11,758 research outputs found
Eigenstates of Paraparticle Creation Operators
Eigenstates of the parabose and parafermi creation operators are constructed.
In the Dirac contour representation, the parabose eigenstates correspond to the
dual vectors of the parabose coherent states. In order , conserved-charge
parabose creation operator eigenstates are also constructed. The contour forms
of the associated resolutions of unity are obtained.Comment: 14 pages, LaTex file, no macros, no figure
The Pairwise Peculiar Velocity Dispersion of Galaxies: Effects of the Infall
We study the reliability of the reconstruction method which uses a modelling
of the redshift distortions of the two-point correlation function to estimate
the pairwise peculiar velocity dispersion of galaxies. In particular, the
dependence of this quantity on different models for the infall velocity is
examined for the Las Campanas Redshift Survey. We make extensive use of
numerical simulations and of mock catalogs derived from them to discuss the
effect of a self-similar infall model, of zero infall, and of the real infall
taken from the simulation. The implications for two recent discrepant
determinations of the pairwise velocity dispersion for this survey are
discussed.Comment: minor changes in the discussion; accepted for publication in ApJ; 8
pages with 2 figures include
Exploiting the Composite Step Strategy to the BiconjugateA-Orthogonal Residual Method for Non-Hermitian Linear Systems
The Biconjugate A-Orthogonal Residual (BiCOR) method carried out in finite precision arithmetic by means of the biconjugate A-orthonormalization procedure may possibly tend to suffer from two sources of numerical instability, known as two kinds of breakdowns, similarly to those of the Biconjugate Gradient (BCG) method. This paper naturally exploits the composite step strategy employed in the development of the composite step BCG (CSBCG) method into the BiCOR method to cure one of the breakdowns called as pivot breakdown. Analogously to the CSBCG method, the resulting interesting variant, with only a minor modification to the usual implementation of the BiCOR method, is able to avoid near pivot breakdowns and compute all the well-defined BiCOR iterates stably on the assumption that the underlying biconjugate A-orthonormalization procedure does not break down. Another benefit acquired is that it seems to be a viable algorithm providing some further practically desired smoothing of the convergence history of the norm of the residuals, which is justified by numerical experiments. In addition, the exhibited method inherits the promising advantages of the empirically observed stability and fast convergence rate of the BiCOR method over the BCG method so that it outperforms the CSBCG method to some extent
Sparse Feature Extraction for Activity Detection Using Low-Resolution IR Streams
In this paper, we propose an ultra-low-resolution infrared (IR) images based activity recognition method which is suitable for monitoring in elderly care-house and modern smart home. The focus is on the analysis of sequences of IR frames, including single subject doing daily activities. The pixels are considered as independent variables because of the lacking of spatial dependencies between pixels in the ultra-low resolution image. Therefore, our analysis is based on the temporal variation of the pixels in vectorised sequences of several IR frames, which results in a high dimensional feature space and an "n<; <; p" problem. Two different sparse analysis strategies are used and compared: Sparse Discriminant Analysis (SDA) and Sparse Principal Component Analysis (SPCA). The extracted sparse features are tested with four widely used classifiers: Support Vector Machines (SVM), Random Forests (RF), K-Nearest Neighbours (KNN) and Logistic Regression (LR). To prove the availability of the sparse features, we also compare the classification results of the noisy data based sparse features and non-sparse based features respectively. The comparison shows the superiority of sparse methods in terms of noise tolerance and accuracy
Scaling properties of the redshift power spectrum: theoretical models
We report the results of an analysis of the redshift power spectrum
in three typical Cold Dark Matter (CDM) cosmological models, where
is the cosine of the angle between the wave vector and the line-of-sight.
Two distinct biased tracers derived from the primordial density peaks of
Bardeen et al. and the cluster-underweight model of Jing, Mo, & B\"orner are
considered in addition to the pure dark matter models. Based on a large set of
high resolution simulations, we have measured the redshift power spectrum for
the three tracers from the linear to the nonlinear regime. We investigate the
validity of the relation - guessed from linear theory - in the nonlinear regime
where
is the real space power spectrum, and equals . The
damping function which should generally depend on , , and
, is found to be a function of only one variable
. This scaling behavior extends into the nonlinear regime,
while can be accurately expressed as a Lorentz function - well known from
linear theory - for values . The difference between
and the pairwise velocity dispersion defined by the 3-D peculiar velocity of
the simulations (taking ) is about 15%. Therefore is a
good indicator of the pairwise velocity dispersion. The exact functional form
of depends on the cosmological model and on the bias scheme. We have given
an accurate fitting formula for the functional form of for the models
studied.Comment: accepted for publication in ApJ;24 pages with 7 figures include
Transverse localization and slow propagation of light
The effect of finite control beam on the transverse spatial profile of the
slow light propagation in an electromagnetically induced transparency medium is
studied. We arrive at a general criterion in terms of eigenequation, and
demonstrate the existence of a set of localized, stationary transverse modes
for the negative detuning of the probe signal field. Each of these
diffraction-free transverse modes has its own characteristic group velocity,
smaller than the conventional theoretical result without considering the
transverse spatial effect
The finite size effect of galaxies on the cosmic virial theorem and the pairwise peculiar velocity dispersions
We discuss the effect of the finite size of galaxies on estimating
small-scale relative pairwise peculiar velocity dispersions from the cosmic
virial theorem (CVT). Specifically we evaluate the effect by incorporating the
finite core radius in the two-point correlation function of mass, i.e.
and the effective gravitational force
softening on small scales. We analytically obtain the lowest-order
correction term for which is in quantitative agreement with the
full numerical evaluation. With a nonzero and/or the cosmic virial
theorem is no longer limited to the case of . We present accurate
fitting formulae for the CVT predicted pairwise velocity dispersion for the
case of . Compared with the idealistic point-mass approximation
(), the finite size effect can significantly reduce the small-scale
velocity dispersions of galaxies at scales much larger than and .
Even without considering the finite size of galaxies, nonzero values for
are generally expected, for instance, for cold dark matter (CDM) models with a
scale-invariant primordial spectrum. For these CDM models, a reasonable force
softening r_s\le 100 \hikpc would have rather tiny effect. We present the CVT
predictions for the small-scale pairwise velocity dispersion in the CDM models
normalized by the COBE observation. The implication of our results for
confrontation of observations of galaxy pair-wise velocity dispersions and
theoretical predictions of the CVT is also discussed.Comment: 18 pages. LaTeX text and 8 postcript figures. submitted to Ap
Associated Production of a Top Quark and a Charged Higgs Boson
We compute the inclusive and differential cross sections for the associated
production of a top quark along with a charged Higgs boson at hadron colliders
to next-to-leading order (NLO) in perturbative quantum chromodynamics (QCD) and
in supersymmetric QCD. For small Higgs boson masses we include top quark pair
production diagrams with subsequent top quark decay into a bottom quark and a
charged Higgs boson. We compare the NLO differential cross sections obtained in
the bottom parton picture with those for the gluon-initiated production process
and find good agreement. The effects of supersymmetric loop contributions are
explored. Only the corrections to the Yukawa coupling are sizable in the
potential discovery region at the CERN Large Hadron Collider (LHC). All
expressions and numerical results are fully differential, permitting selections
on the momenta of both the top quark and the charged Higgs boson.Comment: 15 pages, 9 figures; section, figures, equations and references
added, version to appear in PRD, 33 pages, 11 figure
Structural Diversity of Class 1 integrons and their associated gene cassettes in Klebsiella pneumoniae isolates from a hospital in China
published_or_final_versio
Accelerating exhaustive pairwise metagenomic comparisons
In this manuscript, we present an optimized and parallel version of our previous work IMSAME, an exhaustive gapped aligner for the pairwise and accurate comparison of metagenomes. Parallelization strategies are applied to take advantage of modern multiprocessor architectures. In addition, sequential optimizations in CPU time and memory consumption are provided. These algorithmic and computational enhancements enable IMSAME to calculate near optimal alignments which are used to directly assess similarity between metagenomes without requiring reference databases. We show that the overall efficiency of the parallel implementation is superior to 80% while retaining scalability as the number of parallel cores used increases. Moreover, we also show thats equential optimizations yield up to 8x speedup for scenarios with larger data.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec
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