1,897 research outputs found
Towards Rapid Parameter Estimation on Gravitational Waves from Compact Binaries using Interpolated Waveforms
Accurate parameter estimation of gravitational waves from coalescing compact
binary sources is a key requirement for gravitational-wave astronomy.
Evaluating the posterior probability density function of the binary's
parameters (component masses, sky location, distance, etc.) requires computing
millions of waveforms. The computational expense of parameter estimation is
dominated by waveform generation and scales linearly with the waveform
computational cost. Previous work showed that gravitational waveforms from
non-spinning compact binary sources are amenable to a truncated singular value
decomposition, which allows them to be reconstructed via interpolation at fixed
computational cost. However, the accuracy requirement for parameter estimation
is typically higher than for searches, so it is crucial to ascertain that
interpolation does not lead to significant errors. Here we provide a proof of
principle to show that interpolated waveforms can be used to recover posterior
probability density functions with negligible loss in accuracy with respect to
non-interpolated waveforms. This technique has the potential to significantly
increase the efficiency of parameter estimation.Comment: 7 pages, 2 figure
Self-Consistent Data Analysis of the Proton Structure Function g1 and Extraction of its Moments
The reanalysis of all available world data on the longitudinal asymmetry A||
is presented. The proton structure function g1 was extracted within a unique
framework of data inputs and assumptions. These data allowed for a reliable
evaluation of moments of the structure function g1 in the Q2 range from 0.2 up
to 30 GeV2. The Q2 evolution of the moments was studied in QCD by means of
Operator Product Expansion (OPE).Comment: Proceeding of 3rd International Symposium on the
Gerasimov-Drell-Hearn Sum Rule and its extensions, Old Dominion University,
Norfolk, Virginia June 2-5, 200
Nuclear corrections in neutrino-nucleus DIS and their compatibility with global NPDF analyses
We perform a global chi^2-analysis of nuclear parton distribution functions
using data from charged current neutrino-nucleus deep-inelastic scattering
(DIS), charged-lepton-nucleus DIS, and the Drell-Yan (DY) process. We show that
the nuclear corrections in nu-A DIS are not compatible with the predictions
derived from l^+A DIS and DY data. We quantify this result using a
hypothesis-testing criterion based on the chi^2 distribution which we apply to
the total chi^2 as well as to the chi^2 of the individual data sets. We find
that it is not possible to accommodate the data from nu-A and l^+A DIS by an
acceptable combined fit. Our result has strong implications for the extraction
of both nuclear and proton parton distribution functions using combined
neutrino and charged-lepton data sets.Comment: 5 page
Higher twist analysis of the proton g_1 structure function
We perform a global analysis of all available spin-dependent proton structure
function data, covering a large range of Q^2, 1 < Q^2 < 30 GeV^2, and calculate
the lowest moment of the g_1 structure function as a function of Q^2. From the
Q^2 dependence of the lowest moment we extract matrix elements of twist-4
operators, and determine the color electric and magnetic polarizabilities of
the proton to be \chi_E = 0.026 +- 0.015 (stat) + 0.021/-0.024 (sys) and \chi_B
= -0.013 -+ 0.007 (stat) - 0.010/+0.012 (sys), respectively.Comment: 6 pages, 2 figures, to appear in Phys. Lett.
Nuclear PDFs from neutrino deep inelastic scattering
We study nuclear effects in charged current deep inelastic neutrino-iron
scattering in the frame-work of a chi^2 analysis of parton distribution
functions. We extract a set of iron PDFs and show that under reasonable
assumptions it is possible to constrain the valence, light sea and strange
quark distributions. Our iron PDFs are used to compute x_{Bj}-dependent and
Q^2-dependent nuclear correction factors for iron structure functions which are
required in global analyses of free nucleon PDFs. We compare our results with
nuclear correction factors from neutrino-nucleus scattering models and
correction factors for charged lepton-iron scattering. We find that, except for
very high x_{Bj}, our correction factors differ in both shape and magnitude
from the correction factors of the models and charged-lepton scattering.Comment: 25 pages, 10 figures; minor updates to match published versio
nCTEQ15 - Global analysis of nuclear parton distributions with uncertainties in the CTEQ framework
We present the new nCTEQ15 set of nuclear parton distribution functions with
uncertainties. This fit extends the CTEQ proton PDFs to include the nuclear
dependence using data on nuclei all the way up to 208^Pb. The uncertainties are
determined using the Hessian method with an optimal rescaling of the
eigenvectors to accurately represent the uncertainties for the chosen tolerance
criteria. In addition to the Deep Inelastic Scattering (DIS) and Drell-Yan (DY)
processes, we also include inclusive pion production data from RHIC to help
constrain the nuclear gluon PDF. Furthermore, we investigate the correlation of
the data sets with specific nPDF flavor components, and asses the impact of
individual experiments. We also provide comparisons of the nCTEQ15 set with
recent fits from other groups.Comment: 35 page
Floristic Composition and Natural History Characteristics of Dry Forests in the Pacific
We compare the floristic composition of tropical dry forests at the stand level using Gentry's transect method (0.1 ha) in some of the largest and highest-quality remaining fragments in the Pacific (Hawai'i, 15 sites; Fiji, 9; the Marianas, 3; the Marquesas, 6; New Caledonia, 7) and compare results with neotropical dry forests. A total of 299 species or morphospecies =2.5 cm diameter at breast height were identified from all 40 sites in the Pacific. Rubiaceae (28 spp.), Euphorbiaceae (25 spp.), Fabaceae (23 spp.), Sapindaceae (18 spp.), and Myrtaceae (17 spp.) were the most speciose families in Pacific dry forest; however, no family dominated across regions in the Pacific. The most common species by frequency and density in each region were native with the exception of Hawai'i, which contains a high number of nonnative species. Observed and estimated (Chao 2) levels of native species richness show that New Caledonia and Fiji contain the highest species richness followed by Hawai'i, the Marianas, and the Marquesas. There is very little overlap at the native species level among regions, with Hawaiian dry forests the most dissimilar at the native species, genus, and family level and New Caledonia and Fiji the most similar. Unlike mainland neotropical dry forest, dry forests in the Pacific contain very few deciduous species and a low proportion of wind-dispersed species.There is a high proportion of dioecious species in Hawai'i, which is similar to the neotropics; however, other Pacific regions have fewer dioecious species
Global Analysis of Data on the Proton Structure Function g1 and Extraction of its Moments
Inspired by recent measurements with the CLAS detector at Jefferson Lab, we
perform a self-consistent analysis of world data on the proton structure
function g1 in the range 0.17 < Q2 < 30 (GeV/c)**2. We compute for the first
time low-order moments of g1 and study their evolution from small to large
values of Q2. The analysis includes the latest data on both the unpolarized
inclusive cross sections and the ratio R = sigmaL / sigmaT from Jefferson Lab,
as well as a new model for the transverse asymmetry A2 in the resonance region.
The contributions of both leading and higher twists are extracted, taking into
account effects from radiative corrections beyond the next-to-leading order by
means of soft-gluon resummation techniques. The leading twist is determined
with remarkably good accuracy and is compared with the predictions obtained
using various polarized parton distribution sets available in the literature.
The contribution of higher twists to the g1 moments is found to be
significantly larger than in the case of the unpolarized structure function F2.Comment: 18 pages, 13 figures, to appear in Phys. Rev.
Likelihood-ratio ranking of gravitational-wave candidates in a non-Gaussian background
We describe a general approach to detection of transient gravitational-wave
signals in the presence of non-Gaussian background noise. We prove that under
quite general conditions, the ratio of the likelihood of observed data to
contain a signal to the likelihood of it being a noise fluctuation provides
optimal ranking for the candidate events found in an experiment. The
likelihood-ratio ranking allows us to combine different kinds of data into a
single analysis. We apply the general framework to the problem of unifying the
results of independent experiments and the problem of accounting for
non-Gaussian artifacts in the searches for gravitational waves from compact
binary coalescence in LIGO data. We show analytically and confirm through
simulations that in both cases the likelihood ratio statistic results in an
improved analysis.Comment: 10 pages, 6 figure
Особенности моделирования прогнозных оценок экономических объектов
Теория и практика экономических исследований свидетельствует о том, что моделирование прогнозных оценок будущего состояния экономических объектов является наиболее успешным только в тех случаях, когда модель в полной мере отражает как природу процесса управления, так и специфику деловой среды, то есть речь идет, по сути, об адекватности используемой модели
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