65 research outputs found
Many-body approach to proton emission and the role of spectroscopic factors
The process of proton emission from nuclei is studied by utilizing the
two-potential approach of Gurvitz and Kalbermann in the context of the full
many-body problem. A time-dependent approach is used for calculating the decay
width. Starting from an initial many-body quasi-stationary state, we employ the
Feshbach projection operator approach and reduce the formalism to an effective
one-body problem. We show that the decay width can be expressed in terms of a
one-body matrix element multiplied by a normalization factor. We demonstrate
that the traditional interpretation of this normalization as the square root of
a spectroscopic factor is only valid for one particular choice of projection
operator. This causes no problem for the calculation of the decay width in a
consistent microscopic approach, but it leads to ambiguities in the
interpretation of experimental results. In particular, spectroscopic factors
extracted from a comparison of the measured decay width with a calculated
single-particle width may be affected.Comment: 17 pages, Revte
On correctness in RDF stream processor benchmarking
Two complementary benchmarks have been proposed so far for the evaluation and continuous improvement of RDF stream processors: SRBench and LSBench. They put a special focus on different features of the evaluated systems, including coverage of the streaming extensions of SPARQL supported by each processor, query processing throughput, and an early analysis of query evaluation correctness, based on comparing the results obtained by different processors for a set of queries. However, none of them has analysed the operational semantics of these processors in order to assess the correctness of query evaluation results. In this paper, we propose a characterization of the operational semantics of RDF stream processors, adapting well-known models used in the stream processing engine community: CQL and SECRET. Through this formalization, we address correctness in RDF stream processor benchmarks, allowing to determine the multiple answers that systems should provide. Finally, we present CSRBench, an extension of SRBench to address query result correctness verification using an automatic method
SRBench: A streaming RDF/SPARQL benchmark
We introduce SRBench, a general-purpose benchmark primarily designed for streaming RDF/SPARQL engines, completely based on real-world data sets from the Linked Open Data cloud. With the increasing problem of too much streaming data but not enough tools to gain knowledge from them, researchers have set out for solutions in which Semantic Web technologies are adapted and extended for publishing, sharing, analysing and understanding streaming data. To help researchers and users comparing streaming RDF/SPARQL (strRS) engines in a standardised application scenario, we have designed SRBench, with which one can assess the abilities of a strRS engine to cope with a broad range of use cases typically encountered in real-world scenarios. The data sets used in the benchmark have been carefully chosen, such that they represent a realistic and relevant usage of streaming data. The benchmark defines a concise, yet omprehensive set of queries that cover the major aspects of strRS processing. Finally, our work is complemented with a functional evaluation on three representative strRS engines: SPARQLStream, C-SPARQL and CQELS. The presented results are meant to give a first baseline and illustrate the state-of-the-art
Phenomenological Tests of Supersymmetric A_4 Family Symmetry Model of Neutrino Mass
Recently Babu, Ma and Valle proposed a model of quark and lepton mixing based
on symmetry. Within this model the lepton and slepton mixings are
intimately related. We perform a numerical study in order to derive the slepton
masses and mixings in agreement with present data from neutrino physics. We
show that, starting from three-fold degeneracy of the neutrino masses at a high
energy scale, a viable low energy neutrino mass matrix can indeed be obtained
in agreement with constraints on lepton flavour violating
and decays. The resulting slepton spectrum must necessarily
include at least one mass below 200 GeV which can be produced at the LHC. The
predictions for the absolute Majorana neutrino mass scale eV
ensure that the model will be tested by future cosmological tests and
searches.
Rates for lepton flavour violating processes
in the range of sensitivity of current
experiments are typical in the model, with BR(\mu \to e \gamma) \gsim
10^{-15} and the lower bound BR. To first
approximation, the model leads to maximal leptonic CP violation in neutrino
oscillations.Comment: 23 pages, 7 figure
Charged lepton Flavor Violation in Supersymmetry with Bilinear R-Parity Violation
The simplest unified extension of the Minimal Supersymmetric Standard Model
with bi-linear R-parity violation naturally predicts a hierarchical neutrino
mass spectrum, suitable to explain atmospheric and solar neutrino fluxes. We
study whether the individual violation of the lepton numbers L_{e,mu,tau} in
the charged sector can lead to measurable rates for BR(mu->e gamma)and
$BR(tau-> mu gamma). We find that some of the R-parity violating terms that are
compatible with the observed atmospheric neutrino oscillations could lead to
rates for mu->e gamma measurable in projected experiments. However, the Delta
m^2_{12} obtained for those parameters is too high to be compatible with the
solar neutrino data, excluding therefore the possibility of having measurable
rates for mu->e gamma in the model.Comment: 29 pages, 8 figures. Constraint from solar neutrino data included,
conclusions changed respect v
Supersymmetric Relations Among Electromagnetic Dipole Operators
Supersymmetric contributions to all leptonic electromagnetic dipole operators
have essentially identical diagramatic structure. With approximate slepton
universality this allows the muon anomalous magnetic moment to be related to
the electron electric dipole moment in terms of supersymmetric phases, and to
radiative flavor changing lepton decays in terms of small violations of slepton
universality. If the current discrepancy between the measured and Standard
Model values of the muon anomalous magnetic moment is due to supersymmetry, the
current bound on the electron electric dipole moment then implies that the
phase of the electric dipole operator is less than . Likewise
the current bound on decay implies that the fractional
selectron-smuon mixing in the left-left mass squared matrix, \delta m_{\smuon
\selectron}^2 / m_{\slepton}^2, is less than . These relations and
constraints are fairly insensitive to details of the superpartner spectrum for
moderate to large .Comment: Latex, 38 pages, 2 figure
Larger and faster: revised properties and a shorter orbital period for the WASP-57 planetary system from a pro-am collaboration
Transits in the WASP-57 planetary system have been found to occur half an hour earlier than expected. We present 10 transit light curves from amateur telescopes, on which this discovery was based, 13 transit light curves from professional facilities which confirm and refine this finding, and high-resolution imaging which show no evidence for nearby companions. We use these data to determine a new and precise orbital ephemeris, and measure the physical properties of the system. Our revised orbital period is 4.5 s shorter than found from the discovery data alone, which explains the early occurrence of the transits. We also find both the star and planet to be larger and less massive than previously thought. The measured mass and radius of the planet are now consistent with theoretical models of gas giants containing no heavy-element core, as expected for the subsolar metallicity of the host star. Two transits were observed simultaneously in four passbands. We use the resulting light curves to measure the planet’s radius as a function of wavelength, finding that our data are sufficient in principle but not in practise to constrain its atmospheric properties. We conclude with a discussion of the current and future status of transmission photometry studies for probing the atmospheres of gas-giant transiting planets
Desempenho de equipamentos utilizados para o fechamento de taipas abertas para drenagem no arroz irrigado
Tratamento de sementes de trigo com zinco: armazenabilidade, componentes do rendimento e teor do elemento nas sementes
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