170,073 research outputs found
Constraining H0 from Chandra Observations of Q0957+561
We report the detection of the lens cluster of the gravitational lens (GL)
system Q0957+561 from a deep observation with the Advanced CCD Imaging
Spectrometer on-board the Chandra X-ray Observatory. Intracluster X-ray
emission is found to be centered 4.3 +/- 1.3 arcsec east and 3.5(-0.6,+1.3)
arcsec north of image B, nearer than previous estimates. Its spectrum can be
modeled well with a thermal plasma model consistent with the emission
originating from a cluster at a redshift of 0.36. Our best-fit estimates of the
cluster temperature of T_e = 2.09(-0.54,+0.83) keV (90 percent confidence) and
mass distribution of the cluster are used to derive the convergence parameter
kappa, the ratio of the cluster surface mass density to the critical density
required for lensing. We estimate the convergence parameter at the location of
the lensed images A and B to be kappa_A = 0.22(+0.14,-0.07) and kappa_B =
0.21(+0.12,-0.07), respectively (90 percent confidence levels). The observed
cluster center, mass distribution and convergence parameter kappa provide
additional constraints to lens models of this system. Our new results break a
mass-sheet degeneracy in GL models of this system and provide better
constraints of ~ 29 percent (90 percent confidence levels) on the Hubble
constant. We also present results from the detection of the most distant X-ray
jet (z = 1.41) detected to date. The jet extends approximately 8 arcsec NE of
image A and three knots are resolved along the X-ray jet with flux densities
decreasing with distance from the core. The observed radio and optical flux
densities of the knots are fitted well with a synchrotron model and the X-ray
emission is modeled well with inverse Compton scattering of Cosmic Microwave
Background photons by synchrotron-emitting electrons in the jet.Comment: 18 pages, includes 7 figures, Accepted for publication in Ap
ELAS: A general-purpose computer program for the equilibrium problems of linear structures. Volume 2: Documentation of the program
A general purpose digital computer program for the in-core solution of linear equilibrium problems of structural mechanics is documented. The program requires minimum input for the description of the problem. The solution is obtained by means of the displacement method and the finite element technique. Almost any geometry and structure may be handled because of the availability of linear, triangular, quadrilateral, tetrahedral, hexahedral, conical, triangular torus, and quadrilateral torus elements. The assumption of piecewise linear deflection distribution insures monotonic convergence of the deflections from the stiffer side with decreasing mesh size. The stresses are provided by the best-fit strain tensors in the least squares at the mesh points where the deflections are given. The selection of local coordinate systems whenever necessary is automatic. The core memory is used by means of dynamic memory allocation, an optional mesh-point relabelling scheme and imposition of the boundary conditions during the assembly time
Poland in the Period of Economic Transition and Germany After Reunification an Attempt at Assessing Σ-Convergence
In 2009 and 2010 Poland and Germany are celebrating some important anniversaries - 20 years of the first free elections and the fall of the Berlin Wall. These jubilees inspire research aiming at taking stock of developments having unfolded over this time. Since the economic cohesion is high on the EU agenda, examining international and interregional differences seems an important research task. This article aims at evaluating and comparing σ-convergence (diminishing discrepancies of GDP p.c.) in Poland (1995-2005) and Germany (1992-2006) on three NUTS levels. Preliminary results point to inequalities regularly diminishing in Germany, however, growing in Poland. A tentative reasoning suggests that increasing values of regional differences observed in Poland might be a temporary phenomenon
How close are time series to power tail L\'evy diffusions?
This article presents a new and easily implementable method to quantify the
so-called coupling distance between the law of a time series and the law of a
differential equation driven by Markovian additive jump noise with heavy-tailed
jumps, such as -stable L\'evy flights. Coupling distances measure the
proximity of the empirical law of the tails of the jump increments and a given
power law distribution. In particular they yield an upper bound for the
distance of the respective laws on path space. We prove rates of convergence
comparable to the rates of the central limit theorem which are confirmed by
numerical simulations. Our method applied to a paleoclimate time series of
glacial climate variability confirms its heavy tail behavior. In addition this
approach gives evidence for heavy tails in data sets of precipitable water
vapor of the Western Tropical Pacific.Comment: 30 pages, 10 figure
Estimation of bivariate excess probabilities for elliptical models
Let be a random vector whose conditional excess probability
is of interest. Estimating this kind of
probability is a delicate problem as soon as tends to be large, since the
conditioning event becomes an extreme set. Assume that is elliptically
distributed, with a rapidly varying radial component. In this paper, three
statistical procedures are proposed to estimate for fixed ,
with large. They respectively make use of an approximation result of Abdous
et al. (cf. Canad. J. Statist. 33 (2005) 317--334, Theorem 1), a new second
order refinement of Abdous et al.'s Theorem 1, and a non-approximating method.
The estimation of the conditional quantile function
for large fixed is also addressed and these
methods are compared via simulations. An illustration in the financial context
is also given.Comment: Published in at http://dx.doi.org/10.3150/08-BEJ140 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
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