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Nonlinear stability of <i>E</i> centers in Si<sub>1-<i>x</i></sub>Ge<sub><i>x</i></sub>: electronic structure calculations
Electronic structure calculations are used to investigate the binding energies of defect pairs composed of lattice vacancies and phosphorus or arsenic atoms (E centers) in silicon-germanium alloys. To describe the local environment surrounding the E center we have generated special quasirandom structures that represent random silicon-germanium alloys. It is predicted that the stability of E centers does not vary linearly with the composition of the silicon-germanium alloy. Interestingly, we predict that the nonlinear behavior does not depend on the donor atom of the E center but only on the host lattice. The impact on diffusion properties is discussed in view of recent experimental and theoretical results
Single chargino production via gluon-gluon fusion in a supersymmetric theory with an explicit R-parity violation
We studied the production of single chargino
accompanied by lepton via gluon-gluon fusion at the LHC. The
numerical analysis of their production rates is carried out in the mSUGRA
scenario with some typical parameter sets. The results show that the cross
sections of the productions via gluon-gluon
collision are in the order of femto barn quantitatively at the
CERN LHC, and can be competitive with production mechanism via quark-antiquark
annihilation process.Comment: LaTex file, 18 pages, 4 EPS file
A three dimensional extinction map of the Galactic Anticentre from multi-band photometry
We present a three dimensional extinction map in band. The map has a
spatial angular resolution, depending on latitude, between 3 -- 9\,arcmin and
covers the entire XSTPS-GAC survey area of over 6,000\, for Galactic
longitude and latitude . By cross-matching the photometric catalog of the Xuyi Schmidt
Telescope Photometric Survey of the Galactic Anticentre (XSTPS-GAC) with those
of 2MASS and WISE, we have built a multi-band photometric stellar sample of
about 30 million stars and applied spectral energy distribution (SED) fitting
to the sample. By combining photometric data from the optical to the
near-infrared, we are able to break the degeneracy between the intrinsic
stellar colours and the amounts of extinction by dust grains for stars with
high photometric accuracy, and trace the extinction as a function of distance
for low Galactic latitude and thus highly extincted regions. This has allowed
us to derive the best-fit extinction and distance information of more than 13
million stars, which are used to construct the three dimensional extinction
map. We have also applied a Rayleigh-Jeans colour excess (RJCE) method to the
data using the 2MASS and WISE colour . The resulting RJCE extinction
map is consistent with the integrated two dimensional map deduced using the
best-fit SED algorithm. However for individual stars, the amounts of extinction
yielded by the RJCE method suffer from larger errors than those given by the
best-fit SED algorithm.Comment: 20 pages, 18 figures, accepted in MNRA
Ranking Spaces for Predicting Human Movement in an Urban Environment
A city can be topologically represented as a connectivity graph, consisting
of nodes representing individual spaces and links if the corresponding spaces
are intersected. It turns out in the space syntax literature that some defined
topological metrics can capture human movement rates in individual spaces. In
other words, the topological metrics are significantly correlated to human
movement rates, and individual spaces can be ranked by the metrics for
predicting human movement. However, this correlation has never been well
justified. In this paper, we study the same issue by applying the weighted
PageRank algorithm to the connectivity graph or space-space topology for
ranking the individual spaces, and find surprisingly that (1) the PageRank
scores are better correlated to human movement rates than the space syntax
metrics, and (2) the underlying space-space topology demonstrates small world
and scale free properties. The findings provide a novel justification as to why
space syntax, or topological analysis in general, can be used to predict human
movement. We further conjecture that this kind of analysis is no more than
predicting a drunkard's walking on a small world and scale free network.
Keywords: Space syntax, topological analysis of networks, small world, scale
free, human movement, and PageRankComment: 11 pages, 5 figures, and 2 tables, English corrections from version 1
to version 2, major changes in the section of introduction from version 2 to
The Nature of Quantum Hall States near the Charge Neutral Dirac Point in Graphene
We investigate the quantum Hall (QH) states near the charge neutral Dirac
point of a high mobility graphene sample in high magnetic fields. We find that
the QH states at filling factors depend only on the perpendicular
component of the field with respect to the graphene plane, indicating them to
be not spin-related. A non-linear magnetic field dependence of the activation
energy gap at filling factor suggests a many-body origin. We therefore
propose that the and states arise from the lifting of the spin
and sub-lattice degeneracy of the LL, respectively.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let
Self-consistent triaxial de Zeeuw-Carollo Models
We use the usual method of Schwarzschild to construct self-consistent
solutions for the triaxial de Zeeuw & Carollo (1996) models with central
density cusps. ZC96 models are triaxial generalisations of spherical
-models of Dehnen whose densities vary as near the center
and at large radii and hence, possess a central density core for
and cusps for . We consider four triaxial models from
ZC96, two prolate triaxials: with and
1.5, and two oblate triaxials: with and
1.5. We compute 4500 orbits in each model for time periods of .
We find that a large fraction of the orbits in each model are stochastic by
means of their nonzero Liapunov exponents. The stochastic orbits in each model
can sustain regular shapes for or longer, which suggests
that they diffuse slowly through their allowed phase-space. Except for the
oblate triaxial models with , our attempts to construct
self-consistent solutions employing only the regular orbits fail for the
remaining three models. However, the self-consistent solutions are found to
exist for all models when the stochastic and regular orbits are treated in the
same way because the mixing-time, , is shorter than the
integration time, . Moreover, the ``fully-mixed'' solutions can
also be constructed for all models when the stochastic orbits are fully mixed
at 15 lowest energy shells. Thus, we conclude that the self-consistent
solutions exist for our selected prolate and oblate triaxial models with
and 1.5.Comment: 6 Pages, 3 Figures, 2 Tables. Accepted for Publication in A&
Systematics of heavy-ion fusion hindrance at extreme sub-barrier energies
The recent discovery of hindrance in heavy-ion induced fusion reactions at
extreme sub-barrier energies represents a challenge for theoretical models.
Previously, it has been shown that in medium-heavy systems, the onset of fusion
hindrance depends strongly on the "stiffness" of the nuclei in the entrance
channel. In this work, we explore its dependence on the total mass and the
-value of the fusing systems and find that the fusion hindrance depends in a
systematic way on the entrance channel properties over a wide range of systems.Comment: Submitted to Phys. Rev. Lett., 5 pages, 3 figure
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