26,148 research outputs found
A q-Analog of Dual Sequences with Applications
In the present paper combinatorial identities involving q-dual sequences or
polynomials with coefficients q-dual sequences are derived. Further,
combinatorial identities for q-binomial coefficients(Gaussian coefficients),
q-Stirling numbers and q-Bernoulli numbers and polynomials are deduced.Comment: 14 page
Necessary and sufficient conditions for local creation of quantum discord
We show that a local channel cannot create quantum discord (QD) for zero QD
states of size if and only if either it is a completely decohering
channel or it is a nontrivial isotropic channel. For the qubit case this
propertiy is additionally characteristic to the completely decohering channel
or the commutativity-preserving unital channel. In particular, the exact forms
of the completely decohering channel and the commutativity-preserving unital
qubit channel are proposed. Consequently, our results confirm and improve the
conjecture proposed by X. Hu et al. for the case of and improve the
result proposed by A. Streltsov et al. for the qubit case. Furthermore, it is
shown that a local channel nullifies QD in any state if and only if it is a
completely decohering channel. Based on our results, some protocols of quantum
information processing issues associated with QD, especially for the qubit
case, would be experimentally accessible.Comment: 8 page
Fermi resonance-algebraic model for molecular vibrational spectra
A Fermi resonance-algebraic model is proposed for molecular vibrations, where
a U(2) algebra is used for describing the vibrations of each bond, and Fermi
resonances between stretching and bending modes are taken into account. The
model for a bent molecule XY_2 and a molecule XY_3 is successfully applied to
fit the recently observed vibrational spectrum of the water molecule and arsine
(AsH_3), respectively, and results are compared with those of other models.
Calculations show that algebraic approaches can be used as an effective method
for describing molecular vibrations with small standard deviations
Eruption of a multi-flux-rope system in solar active region 12673 leading to the two largest flares in Solar Cycle 24
Solar active region (AR) 12673 in 2017 September produced two largest flares
in Solar Cycle 24: the X9.3 flare on September 06 and the X8.2 flare on
September 10. We attempt to investigate the evolutions of the two great flares
and their associated complex magnetic system in detail. Aided by the NLFFF
modeling, we identify a double-decker flux rope configuration above the
polarity inversion line (PIL) in the AR core region. The north ends of these
two flux ropes were rooted in a negative- polarity magnetic patch, which began
to move along the PIL and rotate anticlockwise before the X9.3 flare on
September 06. The strong shearing motion and rotation contributed to the
destabilization of the two magnetic flux ropes, of which the upper one
subsequently erupted upward due to the kink-instability. Then another two sets
of twisted loop bundles beside these ropes were disturbed and successively
erupted within 5 minutes like a chain reaction. Similarly, multiple ejecta
components were detected to consecutively erupt during the X8.2 flare occurring
in the same AR on September 10. We examine the evolution of the AR magnetic
fields from September 03 to 06 and find that five dipoles emerged successively
at the east of the main sunspot. The interactions between these dipoles took
place continuously, accompanied by magnetic flux cancellations and strong
shearing motions. In AR 12673, significant flux emergence and successive
interactions between the different emerging dipoles resulted in a complex
magnetic system, accompanied by the formations of multiple flux ropes and
twisted loop bundles. We propose that the eruptions of a multi-flux-rope system
resulted in the two largest flares in Solar Cycle 24.Comment: 10 pages, 8 figures. To be published in A&
Two-component model for the chemical evolution of the Galactic disk
In the present paper, we introduce a two-component model of the Galactic disk
to investigate its chemical evolution. The formation of the thick and thin
disks occur in two main accretion episodes with both infall rates to be
Gaussian. Both the pre-thin and post-thin scenarios for the formation of the
Galactic disk are considered. The best-fitting is obtained through
-test between the models and the new observed metallicity distribution
function of G dwarfs in the solar neighbourhood (Hou et al 1998). Our results
show that post-thin disk scenario for the formation of the Galactic disk should
be preferred. Still, other comparison between model predictions and
observations are given.Comment: 23 pages, 7 figure
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