10,765 research outputs found
Information Filtering on Coupled Social Networks
In this paper, based on the coupled social networks (CSN), we propose a
hybrid algorithm to nonlinearly integrate both social and behavior information
of online users. Filtering algorithm based on the coupled social networks,
which considers the effects of both social influence and personalized
preference. Experimental results on two real datasets, \emph{Epinions} and
\emph{Friendfeed}, show that hybrid pattern can not only provide more accurate
recommendations, but also can enlarge the recommendation coverage while
adopting global metric. Further empirical analyses demonstrate that the mutual
reinforcement and rich-club phenomenon can also be found in coupled social
networks where the identical individuals occupy the core position of the online
system. This work may shed some light on the in-depth understanding structure
and function of coupled social networks
Quantum Phase Transition in the Sub-Ohmic Spin-Boson Model: Extended Coherent-state Approach
We propose a general extended coherent state approach to the qubit (or
fermion) and multi-mode boson coupling systems. The application to the
spin-boson model with the discretization of a bosonic bath with arbitrary
continuous spectral density is described in detail, and very accurate solutions
can be obtained. The quantum phase transition in the nontrivial sub-Ohmic case
can be located by the fidelity and the order-parameter critical exponents for
the bath exponents can be correctly given by the fidelity
susceptibility, demonstrating the strength of the approach.Comment: 4 pages, 3 figure
Quantum phase transitions in coupled two-level atoms in a single-mode cavity
The dipole-coupled two-level atoms(qubits) in a single-mode resonant cavity
is studied by extended bosonic coherent states. The numerically exact solution
is presented. For finite systems, the first-order quantum phase transitions
occur at the strong interatomic interaction. Similar to the original Dicke
model, this system exhibits a second-order quantum phase transition from the
normal to the superradiant phases. Finite-size scaling for several observables,
such as the average fidelity susceptibility, the order parameter, and
concurrence are performed for different interatomic interactions. The obtained
scaling exponents suggest that interatomic interactions do not change the
universality class.Comment: 13 pages, 5 figure
Discovery-and-Selection: Towards Optimal Multiple Instance Learning for Weakly Supervised Object Detection
Weakly supervised object detection (WSOD) is a challenging task that requires
simultaneously learn object classifiers and estimate object locations under the
supervision of image category labels. A major line of WSOD methods roots in
multiple instance learning which regards images as bags of instances and
selects positive instances from each bag to learn the detector. However, a
grand challenge emerges when the detector inclines to converge to
discriminative parts of objects rather than the whole objects. In this paper,
under the hypothesis that optimal solutions are included in local minima, we
propose a discovery-and-selection approach fused with multiple instance
learning (DS-MIL), which finds rich local minima and select optimal solution
from multiple local minima. To implement DS-MIL, an attention module is
proposed so that more context information can be captured by feature maps and
more valuable proposals can be collected during training. With proposal
candidates, a selection module is proposed to select informative instances for
object detector. Experimental results on commonly used benchmarks show that our
proposed DS-MIL approach can consistently improve the baselines, reporting
state-of-the-art performance
Regiodivergent enantioselective C-H functionalization of Boc-1,3-oxazinanes for the synthesis of beta(2)- and beta(3)-amino acids
beta(2)- and beta(3)-amino acids are important chiral building blocks for the design of new pharmaceuticals and peptidomimetics. Here, we report a straightforward regio- and enantiodivergent access to these compounds using a one-pot reaction composed of sparteine-mediated enantioselective lithiation of a Boc-1,3-oxazinane, transmetallation to zinc and direct or migratory Negishi coupling with an organic electrophile. The regioselectivity of the Negishi coupling was highly ligand-controlled and switch-able to obtain the C4- or the C5-functionalized product exclusively. High enantioselectivities were achieved on a broad range of examples, and a catalytic version in chiral diamine was developed using the (+)-sparteine surrogate. Selected C4- and C5-functionalized Boc-1,3-oxazinanes were subsequently converted to highly enantioenriched beta(2)- and beta(3)-amino acids with the (R) or (S) configuration, depending on the sparteine enantiomer employed in the lithiation step
Accurate numerical solution to the finite-size Dicke model
By using extended bosonic coherent states, a new technique to solve the Dicke
model exactly is proposed in the numerical sense. The accessible system size is
two orders of magnitude higher than that reported in literature. Finite-size
scaling for several observables, such as the ground-state energy, Berry phase,
and concurrence are analyzed. The existing discrepancy for the scaling exponent
of the concurrence is reconciled.Comment: 4 pages, 5 figures. Phys. Rev. A (in press, a Rapid Communication
Stable interaction-induced Anderson-like localization embedded in standing waves
We uncover the interaction-induced \emph{stable self-localization} of bosons
in disorder-free superlattices. In these nonthermalized multi-particle states,
one of the particles forms a superposition of multiple standing waves, so that
it provides a quasirandom potential to localize the other particles. We derive
effective Hamiltonians for self-localized states and find their energy level
spacings obeying the Poisson statistics for Anderson-like localization.
Surprisingly, we find that the correlated self-localization can be solely
induced by interaction in the well-studied nonintegrable Bose-Hubbard models,
which has been overlooked for a long time. We propose a dynamical scheme to
detect self-localization, where long-time quantum walks of a single particle
form a superposition of multiple standing waves for trapping the subsequently
loaded particles. Our work provides an experimentally feasible way to realize
stable Anderson-like localization in translation-invariant disorder-free
systems
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