shot-noise power for chaotic cavities
We report on an analytical study of the statistics of conductance, , and
shot-noise power, , for a chaotic cavity with arbitrary numbers of
channels in two leads and symmetry parameter . With the theory
of Selberg's integral the first four cumulants of and first two cumulants
of are calculated explicitly. We give analytical expressions for the
conductance and shot-noise distributions and determine their exact asymptotics
near the edges up to linear order in distances from the edges. For a
power law for the conductance distribution is exact. All results are also
consistent with numerical simulations.Comment: 7 pages, 3 figures. Proc. of the 3rd Workshop on Quantum Chaos and
Localisation Phenomena, Warsaw, Poland, May 25-27, 200
Lie algebra and invariant tensor technology for g2
Proceeding in analogy with su(n) work on lambda matrices and f- and
d-tensors, this paper develops the technology of the Lie algebra g2, its seven
dimensional defining representation gamma and the full set of invariant tensors
that arise in relation thereto. A comprehensive listing of identities involving
these tensors is given. This includes identities that depend on use of
characteristic equations, especially for gamma, and a good body of results
involving the quadratic, sextic and (the non-primitivity of) other Casimir
operators of g2.Comment: 29 pages, LaTe
Heat Conduction in One-Dimensional chain of Hard Discs with Substrate Potential
Heat conduction of one-dimensional chain of equivalent rigid particles in the
field of external on-site potential is considered. Zero diameters of the
particles correspond to exactly integrable case with divergent heat conduction
coefficient. By means of simple analytical model it is demonstrated that for
any nonzero particle size the integrability is violated and the heat conduction
coefficient converges. The result of the analytical computation is verified by
means of numerical simulation in a plausible diapason of parameters and good
agreement is observedComment: 14 pages, 7 figure
Properties of short-range and long-range correlation energy density functionals from electron-electron coalescence
The combination of density functional theory with other approaches to the
many-electron problem through the separation of the electron-electron
interaction into a short-range and a long-range contribution is a promising
method, which is raising more and more interest in recent years. In this work
some properties of the corresponding correlation energy functionals are derived
by studying the electron-electron coalescence condition for a modified
(long-range-only) interaction. A general relation for the on-top (zero
electron-electron distance) pair density is derived, and its usefulness is
discussed with some examples. For the special case of the uniform electron gas,
a simple parameterization of the on-top pair density for a long-range only
interaction is presented and supported by calculations within the ``extended
Overhauser model''. The results of this work can be used to build
self-interaction corrected short-range correlation energy functionals.Comment: revised version, to appear in Phys. Rev.
Correlation functions of impedance and scattering matrix elements in chaotic absorbing cavities
Wave scattering in chaotic systems with a uniform energy loss (absorption) is
considered. Within the random matrix approach we calculate exactly the energy
correlation functions of different matrix elements of impedance or scattering
matrices for systems with preserved or broken time-reversal symmetry. The
obtained results are valid at any number of arbitrary open scattering channels
and arbitrary absorption. Elastic enhancement factors (defined through the
ratio of the corresponding variance in reflection to that in transmission) are
also discussed.Comment: 10 pages, 2 figures (misprints corrected and references updated in
ver.2); to appear in Acta Phys. Pol. A (Proceedings of the 2nd Workshop on
Quantum Chaos and Localization Phenomena, May 19-22, 2005, Warsaw
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