7,224 research outputs found
Vortex-state-mediated Josephson effect
The Josephson effect is a kind of macroscopic quantum phenomenon that
supercurrent flows through a Josephson junction without any voltage applied. We
predict a novel vortex-state-mediated Josephson effect in an SNS Josephson
junction supporting vortices. The vortex-state-mediated supercurrent is
enhanced or reduced significantly in magnitude depending on the junction
length, and exhibits several steps with the number of effective propagating
channels in current-phase evolution at zero temperature. At finite
temperatures, these supercurrent steps persist in the short junction limit, and
develop into sawtooth oscillations if the junction length becomes comparable to
the coherence length of the superconductor, and in later
case a supercurrent reversal can be observed. These findings may provide a
smoking-gun signature of vortex bound states in superconductors and promise
possible applications in future Josephson devices.Comment: 8 pages, 4 figure
Top-N Recommender System via Matrix Completion
Top-N recommender systems have been investigated widely both in industry and
academia. However, the recommendation quality is far from satisfactory. In this
paper, we propose a simple yet promising algorithm. We fill the user-item
matrix based on a low-rank assumption and simultaneously keep the original
information. To do that, a nonconvex rank relaxation rather than the nuclear
norm is adopted to provide a better rank approximation and an efficient
optimization strategy is designed. A comprehensive set of experiments on real
datasets demonstrates that our method pushes the accuracy of Top-N
recommendation to a new level.Comment: AAAI 201
Twin Learning for Similarity and Clustering: A Unified Kernel Approach
Many similarity-based clustering methods work in two separate steps including
similarity matrix computation and subsequent spectral clustering. However,
similarity measurement is challenging because it is usually impacted by many
factors, e.g., the choice of similarity metric, neighborhood size, scale of
data, noise and outliers. Thus the learned similarity matrix is often not
suitable, let alone optimal, for the subsequent clustering. In addition,
nonlinear similarity often exists in many real world data which, however, has
not been effectively considered by most existing methods. To tackle these two
challenges, we propose a model to simultaneously learn cluster indicator matrix
and similarity information in kernel spaces in a principled way. We show
theoretical relationships to kernel k-means, k-means, and spectral clustering
methods. Then, to address the practical issue of how to select the most
suitable kernel for a particular clustering task, we further extend our model
with a multiple kernel learning ability. With this joint model, we can
automatically accomplish three subtasks of finding the best cluster indicator
matrix, the most accurate similarity relations and the optimal combination of
multiple kernels. By leveraging the interactions between these three subtasks
in a joint framework, each subtask can be iteratively boosted by using the
results of the others towards an overall optimal solution. Extensive
experiments are performed to demonstrate the effectiveness of our method.Comment: Published in AAAI 201
Associated Production of Neutral Higgs Boson with Squark Pair in the Minimal Supersymmetric Standard Model with Explicit CP Violation at the CERN LHC
We investigate the associated production of neutral Higgs boson with squark
pair in the minimal supersymmetric standard model with and without explicit CP
violation, respectively. We show that the dominant productions in both cases
are always ones of the lightest neutral Higgs boson associated with the
lightest stop pair, which can reach a few pb, in the ranges of parameters
allowed by constraints from the electric dipole moment experiments. In most of
the parameter space, the total cross sections in the case with explicit CP
violation are significantly enhanced, compared with ones without explicit CP
violation. For some special parameters, several orders of magnitude enhancement
can be obtained.Comment: 4 pages, 7 figures, version to appear in PR
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