5,148 research outputs found
Quantum phase transition and entanglement in Li atom system
In this paper we study the quantum phase transition and entanglement in
s1=1/2 and s2=1 spin pair system by the exact diagonalization method. We show
that, for this exactly solvable quantum bi-spin system, entanglement appears
before quantum phase transition and disappears after it. Moreover, we show that
the von Neumann entropy, as a measure of entanglement, can reveal quantum phase
transition in this system.Comment: 5 pages, 2 figure
Ensemble Methods for Personalized E-Commerce Search Challenge at CIKM Cup 2016
Personalized search has been a hot research topic for many years and has been
widely used in e-commerce. This paper describes our solution to tackle the
challenge of personalized e-commerce search at CIKM Cup 2016. The goal of this
competition is to predict search relevance and re-rank the result items in SERP
according to the personalized search, browsing and purchasing preferences.
Based on a detailed analysis of the provided data, we extract three different
types of features, i.e., statistic features, query-item features and session
features. Different models are used on these features, including logistic
regression, gradient boosted decision trees, rank svm and a novel deep match
model. With the blending of multiple models, a stacking ensemble model is built
to integrate the output of individual models and produce a more accurate
prediction result. Based on these efforts, our solution won the champion of the
competition on all the evaluation metrics.Comment: First Place Solution at CIKM Cup 2016 Track
Solar Flares with an Exponential Growth of the Emission Measure in the Impulsive Phase Derived from X-ray Observations
The light curves of solar flares in the impulsive phase are complex in
general, indicating that multiple physical processes are involved in. With the
GOES (Geostationary Operational Environmental Satellite) observations, we find
that there are a subset of flares, whose impulsive phases are dominated by a
period of exponential growth of the emission measure. The flares occurred from
January 1999 to December 2002 are analyzed, and the results from the
observations made with both GOES 8 and GEOS 10 satellites are compared to
estimate the instrumental uncertainties. Their mean temperatures during this
exponential growth phase have a normal distribution. Most flares within the
1\sigma\ range of this temperature distribution belong to the GOES class B or
C, with the peak fluxes at the GOES low-energy channel following a log-normal
distribution. The growth rate and duration of the exponential growth phase also
follow a lognormal distribution, in which the duration is distributed in the
range from half a minute to about half an hour. As expected, the growth time is
correlated with the decay time of the soft X-ray flux. We also find that the
growth rate of the emission measure is strongly anti-correlated with the
duration of the exponential growth phase, and the mean temperature increases
slightly with the increase of the growth rate. The implications of these
results on the study of energy release in solar flares are discussed in the
end.Comment: 10 figure
Session-aware Information Embedding for E-commerce Product Recommendation
Most of the existing recommender systems assume that user's visiting history
can be constantly recorded. However, in recent online services, the user
identification may be usually unknown and only limited online user behaviors
can be used. It is of great importance to model the temporal online user
behaviors and conduct recommendation for the anonymous users. In this paper, we
propose a list-wise deep neural network based architecture to model the limited
user behaviors within each session. To train the model efficiently, we first
design a session embedding method to pre-train a session representation, which
incorporates different kinds of user search behaviors such as clicks and views.
Based on the learnt session representation, we further propose a list-wise
ranking model to generate the recommendation result for each anonymous user
session. We conduct quantitative experiments on a recently published dataset
from an e-commerce company. The evaluation results validate the effectiveness
of the proposed method, which can outperform the state-of-the-art
significantly
Non-symmetry constraints of the AKNS system yielding integrable Hamiltonian systems
This paper aims to show that there exist non-symmetry constraints which yield
integrable Hamiltonian systems through nonlinearization of spectral problems of
soliton systems, like symmetry constraints. Taking the AKNS spectral problem as
an illustrative example, a class of such non-symmetry constraints is introduced
for the AKNS system, along with two-dimensional integrable Hamiltonian systems
generated from the AKNS spectral problem.Comment: latex, 8 pages, to appear in Chaos, Solitons and Fractal
Hamiltonian Structures and Reciprocal Transformations for the -KdV-CH Hierarchy
The -KdV-CH hierarchy is a generalization of the Korteweg-de Vries and
Camassa-Holm hierarchies parametrized by constants. In this paper we
clarify some properties of its multi-Hamiltonian structures, prove the
semisimplicity of the associated bihamiltonian structures and the formula for
their central invariants. By introducing a class of generalized Hamiltonian
structures, we give in a natural way the transformation formulae of the
Hamiltonian structures of the hierarchy under certain reciprocal
transformation, and prove the formulae at the level of its dispersionless
limit. We also consider relations of the associated bihamiltonian structures to
Frobenius manifolds.Comment: 37 page
A finite element method of the self-consistent field theory on general curved surfaces
Block copolymers provide a wonderful platform in studying the soft condensed
matter systems. Many fascinating ordered structures have been discovered in
bulk and confined systems. Among various theories, the self-consistent field
theory (SCFT) has been proven to be a powerful tool for studying the
equilibrium ordered structures. Many numerical methods have been developed to
solve the SCFT model. However, most of these focus on the bulk systems, and
little work on the confined systems, especially on general curved surfaces. In
this work, we developed a linear surface finite element method, which has a
rigorous mathematical theory to guarantee numerical precsion, to study the
self-assembled phases of block copolymers on general curved surfaces based on
the SCFT. Furthermore, to capture the consistent surface for a given
self-assembled pattern, an adaptive approach to optimize the size of the
general curved surface has been proposed. To demonstrate the power of this
approach, we investigate the self-assembled patterns of diblock copolymers on
several distinct curved surfaces, including five closed surfaces and an
unclosed surface. Numerical results illustrate the efficiency of the proposed
method. The obtained ordered structures are consistent with the previous
results on standard surfaces, such as sphere and torus. Certainly, the proposed
numerical framework has the capability of studying the phase behaviors on
general surfaces precisely
The interaction with isospin zero in an extended hidden gauge symmetry approach
The interaction via a or exchange is
constructed within an extended hidden gauge symmetry approach, where the
strange quark is replaced by the charm quark in the flavor space. With
this interaction, a bound state slightly lower than the threshold is generated dynamically in the isospin zero sector by
solving the Bethe-Salpeter equation in the coupled-channel approximation, which
might correspond to the particle announced by many collaborations.
This formulism is also used to study the interaction, and a bound state with isospin zero is generated dynamically, which has no
counterpart listed in the review of the Particle Data Group. Furthermore, the
one-pion exchange between the meson and the is analyzed
precisely, and we do not think the one-pion exchange potential need be
considered when the Bethe-Salpeter equation is solved.Comment: 15 pages, 4 figure, 2 table
Improved Time Domain Method to Measure Near-Field Distribution of Buried-Object
The paper analyses the ground antenna echo using microwave frequency detector
and high speed sampling technology and a new method detecting buried object in
time domain near-field is presented. The method detecting particular reflection
echo frequency of microwave pulse via digital signal processing is to reduce
the false alarm rate. Simulation results show that this method has advantages
of easy identification and high precision.Comment: 8 pages, 5 figure
A GeV source in the direction of Supernova Remnant CTB 37B
Supernova remnants (SNRs) are the most attractive candidates for the
acceleration sites of Galactic cosmic rays. We report the detection of GeV
-ray emission with the Pass 8 events recorded by Fermi Large Area
Telescope (Fermi-LAT) in the vicinity of the shell type SNR CTB 37B that is
likely associated with the TeV ray source HESS J1713-381. The photon
spectrum of CTB 37B is consistent with a power-law with an index of
in the energy range of GeV, and the measured flux
connects smoothly with that of HESS J1713-381 at a few hundred GeV. No
significant spatial extension and time variation are detected. The
multi-wavelength data can be well fitted with either a leptonic model or a
hadronic one. However, parameters of both models suggest more efficient
particle acceleration than typical SNRs. Meanwhile, the X-ray and -ray
spectral properties of CTB 37B show that it is an interesting source bridging
young SNRs dominated by non-thermal emission and old SNRs interacting with
molecular clouds.Comment: 6 pages, 5 figures, 2 tables, published in ApJ, 817, 6
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