1,420 research outputs found
Disorder effects on the quantum coherence of a many-boson system
The effects of disorders on the quantum coherence for many-bosons are studied
in a double well model. For the ground state, the disorder enhances the quantum
coherence. In the deep Mott regime, dynamical evolution reveals periodical
collapses and revivals of the quantum coherence which is robust against the
disorder. The average over variations in both the on-site energy and the
interaction reveals a beat phenomenon of the coherence-decoherence oscillation
in the temporal evolution.Comment: 4 figure
Statistical distribution of HI 21cm intervening absorbers as potential cosmic acceleration probes
Damped Lyman- Absorber (DLA), or HI 21cm Absorber (H21A), is an
important probe to model-independently measure the acceleration of
spectroscopic velocity () via the Sandage-Loeb (SL) effect.
Confined by the shortage of DLAs and Background Radio Sources (BRSs) with
adequate information, the detectable amount of DLAs is ambiguous in the bulk of
previous work. After differing the acceleration of scale factor ()
from the first order time derivative of spectroscopic velocity
(), we make a statistical investigation of the amount of
potential DLAs in the most of this paper. Using Kernel Density Estimation (KDE)
to depict general redshift distributions of BRSs, observed DLAs and a DLA
detection rate with different limitations (1.4GHz flux, HI column density and
spin temperature), we provide fitted multi-Gaussian expressions of the three
components and their 1 regions by bootstrap, with a proportional
constant of H21As in detected DLAs, leading to the measurable number
predictions of H21As for FAST, ASKAP and SKA1-Mid in HI absorption blind
survey. In our most optimistic condition (>10mJy,
and >500K), the
FAST, AKSAP and SKA1-Mid would probe about 80, 500 and 600 H21As respectively.Comment: Accepted by MNRAS, 11 pages(without references), 20 figures, 6 table
The strong vertices of charmed mesons , and charmonia ,
In this work, the strong form factors and coupling constants of the vertices
, , , ,
are calculated within the framework of the QCD sum rule.
For each vertex, we analyze the form factor considering all possible off-shell
cases and the contributions of the vacuum condensate terms
, ,
, and
. Then, the form
factors are fitted into analytical functions and are extrapolated into
time-like regions to get the strong coupling constants. Finally, the strong
coupling constants are obtained by using on-shell cases of the intermediate
mesons(). The results are as follows,
,
GeV,
,
and
GeV
Dynamic response of a pavement-subgrade-soft ground system subjected to moving traffic load
This paper introduces a three-dimensional model for the steady-state response of a pavement-subgrade-soft ground system subjected to moving traffic load. A semi-analytical wave propagation model is introduced which is subjected to four rectangular moving loads and based on a calculation method of the dynamic stiffness matrix of the ground. In order to model a complete road system, the effect of a simple road model is taken into account including pavement, subgrade and soft subsoil. The pavement and the subgrade are regarded as two elastic layers resting on a poroelastic half-space soil medium. The priority has been given to a simple formulation based on the principle of spatial Fourier transforms compatible with good numerical efficiency and yet providing quick solutions. The frequency wave-number domain solution of the road system is obtained by the compatibility condition at the interface of the structural layers. By introducing FFT (Fast Fourier Transform) algorithm, the numerical results are derived and the influences of the observation coordinates, the load speed and excitation frequency, the permeability of the soft subsoil, and the rigidity of the subgrade on the response of the pavement-subgrade-soft ground system are investigated. The numerical results show that the influences of these parameters on the dynamic response of the road system are significant
The strong vertices of bottom mesons , and bottomonia ,
In this article, the strong coupling constants of vertices ,
, , and
are analyzed in the framework of QCD sum rules. In this
work, all possible off-shell cases and the contributions of vacuum condensate
terms including , , , and
are considered. The
momentum dependent strong coupling constants are first calculated and then are
fitted into analytical functions which are used to extrapolate into
time-like regions to obtain the final values of strong coupling constants. The
final results are ,
GeV,
,
and
GeV. These strong
coupling constants are important input parameters which reflect the dynamic
properties of the interactions among the mesons and quarkonia
Analysis of the strong vertices of and in QCD sum rules
In this work, we analyze the strong vertices and
using the three-point QCD sum rules under the tensor
structures ,
and . We firstly calculate the momentum
dependent strong coupling constants by considering contributions of
the perturbative part and the condensate terms ,
, and
. By fitting these coupling constants into
analytical functions and extrapolating them into time-like regions, we then
obtain the on-shell values of strong coupling constants for these vertices. The
results are GeV,
GeV,
GeV,
GeV,
GeV and
GeV. These strong
coupling constants are important parameters which can help us to understand the
strong decay behaviors of hadrons
Modification of Transition-Metal Redox by Interstitial Water in Hexacyanometalate Electrodes for Sodium-Ion Batteries.
A sodium-ion battery (SIB) solution is attractive for grid-scale electrical energy storage. Low-cost hexacyanometalate is a promising electrode material for SIBs because of its easy synthesis and open framework. Most hexacyanometalate-based SIBs work with aqueous electrolyte, and interstitial water in the material has been found to strongly affect the electrochemical profile, but the mechanism remains elusive. Here we provide a comparative study of the transition-metal redox in hexacyanometalate electrodes with and without interstitial water based on soft X-ray absorption spectroscopy and theoretical calculations. We found distinct transition-metal redox sequences in hydrated and anhydrated NaxMnFe(CN)6Β·zH2O. The Fe and Mn redox in hydrated electrodes are separated and are at different potentials, leading to two voltage plateaus. On the contrary, mixed Fe and Mn redox in the same potential range is found in the anhydrated system. This work reveals for the first time how transition-metal redox in batteries is strongly affected by interstitial molecules that are seemingly spectators. The results suggest a fundamental mechanism based on three competing factors that determine the transition-metal redox potentials. Because most hexacyanometalate electrodes contain water, this work directly reveals the mechanism of how interstitial molecules could define the electrochemical profile, especially for electrodes based on transition-metal redox with well-defined spin states
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