7,459 research outputs found
Information-Theoretical Learning of Discriminative Clusters for Unsupervised Domain Adaptation
We study the problem of unsupervised domain adaptation, which aims to adapt
classifiers trained on a labeled source domain to an unlabeled target domain.
Many existing approaches first learn domain-invariant features and then
construct classifiers with them. We propose a novel approach that jointly learn
the both. Specifically, while the method identifies a feature space where data
in the source and the target domains are similarly distributed, it also learns
the feature space discriminatively, optimizing an information-theoretic metric
as an proxy to the expected misclassification error on the target domain. We
show how this optimization can be effectively carried out with simple
gradient-based methods and how hyperparameters can be cross-validated without
demanding any labeled data from the target domain. Empirical studies on
benchmark tasks of object recognition and sentiment analysis validated our
modeling assumptions and demonstrated significant improvement of our method
over competing ones in classification accuracies.Comment: Appears in Proceedings of the 29th International Conference on
Machine Learning (ICML 2012
Correlated spontaneous symmetry breaking induced by zero-point fluctuations in a quantum mixture
We propose a form of spontaneous symmetry breaking driven by zero-point
quantum fluctuations. To be specific, we consider the low-energy dynamics of a
mixture of two species of spin- Bose gases. It is demonstrated that the
quantum fluctuations lift a degeneracy regarding the relative orientations of
the spin directors of the two species, and result in correlation or locking
between these macroscopic variables. This locking persists in the presence of
the trapping potential and weak magnetic fields, allowing, in principle, an
experimental probe of this correlated spontaneous symmetry breaking, as a
macroscopic manifestation of zero-point quantum fluctuations.Comment: 6 page
Off-diagonal Long-Range Order and Supersolidity in a Quantum Solid with Vacancies
We consider a lattice of bosonic atoms, whose number N may be smaller than
the number of lattice sites M. We study the Hartree-Fock wave function built up
from localized wave functios w(\mathbf{r}) of single atoms, with nearest
neighboring overlap. The zero-momentum particle number is expressed in terms of
permanents of matrices. In one dimension, it is analytically calculated to be
\alpha*N(M-N+1)/M, with \alpha=|\int w(\mathbf{r})d\Omega|^2/[(1+2a)l], where a
is the nearest-neighboring overlap, l is the lattice constant. \alpha is of the
order of 1. The result indicates that the condensate fraction is proportional
to and of the same order of magnitude as that of the vacancy concentration,
hence there is off-diagonal long-range order or Bose-Einstein condensation of
atoms when the number of vacancies M-N is a finite fraction of the number of
the lattice sites M.Comment: 12 pages. A few references are added. To appear in PR
CHY formula and MHV amplitudes
In this paper, we study the relation between the Cachazo-He-Yuan (CHY)
formula and the maximal-helicity-violating (MHV) amplitudes of Yang-Mills and
gravity in four dimensions. We prove that only one special rational solution of
the scattering equations found by Weinzierl support the MHV amplitudes. Namely,
localized at this solution, the integrated CHY formula reproduces the
Parke-Taylor formula for Yang-Mills amplitudes as well as the Hodges formula
for gravitational amplitudes. This is achieved by developing techniques, in a
manifestly M\"obius covariant formalism, to explicitly compute relevant reduced
Pfaffians/determinants. We observe and prove two interesting properties (or
identities), which facilitate the computations. We also check that all the
other solutions to the scattering equations do not support the MHV
amplitudes, and prove analytically that this is indeed true for the other
special rational solution proposed by Weinzierl, that actually supports the
anti-MHV amplitudes.Comment: 28 pages, 4 figures, published versio
A resnet-based universal method for speckle reduction in optical coherence tomography images
In this work we propose a ResNet-based universal method for speckle reduction
in optical coherence tomography (OCT) images. The proposed model contains 3
main modules: Convolution-BN-ReLU, Branch and Residual module. Unlike
traditional algorithms, the model can learn from training data instead of
selecting parameters manually such as noise level. Application of this proposed
method to the OCT images shows a more than 22 dB signal-to-noise ratio
improvement in speckle noise reduction with minimal structure blurring. The
proposed method provides strong generalization ability and can process noisy
other types of OCT images without retraining. It outperforms other filtering
methods in suppressing speckle noises and revealing subtle features
Efficient Simulation Budget Allocation for Subset Selection Using Regression Metamodels
This research considers the ranking and selection (R&S) problem of selecting
the optimal subset from a finite set of alternative designs. Given the total
simulation budget constraint, we aim to maximize the probability of correctly
selecting the top-m designs. In order to improve the selection efficiency, we
incorporate the information from across the domain into regression metamodels.
In this research, we assume that the mean performance of each design is
approximately quadratic. To achieve a better fit of this model, we divide the
solution space into adjacent partitions such that the quadratic assumption can
be satisfied within each partition. Using the large deviation theory, we
propose an approximately optimal simulation budget allocation rule in the
presence of partitioned domains. Numerical experiments demonstrate that our
approach can enhance the simulation efficiency significantly
Metaflow: A DAG-Based Network Abstraction for Distributed Applications
In the past decade, increasingly network scheduling techniques have been
proposed to boost the distributed application performance. Flow-level metrics,
such as flow completion time (FCT), are based on the abstraction of flows yet
they cannot capture the semantics of communication in a cluster application.
Being aware of this problem, coflow is proposed as a new network abstraction.
However, it is insufficient to reveal the dependencies between computation and
communication. As a result, the real application performance can be hurt,
especially in the absence of hard barriers. Based on the computation DAG of the
application, we propose an expressive abstraction namely metaflow that resides
in the middle of the two extreme points of flows and coflows. Evaluation
results show that metaflow-based scheduling can outperform the coflow-based
algorithm by 1.78x
Transport evidence for the coexistence of the topological surface state and a two-dimensional electron gas in BiSbTe3 topological insulator
Topological insulators (TIs) are new insulating materials with exotic surface
states, where the motion of charge carriers is described by the Dirac equations
and their spins are locked in a perpendicular direction to their momentum.
Recent studies by angle-resolved photoemission spectroscopy have demonstrated
that a conventional two-dimensional electron gas can coexist with the
topological surface state due to the quantum confinement effect. The
coexistence is expected to give rise to exotic transport properties, which,
however, have not been explored so far. Here, we report a magneto-transport
study on single crystals of the topological insulator BiSbTe3. Besides
Shubnikov-de Haas oscillations and weak anti-localization (WAL) from the
topological surface state, we also observed a crossover from the weak
anti-localization to weak localization (WL) with increasing magnetic field,
which is temperature dependent and exhibits two-dimensional features. The
crossover is proposed to be the transport manifestation of the coexistence of
the topological surface state and two-dimensional electron gas on the surface
of TIs.Comment: 11 pages, 4 figure
Crossover from a continuum study of chiral susceptibility
We derive a model-independent integral formula for chiral susceptibility and
attempt to present a continuum model study of it within the framework of
Dyson-Schwinger Equations. An appropriate regularization is implemented to
remove the temperature-independent quadratic divergence inherent in this
quantity. While it demonstrates a second-order phase transition characteristic
in the chiral limit, the result obtained supports a crossover at physical
current quark masses, which is in good agreement with recent lattice studies.Comment: 15 pages, 2 figures, revtex
Experimental test of Heisenberg's measurement uncertainty relation based on statistical distances
Incompatible observables can be approximated by compatible observables in
joint measurement or measured sequentially, with constrained accuracy as
implied by Heisenberg's original formulation of the uncertainty principle.
Recently, Busch, Lahti, and Werner proposed inaccuracy trade-off relations
based on statistical distances between probability distributions of measurement
outcomes [Phys. Rev. Lett. 111, 160405 (2013); Phys. Rev. A 89, 012129 (2014)].
Here we reform their theoretical framework, derive an improved relation for
qubit measurement, and perform an experimental test on a spin system. The
relation reveals that the worst-case inaccuracy is tightly bounded from below
by the incompatibility of target observables, and is verified by the experiment
employing joint measurement in which two compatible but typically
non-commutative observables on one qubit are measured simultaneously
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