3,171 research outputs found
Oracle Based Active Set Algorithm for Scalable Elastic Net Subspace Clustering
State-of-the-art subspace clustering methods are based on expressing each
data point as a linear combination of other data points while regularizing the
matrix of coefficients with , or nuclear norms.
regularization is guaranteed to give a subspace-preserving affinity (i.e.,
there are no connections between points from different subspaces) under broad
theoretical conditions, but the clusters may not be connected. and
nuclear norm regularization often improve connectivity, but give a
subspace-preserving affinity only for independent subspaces. Mixed ,
and nuclear norm regularizations offer a balance between the
subspace-preserving and connectedness properties, but this comes at the cost of
increased computational complexity. This paper studies the geometry of the
elastic net regularizer (a mixture of the and norms) and uses
it to derive a provably correct and scalable active set method for finding the
optimal coefficients. Our geometric analysis also provides a theoretical
justification and a geometric interpretation for the balance between the
connectedness (due to regularization) and subspace-preserving (due to
regularization) properties for elastic net subspace clustering. Our
experiments show that the proposed active set method not only achieves
state-of-the-art clustering performance, but also efficiently handles
large-scale datasets.Comment: 15 pages, 6 figures, accepted to CVPR 2016 for oral presentatio
Active-IRS Aided Wireless Network: System Modeling and Performance Analysis
Active intelligent reflecting surface (IRS) enables flexible signal
reflection control with \emph{power amplification}, thus effectively
compensating the product-distance path-loss in conventional passive-IRS aided
systems. In this letter, we characterize the communication performance of an
active-IRS aided single-cell wireless network. To this end, we first propose a
\emph{customized} IRS deployment strategy, where the active IRSs are uniformly
deployed within a ring concentric with the cell to serve the users far from the
base station. Next, given the Nakagami- fading channel, we characterize the
cascaded active-IRS channel by using the \emph{mixture Gamma distribution}
approximation and derive a closed-form expression for the mean signal-to-noise
ratio (SNR) at the user averaged over channel fading. Moreover, we numerically
show that to maximize the system performance, it is necessary to choose a
proper active-IRS density given a fixed number of total reflecting elements,
which significantly differs from the passive-IRS case for which the centralized
IRS deployment scheme is better. Furthermore, the active-IRS aided wireless
network achieves higher spatial throughput than the passive-IRS counterpart
when the total number of reflecting elements is small
Unconventional Superconducting Symmetry in a Checkerboard Antiferromagnet
We use a renormalized mean field theory to study the Gutzwiller projected BCS
states of the extended Hubbard model in the large limit, or the
--- model on a two-dimensional checkerboard lattice. At small
, the frustration due to the diagonal terms of and does not
alter the -wave pairing symmetry, and the negative (positive)
enhances (suppresses) the pairing order parameter. At large , the
ground state has an extended s-wave symmetry. At the intermediate , the
ground state is or -wave with time reversal symmetry broken.Comment: 6 pages, 6 figure
Charge Ordered RVB States in the Doped Cuprates
We study charge ordered d-wave resonating valence bond states (dRVB) in the
doped cuprates, and estimate the energies of these states in a generalized model by using a renormalized mean field theory. The long range Coulomb
potential tends to modulate the charge density in favor of the charge ordered
RVB state. The possible relevance to the recently observed
checkerboard patterns in tunnelling conductance in high cuprates is
discussed.Comment: 4 pages, 4 figures, 3 table
Strongly enhanced light-matter interaction in a hybrid photonic-plasmonic resonator
We propose a hybrid photonic-plasmonic resonant structure which consists of a
metal nanoparticle (MNP) and a whispering gallery mode (WGM) microcavity. It is
found that the hybrid mode enables a strong interaction between the light and
matter, and the single-atom cooperativity is enhanced by more than two orders
of magnitude compared to that in a bare WGM microcavity. This remarkable
improvement originates from two aspects: (1) the MNP offers a highly enhanced
local field in the vicinity of an emitter, and (2), surprisingly, the
high-\textit{Q} property of WGMs can be maintained in the presence of the MNP.
Thus the present system has great advantages over a single microcavity or a
single MNP, and holds great potential in quantum optics, nonlinear optics and
highly sensitive biosening.Comment: 5 pages, 4 figure
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