3,451 research outputs found
Collaborative Self-Attention for Recommender Systems
Recommender systems (RS), which have been an essential part in a wide range
of applications, can be formulated as a matrix completion (MC) problem. To
boost the performance of MC, matrix completion with side information, called
inductive matrix completion (IMC), was further proposed. In real applications,
the factorized version of IMC is more favored due to its efficiency of
optimization and implementation. Regarding the factorized version, traditional
IMC method can be interpreted as learning an individual representation for each
feature, which is independent from each other. Moreover, representations for
the same features are shared across all users/items. However, the independent
characteristic for features and shared characteristic for the same features
across all users/items may limit the expressiveness of the model. The
limitation also exists in variants of IMC, such as deep learning based IMC
models. To break the limitation, we generalize recent advances of
self-attention mechanism to IMC and propose a context-aware model called
collaborative self-attention (CSA), which can jointly learn context-aware
representations for features and perform inductive matrix completion process.
Extensive experiments on three large-scale datasets from real RS applications
demonstrate effectiveness of CSA.Comment: There are large modification
Deconfined quantum criticality and emergent SO(5) symmetry in fermionic systems
Deconfined quantum criticality with emergent SO(5) symmetry in correlated
systems remains elusive. Here, by performing numerically-exact state-of-the-art
quantum Monte Carlo (QMC) simulations, we show convincing evidences of
deconfined quantum critical points (DQCP) between antiferromagnetic and
valence-bond-solid phases in the extended Hubbard model of fermions on the
honeycomb lattice with large system sizes. We further demonstrate evidences of
the SO(5) symmetry at the DQCP. It is important to note that the critical
exponents obtained by finite-size scaling at the DQCP here are consistent with
the rigourous conformal bounds. Consequently, we established a promising arena
of DQCP with emergent SO(5) symmetry in interacting systems of fermions. Its
possible experimental relevances in correlated systems of Dirac fermions will
be discussed briefly.Comment: 5.6 pages + Supplemental Materials, 4 figure
Convolutional Geometric Matrix Completion
Geometric matrix completion (GMC) has been proposed for recommendation by
integrating the relationship (link) graphs among users/items into matrix
completion (MC). Traditional GMC methods typically adopt graph regularization
to impose smoothness priors for MC. Recently, geometric deep learning on graphs
(GDLG) is proposed to solve the GMC problem, showing better performance than
existing GMC methods including traditional graph regularization based methods.
To the best of our knowledge, there exists only one GDLG method for GMC, which
is called RMGCNN. RMGCNN combines graph convolutional network (GCN) and
recurrent neural network (RNN) together for GMC. In the original work of
RMGCNN, RMGCNN demonstrates better performance than pure GCN-based method. In
this paper, we propose a new GMC method, called convolutional geometric matrix
completion (CGMC), for recommendation with graphs among users/items. CGMC is a
pure GCN-based method with a newly designed graph convolutional network.
Experimental results on real datasets show that CGMC can outperform other
state-of-the-art methods including RMGCNN in terms of both accuracy and speed
Meson spectrum in Regge phenomenology
Under the assumption that both light and heavy quarkonia populate
approximately linear Regge trajectories with the requirements of additivity of
intercepts and inverse slopes, the masses of different meson multiplets are
estimated. The predictions derived from the quasi-linear Regge trajectories are
in reasonable agreement with those given by many other references.Comment: 21 pages, to appear in Eur. Phys. J.
Fermion-induced quantum critical points
A unified theory of quantum critical points beyond the conventional
Landau-Ginzburg-Wilson paradigm remains unknown. According to Landau cubic
criterion, phase transitions should be first-order when cubic terms of order
parameters are allowed by symmetry in the Landau-Ginzburg free energy. Here,
from renormalization group (RG) analysis we show that second-order quantum
phase transitions can occur at such putatively first-order transitions in
interacting two-dimensional Dirac semimetals. As such type of Landau-forbidden
quantum critical points are induced by gapless fermions, we call them
fermion-induced quantum critical points (FIQCP). We further introduce a
microscopic model of SU(N) fermions on the honeycomb lattice featuring a
transition between Dirac semimetals and Kekule valence bond solids. Remarkably,
our large-scale sign-problem-free Majorana quantum Monte Carlo simulations show
convincing evidences of a FIQCP for N=2,3,4,5,6, consistent with the RG
analysis. We finally discuss possible experimental realizations of the FIQCP in
graphene and graphene-like materials.Comment: Accepted in Nature Communications. Initial submission to a different
journal on Jan. 5th, 2016. The supersymmetry argument is adde
The study of beam loading effect in the CSNS/RCS
CSNS/RCS accelerates a high-intensity proton beam from 80 MeV to 1.6 GeV.
Since the beam current and beam power is high, the beam loading is a severe
problem for the stability of the circulating beam in the RCS. To study the beam
loading effect in the CSNS/RCS theoretically, the RLC circuit model of the rf
cavity, the method of the Fast Fourier Transform and the method of Laplace
transform have been employed to obtain the impedance of the rf system, the beam
spectrum and the beam-induced voltage, respectively. Based on these physical
models, the beam dynamics equations have been revised and a beam loading model
has been constructed in the simulation code ORIENT. By using the code, the beam
loading effect on the rf system of the CSNS/RCS has been investigated. Some
simulation results have been obtained and conclusions have been drawn.Comment: 6 pages, 9 figure
Energy Levels, Transition Rates and Electron Impact Excitation Rates for B-like Kr XXXII
Energy levels and transition rates for electric-dipole, electric-quadrupole,
electric-octupole, magnetic-dipole, and magnetic-quadrupole transitions among
the levels arising from the 5 configurations in B-like Kr XXXII are
calculated by using two state-of-the-art methods, namely, the
multi-configuration Dirac-Hartree-Fock (MCDHF) approach and the second-order
many-body perturbation theory (RMBPT). Our results are compared with several
available experimental and other theoretical values. Electron-impact excitation
(EIE) collision strengths are calculated via the independent process and
isolated resonance approximation using distorted-wave (denoted by IPIRDW).
Radiation damping effects on the resonance excitation contributions are
included. Effective collision strengths are calculated as a function of
electron temperature by assuming a Maxwellian electron velocity distribution.
Spectral line intensities are modeled by using collision radiative model, and
several line pairs pointed out might be useful for density diagnostics
Violation of the viscosity/entropy bound in translationally invariant non-Fermi liquids
The shear viscosity is an important characterization of how a many-body
system behaves like a fluid. We study the shear viscosity in a strongly
interacting solvable model, consisting of coupled Sachdev-Ye-Kitaev (SYK)
islands. As temperature is lowered, the model exhibits a crossover from an
incoherent metal with local criticality to a marginal fermi liquid. We find
that while the ratio of shear viscosity to entropy density in the marginal
Fermi liquid regime satisfies a Kovtun-Son-Starinets (KSS) like bound, it can
strongly violate the KSS bound in a robust temperature range of the incoherent
metal regime, implying a nearly perfect fluidity of the coupled local critical
SYK model. Furthermore, this model also provides the first translationally
invariant example violating the KSS bound with known gauge-gravity
correspondence.Comment: 10 pages, 2 figures; more details added as appendix; and minor
correction
Toward Less Hidden Cost of Code Completion with Acceptance and Ranking Models
Code completion is widely used by software developers to provide coding
suggestions given a partially written code snippet. Apart from the traditional
code completion methods, which only support single token completion at minimal
positions, recent studies show the ability to provide longer code completion at
more flexible positions. However, such frequently triggered and longer
completion results reduce the overall precision as they generate more invalid
results. Moreover, different studies are mostly incompatible with each other.
Thus, it is vital to develop an ensemble framework that can combine results
from multiple models to draw merits and offset defects of each model.
This paper conducts a coding simulation to collect data from code context and
different code completion models and then apply the data in two tasks. First,
we introduce an acceptance model which can dynamically control whether to
display completion results to the developer. It uses simulation features to
predict whether correct results exist in the output of these models. Our best
model reduces the percentage of false-positive completion from 55.09% to
17.44%. Second, we design a fusion ranking scheme that can automatically
identify the priority of the completion results and reorder the candidates from
multiple code completion models. This scheme is flexible in dealing with
various models, regardless of the type or the length of their completion
results. We integrate this ranking scheme with two frequency models and a GPT-2
styled language model, along with the acceptance model to yield 27.80% and
37.64% increase in TOP1 and TOP5 accuracy, respectively. In addition, we
propose a new code completion evaluation metric, Benefit-Cost Ratio(BCR),
taking into account the benefit of keystrokes saving and hidden cost of
completion list browsing, which is closer to real coder experience scenario.Comment: 10 pages, 7 figures, accepted by ICSME 202
Writing and deleting skyrmions with electric fields in a multiferroic heterostructure
Magnetic skyrmions are topological spin textures that can be used as
information carriers for the next-generation information storage and
processing. The electric-field controlling of skyrmions in such devices is
essential but remains technologically challenging. Here, using the
first-principles calculation and the Ginzburg-Landau theory, we propose a
reliable process for writing and deleting skyrmions by electric fields, on the
platform of a multiferroic heterostructure, particularly the
/
heterostructure. We show that the electric field controls the electric
polarization and indirectly influences the antisymmetric Dzyaloshinskii-Moriya
interaction (DMI) between the magnetic moments. The latter is responsible for
the generation and removal of the skyrmion spin textures, and we study this
mechanism by the Ginzburg-Landau analysis. We discuss the real-space Berry
curvature, topological Hall effects, possible quantum anomalous Hall effect,
and other competing magnetic structures. These results represent examples of
quantum technology and may have potential applications in future skyrmionics
and the device fabrication.Comment: 6+epsilon pages, 3 figures, 1 tabl
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