18,521 research outputs found
Pion-Nucleon Sigma Term in Lattice QCD
We calculate both connected and disconnected contribution to the -
-term in quenched lattice QCD with Wilson quark action on a lattice at . The latter is evaluated with the aid of the variant
wall source method, which was previously applied successfully for extraction of
- scattering lengths and meson mass. We found that the
disconnected contribution is about twice larger than the connected one. The
value for the full - term MeV is consistent
with the experimental estimates. The nucleon matrix element of the strange
quark density is fairly large in our result.Comment: 11 pages. Latex file. Figures are also included as ps file
Fluorine abundances in planetary nebulae
We have determined fluorine abundances from the F II 4789 and F IV 4060
nebular emission lines for a sample of planetary nebulae (PNe). Our results
show that fluorine is generally overabundant in PNe, thus providing new
evidence for the synthesis of fluorine in asymptotic giant branch (AGB) stars.
[F/O] is found to be positively correlated with the C/O abundance ratio, in
agreement with the predictions of theoretical models of fluorine production in
thermally pulsing AGB stars. A large enhancement of fluorine is observed in the
Wolf-Rayet PN NGC 40, suggesting that high mass-loss rates probably favor the
survival of fluorine.Comment: 4 pages, 3 figures, accepted for publication in ApJ Letter
CP-PACS Result for the Quenched Light Hadron Spectrum
The quenched hadron spectrum in the continuum obtained with the Wilson quark
action in recent simulations on the CP-PACS is presented. Results for the light
quark masses and the QCD scale parameter are reported.Comment: Talk presented by K. Kanaya at Lattice97, Edinburg
Comment on Decay
We calculate the rate for decay using Chiral
Perturbation Theory. This isospin violating process results from -
mixing, and its amplitude is proportional to . Experimental information on the branching
ratio for can provide insight into the pattern of
violation in radiative decays.Comment: 7 pages with 2 figures not included but available upon request,
CALT-68-191
Lattice QCD Calculation of Hadron Scattering Lengths
Method of calculating hadron multi-point functions and disconnected quark
loop contributions which are not readily accessible through conventional
techniques is proposed. Results are reported for pion-pion, pion-nucleon and
nucleon-nucleon scattering lengths and the flavor singlet-non singlet meson
mass splitting estimated in quenched QCD.Comment: 6 pages. Contribution to Lattice '93. Latex file, style file
espcrc2.sty needed.(appended at the end) Figures are also included as epsf
file
Orbital selectivity causing anisotropy and particle-hole asymmetry in the charge density wave gap of -TaS
We report an in-depth Angle Resolved Photoemission Spectroscopy (ARPES) study
on -TaS, a canonical incommensurate Charge Density Wave (CDW) system.
This study demonstrates that just as in related incommensurate CDW systems,
-TaSe and -NbSe, the energy gap () of
-TaS is localized along the K-centered Fermi surface barrels and is
particle-hole asymmetric. The persistence of even at
temperatures higher than the CDW transition temperature
in -TaS, reflects the similar pseudogap (PG) behavior observed
previously in -TaSe and -NbSe. However, in sharp contrast to
-NbSe, where is non-zero only in the vicinity
of a few "hot spots" on the inner K-centered Fermi surface barrels,
in -TaS is non-zero along the entirety of both
K-centered Fermi surface barrels. Based on a tight-binding model, we attribute
this dichotomy in the momentum dependence and the Fermi surface specificity of
between otherwise similar CDW compounds to the
different orbital orientations of their electronic states that are involved in
CDW pairing. Our results suggest that the orbital selectivity plays a critical
role in the description of incommensurate CDW materials.Comment: 6 pages, 4 figure
CP-PACS results for quenched QCD spectrum with the Wilson action
We present progress report of a CP-PACS calculation of quenched QCD spectrum
with the Wilson quark action. Light hadron masses and meson decay constants are
obtained at 5.9, 6.1, and 6.25 on lattices with a physical extent of 3
fm, and for the range of quark mass corresponding to 0.4. Nucleon mass at each appears to be a convex function of
quark mass, and consequently the value at the physical quark mass is much
smaller than previously thought. Hadron masses extrapolated to the continuum
limit exhibits a significant deviation from experimental values: with meson
mass to fix strange quark mass, strange meson and baryon masses are
systematically lower. Light quark masses determined from the axial Ward
identity are shown to agree with those from perturbation theory in the
continuum limit. Decay constants of mesons are also discussed.Comment: 12 pages, Latex(espcrc2,epsf), 17 ps figures. Talk presented by
T.Yoshi\'e at the International Workshop on ``LATTICE QCD ON PARALLEL
COMPUTERS'', 10-15 March 1997, Center for Computational Physics, University
of Tsukub
Quenched Light Hadron Spectrum with the Wilson Quark Action: Final Results from CP-PACS
We report the final results of the CP-PACS calculation for the quenched light
hadron spectrum with the Wilson quark action. Our data support the presence of
quenched chiral singularities, and this motivates us to use mass formulae based
on quenched chiral perturbation theory in order to extrapolate hadron masses to
the physical point. Hadron masses and decay constants in the continuum limit
show unambiguous systematic deviations from experiment. We also report the
results for light quark masses.Comment: LATTICE98(spectrum). The poster at Lattice98 can be obtained from
http://www.rccp.tsukuba.ac.jp/people/yoshie/Lat98.Poster
Joint Learning of Intrinsic Images and Semantic Segmentation
Semantic segmentation of outdoor scenes is problematic when there are
variations in imaging conditions. It is known that albedo (reflectance) is
invariant to all kinds of illumination effects. Thus, using reflectance images
for semantic segmentation task can be favorable. Additionally, not only
segmentation may benefit from reflectance, but also segmentation may be useful
for reflectance computation. Therefore, in this paper, the tasks of semantic
segmentation and intrinsic image decomposition are considered as a combined
process by exploring their mutual relationship in a joint fashion. To that end,
we propose a supervised end-to-end CNN architecture to jointly learn intrinsic
image decomposition and semantic segmentation. We analyze the gains of
addressing those two problems jointly. Moreover, new cascade CNN architectures
for intrinsic-for-segmentation and segmentation-for-intrinsic are proposed as
single tasks. Furthermore, a dataset of 35K synthetic images of natural
environments is created with corresponding albedo and shading (intrinsics), as
well as semantic labels (segmentation) assigned to each object/scene. The
experiments show that joint learning of intrinsic image decomposition and
semantic segmentation is beneficial for both tasks for natural scenes. Dataset
and models are available at: https://ivi.fnwi.uva.nl/cv/intrinsegComment: ECCV 201
Observational Constraints on Cosmological Models with the Updated Long Gamma-Ray Bursts
In the present work, by the help of the newly released Union2 compilation
which consists of 557 Type Ia supernovae (SNIa), we calibrate 109 long
Gamma-Ray Bursts (GRBs) with the well-known Amati relation, using the
cosmology-independent calibration method proposed by Liang {\it et al.}. We
have obtained 59 calibrated high-redshift GRBs which can be used to constrain
cosmological models without the circularity problem (we call them ``Hymnium''
GRBs sample for convenience). Then, we consider the joint constraints on 7
cosmological models from the latest observational data, namely, the combination
of 557 Union2 SNIa dataset, 59 calibrated Hymnium GRBs dataset (obtained in
this work), the shift parameter from the WMAP 7-year data, and the distance
parameter of the measurement of the baryon acoustic oscillation (BAO) peak
in the distribution of SDSS luminous red galaxies. We also briefly consider the
comparison of these 7 cosmological models.Comment: 19 pages, 3 tables, 10 figures, revtex4; v2: accepted for publication
in JCAP; v3: published versio
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