28,018 research outputs found
Analyses of celestial pole offsets with VLBI, LLR, and optical observations
This work aims to explore the possibilities of determining the long-period
part of the precession-nutation of the Earth with techniques other than very
long baseline interferometry (VLBI). Lunar laser ranging (LLR) is chosen for
its relatively high accuracy and long period. Results of previous studies could
be updated using the latest data with generally higher quality, which would
also add ten years to the total time span. Historical optical data are also
analyzed for their rather long time-coverage to determine whether it is
possible to improve the current Earth precession-nutation model
Probing The Neutrino Sector via A Statistical Approach
We apply the idea of landscape (motivated by string theory) to study the
statistical nature of parameters/couplings in the standard model of strong and
electroweak interactions. Following the success of this approach on the fermion
masses, we discuss the divergent behavior of the probability distributions of
other physical parameters/couplings to obtain some insights on the quantities
that cannot be measured by current experiments but can be relevant in
cosmology, in particular those in the neutrino sector. From a relatively
strongly mixed PMNS matrix, we argue that the probability distribution of heavy
neutrino mass does not diverge at . This analysis favors the
degenerate heavy neutrino scenarios.Comment: 29 pages,7 figure
Observation of recoil-induced resonances and electromagnetically induced absorption of cold atoms in diffuse light
In this paper we report an experiment on the observation of the
recoil-induced resonances (RIR) and electromagnetically induced absorption
(EIA) of cold Rb87 atoms in diffuse light. The pump light of the RIR and the
EIA comes from the diffuse light in an integrating sphere, which also serves
the cooling light. The probe light beam is a weak laser split from the cooling
laser in order to keep the cooling and probe lasers correlated. We measured the
RIR and the EIA signal varying with the detuning of the diffuse laser light,
and also measured the temperature of the cold atoms at the different detunings.
The mechanism of RIR and EIA in the configuration with diffuse-light pumping
and laser probing is discussed, and the difference of nonlinear spectra of cold
atoms between in diffuse-light cooling system and in optical molasses as well
as in a magneto-optical trap (MOT) are studied.Comment: 9 pages, 6 figure
Asymptotic correlation functions and FFLO signature for the one-dimensional attractive Hubbard model
We study the long-distance asymptotic behavior of various correlation
functions for the one-dimensional (1D) attractive Hubbard model in a partially
polarized phase through the Bethe ansatz and conformal field theory approaches.
We particularly find the oscillating behavior of these correlation functions
with spatial power-law decay, of which the pair (spin) correlation function
oscillates with a frequency (). Here is the mismatch in the Fermi surfaces of
spin-up and spin-down particles. Consequently, the pair correlation function in
momentum space has peaks at the mismatch , which has been
observed in recent numerical work on this model. These singular peaks in
momentum space together with the spatial oscillation suggest an analog of the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state in the 1D Hubbard model. The
parameter representing the lattice effect becomes prominent in critical
exponents which determine the power-law decay of all correlation functions. We
point out that the backscattering of unpaired fermions and bound pairs within
their own Fermi points gives a microscopic origin of the FFLO pairing in 1D.Comment: 26 pages, 4 figures, published version, a series of study on the 1D
attractive Hubbard model, few typos were corrected, references were added,
also see arXiv:1708.07784 and arXiv:1708.0777
Safety Grade Evaluation of Aqueduct Structure Based on Fuzzy Cloud Theory Analysis
In view of the limitation of natural conversion between qualitative concept and quantitative value, the fuzzy analysis method cannot be employed to improve the multi-stage fuzzy evaluation method. Improvement of multilevel fuzzy evaluation method based on cloud theory was found, which could comprehensively consider the uncertainty of random combinations and the fuzziness of interaction between influencing factors, and the shortcomings of conventional fuzzy evaluation methods as well eliminated. The structure of 5#U-aqueduct in Jingdian Irrigation District (Gansu, China) was chosen as the research object. Based on the multi-level fuzzy evaluation index system of structural safety, experts were invited to score the importance of factors according to the cloud theory scale criterion to establish a judgment matrix. Therefore, the evaluation set, weight and membership cloud model of evaluation system was constituted by means of bridge safety assessment criterion and cloud generator principle. Furthermore, comprehensive evaluation results of aqueduct service states were obtained by multistage fuzzy composite mapping method, and the actual position of structural safety grade was obtained by comparing the evaluation result with the comment layer cloud drop diagram. The results showed that using cloud model parameters (Ex, En and He) to describe the relative importance of factors can better reflect the randomness and fuzziness of each other than the traditional single number, which was helpful to get the evaluation results accurately and objectively; The comprehensive evaluation results of the aqueduct structure obtained by calculation were WV(75.149, 9.95, 4.16).The simulated cloud droplet diagram was located between II and III classes, and tends to the III standard, which indicated that the overall security of the structure was sufferable. However, attention should be paid to the maintenance and repair of the detailed components. The consequences agreed with the evaluation results of the experts, which indicates that the improved evaluation method has good practicability as well as can be popularized and applied
The Effect of Product Recommendations on Online Investor Behaviors
Despite the popularity of product recommendations on online investment
platforms, few studies have explored their impact on investor behaviors. Using
data from a global e-commerce platform, we apply regression discontinuity
design to causally examine the effects of product recommendations on online
investors' mutual fund investments. Our findings indicate that recommended
funds experience a significant rise in purchases, especially among low
socioeconomic status investors who are most influenced by these
recommendations. However, investors tend to suffer significantly worse
investment returns after purchasing recommended funds, and this negative impact
is also most significant for investors with low socioeconomic status. To
explain this disparity, we find investors tend to gather less information and
expend reduced effort in fund research when buying recommended funds.
Furthermore, investors' redemption timing of recommended funds is less optimal
than non-recommended funds. We also find that recommended funds experience a
larger return reversal than non-recommended funds. In conclusion, product
recommendations make investors behave more irrationally and these negative
consequences are most significant for investors with low socioeconomic status,
which can amplify wealth inequality among investors in financial markets
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