8,442 research outputs found
Statefinder Revisited
The quality of supernova data will dramatically increase in the next few
years by new experiments that will add high-redshift supernova to the currently
known ones. In order to use this new data to discriminate between different
dark energy models, the statefinder diagnostic was suggested and investigated
by Alam et al. in the light of the proposed SuperNova Acceleration Probe (SNAP)
satellite. By making use of the same procedure presented by these authors, we
compare their analyzes with ours, which shows a more realistic supernovae
redshift distribution and do not assume that the intercept is known. We also
analyzed the behavior of the statefinder pair {r,s} and the alternative pair
{s,q} in the presence of offset errors
Correlation between Superconducting Transition Temperature and Increase of Nuclear Spin-Lattice Relaxation Rate Devided by Temperature at in the Hydrate Cobaltate NaCoOHO
We have performed Co-nuclear quadrupole resonance (NQR) studies on
NaCoOHO compounds with different Na () and hydrate
() contents. Two samples with different Na contents but nearly the same
values ( = 0.348, = 4.7 K ; = 0.339, = 4.6 K) were
investigated. The spin-lattice relaxation rate in the superconducting
(SC) and normal states is almost the same for the two samples except just above
. NQR measurements were also performed on different-hydrate-content
samples with different values, which were prepared from the same
Na-content ( = 0.348) sample. From measurements of using the
different-hydrate-content samples, it was found that a low- sample with
K has a larger residual density of states (DOS) in the SC state and
a smaller increase of just above than a high- sample with
= 4.7 K. The former behavior is consistent with that observed in
unconventional superconductors, and the latter suggests the relationship
between and the increase in DOS just above . This increase, which is
seemingly associated with the two-dimensionality of the CoO plane, is
considered to be one of the most important factors for the occurrence of
superconductivity.Comment: 5 pages, 5 figures, To be published in J. Phys. Soc. Jp
The first analytical expression to estimate photometric redshifts suggested by a machine
We report the first analytical expression purely constructed by a machine to
determine photometric redshifts () of galaxies. A simple and
reliable functional form is derived using galaxies from the Sloan
Digital Sky Survey Data Release 10 (SDSS-DR10) spectroscopic sample. The method
automatically dropped the and bands, relying only on , and
for the final solution. Applying this expression to other SDSS-DR10
galaxies, with measured spectroscopic redshifts (), we achieved a
mean and a scatter when averaged up to . The method was
also applied to the PHAT0 dataset, confirming the competitiveness of our
results when faced with other methods from the literature. This is the first
use of symbolic regression in cosmology, representing a leap forward in
astronomy-data-mining connection.Comment: 6 pages, 4 figures. Accepted for publication in MNRAS Letter
Mixing among light scalar mesons and L=1 q\bar{q} scalar mesons
Following the re-establishment of the \sigma(600) and the \kappa(900), the
light scalar mesons a_0(980) and f_0(980) together with the \sigma(600) and the
\kappa(900) are considered as the chiral scalar partner of pseudoscalar nonet
in SU(3) chiral symmetry, and the high mass scalar mesons a_0(1450),
K^*_0(1430), f_0(1370) and f_0(1710) turned out to be considered as the L=1
q\bar{q} scalar mesons. We assume that the high mass of the L=1 q\bar{q} scalar
mesons is caused by the mixing with the light scalar mesons. For the structure
of the light scalar mesons, we adopted the qq\bar{q}\bar{q} model in order to
explain the "scalar meson puzzle". The inter-mixing between the light scalar
nonet and the high mass L=1 q\bar{q} nonet and the intra-mixing among each
nonet are analyzed by including the glueball into the high mass scalar nonet.Comment: 16 pages, 5 figure
D2P2: database of disordered protein predictions
We present the Database of Disordered Protein Prediction (D2P2), available at http://d2p2.pro (including website source code). A battery of disorder predictors and their variants, VL-XT, VSL2b, PrDOS, PV2, Espritz and IUPred, were run on all protein sequences from 1765 complete proteomes (to be updated as more genomes are completed). Integrated with these results are all of the predicted (mostly structured) SCOP domains using the SUPERFAMILY predictor. These disorder/structure annotations together enable comparison of the disorder predictors with each other and examination of the overlap between disordered predictions and SCOP domains on a large scale. D2P2 will increase our understanding of the interplay between disorder and structure, the genomic distribution of disorder, and its evolutionary history. The parsed data are made available in a unified format for download as flat files or SQL tables either by genome, by predictor, or for the complete set. An interactive website provides a graphical view of each protein annotated with the SCOP domains and disordered regions from all predictors overlaid (or shown as a consensus). There are statistics and tools for browsing and comparing genomes and their disorder within the context of their position on the tree of life.
© The Author(s) 2012. Published by Oxford University Press
On the nature of light scalar mesons from their large behavior
We show how to obtain information about the states of an effective field
theory in terms of the underlying fundamental theory. In particular we analyze
the spectroscopic nature of meson resonances from the meson-meson scattering
amplitudes of the QCD low energy effective theory, combined with the expansion
in the large number of colors. The vectors follow a qqbar behavior, whereas the
sigma, kappa and f_0(980) scalars disappear for large N_c, in support of a
qqqbarqbar-like nature. The a_0 shows a similar pattern, but the uncertainties
are large enough to accommodate both interpretations.Comment: 4 pages. Slightly shortened version to appear in Phys. Rev. Lett. Two
typos correcte
Effects to Scalar Meson Decays of Strong Mixing between Low and High Mass Scalar Mesons
We analyze the mass spectroscopy of low and high mass scalar mesons and get
the result that the coupling strengths of the mixing between low and high mass
scalar mesons are very strong and the strengths of mixing for scalar
mesons and those of I=0 scalar mesons are almost same. Next, we analyze the
decay widths and decay ratios of these mesons and get the results that the
coupling constants for which represents the coupling of high
mass scalar meson -> two pseudoscalar mesons are almost same as the
coupling for the I=0. On the other hand, the coupling constant for
which represents the low mass scalar meson -> are far
from the coupling constant for I=0. We consider a resolution for this
discrepancy. Coupling constant for glueball -> is smaller than
the coupling . is .Comment: 15 pages, 6 figure
Cosmological Parameter Estimation from SN Ia data: a Model-Independent Approach
We perform a model independent reconstruction of the cosmic expansion rate
based on type Ia supernova data. Using the Union 2.1 data set, we show that the
Hubble parameter behaviour allowed by the data without making any hypothesis
about cosmological model or underlying gravity theory is consistent with a flat
LCDM universe having H_0 = 70.43 +- 0.33 and Omega_m=0.297 +- 0.020, weakly
dependent on the choice of initial scatter matrix. This is in closer agreement
with the recently released Planck results (H_0 = 67.3 +- 1.2, Omega_m = 0.314
+- 0.020) than other standard analyses based on type Ia supernova data. We
argue this might be an indication that, in order to tackle subtle deviations
from the standard cosmological model present in type Ia supernova data, it is
mandatory to go beyond parametrized approaches
Using gamma regression for photometric redshifts of survey galaxies
Machine learning techniques offer a plethora of opportunities in tackling big
data within the astronomical community. We present the set of Generalized
Linear Models as a fast alternative for determining photometric redshifts of
galaxies, a set of tools not commonly applied within astronomy, despite being
widely used in other professions. With this technique, we achieve catastrophic
outlier rates of the order of ~1%, that can be achieved in a matter of seconds
on large datasets of size ~1,000,000. To make these techniques easily
accessible to the astronomical community, we developed a set of libraries and
tools that are publicly available.Comment: Refereed Proceeding of "The Universe of Digital Sky Surveys"
conference held at the INAF - Observatory of Capodimonte, Naples, on
25th-28th November 2014, to be published in the Astrophysics and Space
Science Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodice,
6 pages, and 1 figur
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