11,859 research outputs found
Quantized Quasi-Two Dimensional Bose-Einstein Condensates with Spatially Modulated Nonlinearity
We investigate the localized nonlinear matter waves of the quasi-two
dimensional Bose-Einstein condensates with spatially modulated nonlinearity in
harmonic potential. It is shown that the whole Bose-Einstein condensates,
similar to the linear harmonic oscillator, can have an arbitrary number of
localized nonlinear matter waves with discrete energies, which are
mathematically exact orthogonal solutions of the Gross-Pitaevskii equation.
Their novel properties are determined by the principle quantum number n and
secondary quantum number l: the parity of the matter wave functions and the
corresponding energy levels depend only on n, and the numbers of density
packets for each quantum state depend on both n and l which describe the
topological properties of the atom packets. We also give an experimental
protocol to observe these novel phenomena in future experiments.Comment: 5 pages, 5 figure
Is the partner of in the nonet?
Based on a mass matrix, the mixing angle of the axial vector
states and is determined to be , and the
theoretical results about the decay and production of the two states are
presented. The theoretical results are in good agreement with the present
experimental results, which suggests that can be assigned as the
partner of in the nonet. We also suggest that
the existence of needs further experimental confirmation.Comment: Latex, 6 pages, to be published in Chin. Phys. let
A Novel Truncated Norm Regularization Method for Multi-channel Color Image Denoising
Due to the high flexibility and remarkable performance, low-rank
approximation methods has been widely studied for color image denoising.
However, those methods mostly ignore either the cross-channel difference or the
spatial variation of noise, which limits their capacity in real world color
image denoising. To overcome those drawbacks, this paper is proposed to denoise
color images with a double-weighted truncated nuclear norm minus truncated
Frobenius norm minimization (DtNFM) method. Through exploiting the nonlocal
self-similarity of the noisy image, the similar structures are gathered and a
series of similar patch matrices are constructed. For each group, the DtNFM
model is conducted for estimating its denoised version. The denoised image
would be obtained by concatenating all the denoised patch matrices. The
proposed DtNFM model has two merits. First, it models and utilizes both the
cross-channel difference and the spatial variation of noise. This provides
sufficient flexibility for handling the complex distribution of noise in real
world images. Second, the proposed DtNFM model provides a close approximation
to the underlying clean matrix since it can treat different rank components
flexibly. To solve the problem resulted from DtNFM model, an accurate and
effective algorithm is proposed by exploiting the framework of the alternating
direction method of multipliers (ADMM). The generated subproblems are discussed
in detail. And their global optima can be easily obtained in closed-form.
Rigorous mathematical derivation proves that the solution sequences generated
by the algorithm converge to a single critical point. Extensive experiments on
synthetic and real noise datasets demonstrate that the proposed method
outperforms many state-of-the-art color image denoising methods
Vortex images on Ba{1-x}KxFe2As2 observed directly by the magnetic force microscopy
The vortex states on optimally doped Ba0.6K0.4Fe2As2 and underdoped
Ba0.77K0.23Fe2As2 single crystals are imaged by magnetic force microscopy at
various magnetic fields below 100 Oe. Local triangular vortex clusters are
observed in optimally doped samples. The vortices are more ordered than those
in Ba(Fe{1-x}Co{x})2As2, and the calculated pinning force per unit length is
about 1 order of magnitude weaker than that in optimally Co-doped 122 at the
same magnetic field, indicating that the Co doping at the Fe sites induces
stronger pinning. The proportion of six-neighbored vortices to the total amount
increases quickly with increasing magnetic field, and the estimated value
reaches 100% at several tesla. Vortex chains are also found in some local
regions, which enhance the pinning force as well as the critical current
density. Lines of vortex chains are observed in underdoped samples, and they
may have originated from the strong pinning near the twin boundaries arising
from the structural transition.Comment: 7 pages, 8 figure
Multi-channel Nuclear Norm Minus Frobenius Norm Minimization for Color Image Denoising
Color image denoising is frequently encountered in various image processing
and computer vision tasks. One traditional strategy is to convert the RGB image
to a less correlated color space and denoise each channel of the new space
separately. However, such a strategy can not fully exploit the correlated
information between channels and is inadequate to obtain satisfactory results.
To address this issue, this paper proposes a new multi-channel optimization
model for color image denoising under the nuclear norm minus Frobenius norm
minimization framework. Specifically, based on the block-matching, the color
image is decomposed into overlapping RGB patches. For each patch, we stack its
similar neighbors to form the corresponding patch matrix. The proposed model is
performed on the patch matrix to recover its noise-free version. During the
recovery process, a) a weight matrix is introduced to fully utilize the noise
difference between channels; b) the singular values are shrunk adaptively
without additionally assigning weights. With them, the proposed model can
achieve promising results while keeping simplicity. To solve the proposed
model, an accurate and effective algorithm is built based on the alternating
direction method of multipliers framework. The solution of each updating step
can be analytically expressed in closed-from. Rigorous theoretical analysis
proves the solution sequences generated by the proposed algorithm converge to
their respective stationary points. Experimental results on both synthetic and
real noise datasets demonstrate the proposed model outperforms state-of-the-art
models
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