11,726 research outputs found
Apparent Clustering of Intermediate-redshift Galaxies as a Probe of Dark Energy
We show the apparent redshift-space clustering of galaxies in redshift range
of 0.2--0.4 provides surprisingly useful constraints on dark energy component
in the universe, because of the right balance between the density of objects
and the survey depth. We apply Fisher matrix analysis to the the Luminous Red
Galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS), as a concrete example.
Possible degeneracies in the evolution of the equation of state (EOS) and the
other cosmological parameters are clarified.Comment: 5 pages, 3 figures, Phys.Rev.Lett., replaced with the accepted
versio
Progress in thin film GaAs solar cells
Solar cells using polycrystalline films of gallium arsenid
Depth Estimation via Affinity Learned with Convolutional Spatial Propagation Network
Depth estimation from a single image is a fundamental problem in computer
vision. In this paper, we propose a simple yet effective convolutional spatial
propagation network (CSPN) to learn the affinity matrix for depth prediction.
Specifically, we adopt an efficient linear propagation model, where the
propagation is performed with a manner of recurrent convolutional operation,
and the affinity among neighboring pixels is learned through a deep
convolutional neural network (CNN). We apply the designed CSPN to two depth
estimation tasks given a single image: (1) To refine the depth output from
state-of-the-art (SOTA) existing methods; and (2) to convert sparse depth
samples to a dense depth map by embedding the depth samples within the
propagation procedure. The second task is inspired by the availability of
LIDARs that provides sparse but accurate depth measurements. We experimented
the proposed CSPN over two popular benchmarks for depth estimation, i.e. NYU v2
and KITTI, where we show that our proposed approach improves in not only
quality (e.g., 30% more reduction in depth error), but also speed (e.g., 2 to 5
times faster) than prior SOTA methods.Comment: 14 pages, 8 figures, ECCV 201
Study of Decays in the Family Non-universal Models
In a combined investigation of the decays,
constraints on the related couplings in family non-universal
models are derived. We find that within the allowed parameter space, the
recently observed forward-backward asymmetry in the
decay can be explained, by flipping the signs of the Wilson coefficients
and . With the obtained constraints, we also calculate
the branching ratio of the decay. The upper bound of our
prediction is near the upper bound given by CDF Collaboration recently.Comment: 19 pages, 4 figures, some errors corrected; Journal versio
Standard model plethystics
We study the vacuum geometry prescribed by the gauge invariant operators of the minimal supersymmetric standard model via the plethystic program. This is achieved by using several tricks to perform the highly computationally challenging Molien-Weyl integral, from which we extract the Hilbert series, encoding the invariants of the geometry at all degrees. The fully refined Hilbert series is presented as the explicit sum of 1422 rational functions. We found a good choice of weights to unrefine the Hilbert series into a rational function of a single variable, from which we can read off the dimension and the degree of the vacuum moduli space of the minimal supersymmetric standard model gauge invariants. All data in Mathematica format are also presented
The Evolution of Optical Depth in the Ly-alpha Forest: Evidence Against Reionization at z~6
We examine the evolution of the IGM Ly-alpha optical depth distribution using
the transmitted flux probability distribution function (PDF) in a sample of 63
QSOs spanning absorption redshifts 1.7 < z < 5.8. The data are compared to two
theoretical optical depth distributions: a model distribution based on the
density distribution of Miralda-Escude et al. (2000) (MHR00), and a lognormal
distribution. We assume a uniform UV background and an isothermal IGM for the
MHR00 model, as has been done in previous works. Under these assumptions, the
MHR00 model produces poor fits to the observed flux PDFs at redshifts where the
optical depth distribution is well sampled, unless large continuum corrections
are applied. However, the lognormal optical depth distribution fits the data at
all redshifts with only minor continuum adjustments. We use a simple
parametrization for the evolution of the lognormal parameters to calculate the
expected mean transmitted flux at z > 5.4. The lognormal optical depth
distribution predicts the observed Ly-alpha and Ly-beta effective optical
depths at z > 5.7 while simultaneously fitting the mean transmitted flux down
to z = 1.6. If the evolution of the lognormal distribution at z < 5 reflects a
slowly-evolving density field, temperature, and UV background, then no sudden
change in the IGM at z ~ 6 due to late reionization appears necessary. We have
used the lognormal optical depth distribution without any assumption about the
underlying density field. If the MHR00 density distribution is correct, then a
non-uniform UV background and/or IGM temperature may be required to produce the
correct flux PDF. We find that an inverse temperature-density relation greatly
improves the PDF fits, but with a large scatter in the equation of state index.
[Abridged]Comment: 45 pages, 16 figures, submitted to Ap
Soliton with a Pion Field in the Global Color Symmetry Model
We calculate the property of the global color symmetry model soliton with the
pion field being included explicitly. The calculated results indicate that the
pion field provides a strong attraction so that the eigen-energy of a quark and
the mass of a soliton reduce drastically, in contrast to those with only the
sigma field.Comment: 15 pages, 2 figure
Antiferromagnetic and Orbital Ordering on a Diamond Lattice Near Quantum Criticality
We present neutron scattering measurements on powder samples of the spinel
FeSc2S4 that reveal a previously unobserved magnetic ordering transition
occurring at 11.8(2)~K. Magnetic ordering occurs subsequent to a subtle
cubic-to-tetragonal structural transition which distorts Fe coordinating sulfur
tetrahedra lifting the orbital degeneracy. The application of 1~GPa hydrostatic
pressure appears to destabilize this N\'eel state, reducing the transition
temperature to 8.6(8)~K and redistributing magnetic spectral weight to higher
energies. The relative magnitudes of ordered
and fluctuating moments show that the
magnetically ordered ground state of FeSc2S4 is drastically renormalized and in
proximity to criticality.Comment: 16 pages, 12 figure
The Variability of Sagittarius A* at Centimeter Wavelengths
We present the results of a 3.3-year project to monitor the flux density of
Sagittarius A* at 2.0, 1.3, and 0.7 cm with the VLA. The fully calibrated light
curves for Sgr A* at all three wavelengths are presented. Typical errors in the
flux density are 6.1%, 6.2%, and 9.2% at 2.0, 1.3, and 0.7 cm, respectively.
There is preliminary evidence for a bimodal distribution of flux densities,
which may indicate the existence of two distinct states of accretion onto the
supermassive black hole. At 1.3 and 0.7 cm, there is a tail in the distribution
towards high flux densities. Significant variability is detected at all three
wavelengths, with the largest amplitude variations occurring at 0.7 cm. The rms
deviation of the flux density of Sgr A* is 0.13, 0.16, and 0.21 Jy at 2.0, 1.3,
and 0.7 cm, respectively. During much of this monitoring campaign, Sgr A*
appeared to be relatively quiescent compared to results from previous
campaigns. At no point during the monitoring campaign did the flux density of
Sgr A* more than double its mean value. The mean spectral index of Sgr A* is
alpha=0.20+/-0.01, with a standard deviation of 0.14. The spectral index
appears to depend linearly on the observed flux density at 0.7 cm with a
steeper index observed during outbursts. This correlation is consistent with
the expectation for outbursts that are self-absorbed at wavelengths of 0.7 cm
or longer and inconsistent with the effects of simple models for interstellar
scintillation. Much of the variability of Sgr A*, including possible time lags
between flux density changes at the different wavelengths, appears to occur on
time scales less than the time resolution of our observations (8 days). Future
observations should focus on the evolution of the flux density on these time
scales.Comment: 16 pages, 10 figures, accepted for publication in A
Estimating Depth from RGB and Sparse Sensing
We present a deep model that can accurately produce dense depth maps given an
RGB image with known depth at a very sparse set of pixels. The model works
simultaneously for both indoor/outdoor scenes and produces state-of-the-art
dense depth maps at nearly real-time speeds on both the NYUv2 and KITTI
datasets. We surpass the state-of-the-art for monocular depth estimation even
with depth values for only 1 out of every ~10000 image pixels, and we
outperform other sparse-to-dense depth methods at all sparsity levels. With
depth values for 1/256 of the image pixels, we achieve a mean absolute error of
less than 1% of actual depth on indoor scenes, comparable to the performance of
consumer-grade depth sensor hardware. Our experiments demonstrate that it would
indeed be possible to efficiently transform sparse depth measurements obtained
using e.g. lower-power depth sensors or SLAM systems into high-quality dense
depth maps.Comment: European Conference on Computer Vision (ECCV) 2018. Updated to
camera-ready version with additional experiment
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