42,116 research outputs found
A fully discrete evolving surface finite element method
In this paper we consider a time discrete evolving surface finite element method for the advection and diffusion of a conserved scalar quantity on a moving surface. In earlier papers using a suitable variational formulation in time dependent Sobolev space we proposed and analyzed a finite element method using surface finite elements on evolving triangulated surfaces [IMA J. Numer Anal., 25 (2007), pp. 385--407; Math. Comp., to appear]. Optimal order L2(Î(t)) and H1(Î(t)) error bounds were proved for linear finite elements. In this work we prove optimal order error bounds for a backward Euler time discretization
Polarizabilities of Si^{2+}: a benchmark test of theory and experiment
We have calculated electric-dipole polarizabilities of the 3s^2 ^1S_0, 3s3p
^3P_0, and 3s3p ^1P_1 states of the Si^{2+} ion using recently developed
configuration interaction + all-order method. Detailed evaluation of the
uncertainties of the final results is carried out. Our value for the ground
state electric-dipole polarizability 11.670(13) a.u. is in excellent agreement
with the resonant excitation Stark ionization spectroscopy value 11.669(9) a.u.
[Komara et al., J. Phys. B 38, 87 (2005); Mitroy, Phys. Rev. A 78, 052515
(2008)]. This work represents the most precise benchmark test to date of theory
and experiment in divalent atoms. The near cancellation of the ns^2 ^1S_0
ground state and the lowest nsnp ^3P_0 polarizabilities previously observed in
B+, Al+, In+, Tl+, and Pb^{2+} is also found in Si^{2+} ion.Comment: 6 page
Immigrant Earnings Differences Across Admission Categories and Landing Cohorts in Canada
This study uses longitudinal IMDB micro data to document the annual earnings outcomes of Canadian immigrants in four major admission categories (skill-assessed independent economic principal applicants, accompanying economic immigrants, family class immigrants, and refugees) and three annual landing cohorts (those for the years 1982, 1988, and 1994) over the first ten years following their landing in Canada as permanent residents. The findings provide a ten-year earnings signature for the four broad immigrant admission categories in Canada. The studyâs first major finding is that skill-assessed economic immigrants had consistently and substantially the highest annual earnings levels among the four admission categories for both male and female immigrants in all three landing cohorts. Family class immigrants or refugees generally had the lowest earnings levels. An important related finding is that refugees exhibited substantially the highest earnings growth rates for both male and female immigrants in all three landing cohorts, while independent economic or family class immigrants generally had the lowest earnings growth rates over their first post-landing decade in Canada. The studyâs second major finding is that economic recessions appear to have had clearly discernible negative effects on immigrantsâ earnings levels and growth rates; moreover, these adverse effects were much more pronounced for male immigrants than for female immigrants.Immigrant earnings, admission categories, Canadian immigrants
Cosmic Rays from Gamma Ray Bursts in the Galaxy
The rate of terrestrial irradiation events by galactic gamma-ray bursts
(GRBs) is estimated using recent standard-energy results. We assume that GRBs
accelerate high-energy cosmic rays, and present results of three-dimensional
simulations of cosmic rays moving in the Galactic magnetic field and diffusing
through pitch-angle scattering. An on-axis GRB extinction event begins with a
powerful prompt gamma-ray and neutron pulse, followed by a longer-lived phase
from cosmic-ray protons and neutron-decay protons that diffuse towards Earth.
Our results force a reinterpretation of reported ~ 10^{18} eV cosmic-ray
anisotropies and offer a rigorous test of the model where high-energy cosmic
rays originate from GRBs, which will soon be tested with the Auger Observatory.Comment: 9 pages, 4 figures, ApJ Letters, in press. Clarified limit of
test-particle approximation, prediction that Auger will not confirm SUGAR
source. (Data may not appear onscreen at low magnification.) Simulations at
http://heseweb.nrl.navy.mil/gamma/~dermer/invest/sim/index.ht
B-> rho pi, rho rho, pi pi: hunting for alpha
We determine the domains of the values of unitarity triangle angle alpha,
allowed by the charmless strangeless B_d (\bar B_d) decays.Comment: 16 pages. Recent Belle results on CP asymmetries in
B_d(\bar{B}_d)-->rho^+ rho^- decays are taken into account. Version to be
published in Yad.Fi
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