46,380 research outputs found
One-dimensional relativistic dissipative system with constant force and its quantization
For a relativistic particle under a constant force and a linear velocity
dissipation force, a constant of motion is found. Problems are shown for
getting the Hamiltoninan of this system. Thus, the quantization of this system
is carried out through the constant of motion and using the quantization of the
velocity variable. The dissipative relativistic quantum bouncer is outlined
within this quantization approach.Comment: 11 pages, no figure
Sieve-based confidence intervals and bands for L\'{e}vy densities
The estimation of the L\'{e}vy density, the infinite-dimensional parameter
controlling the jump dynamics of a L\'{e}vy process, is considered here under a
discrete-sampling scheme. In this setting, the jumps are latent variables, the
statistical properties of which can be assessed when the frequency and time
horizon of observations increase to infinity at suitable rates. Nonparametric
estimators for the L\'{e}vy density based on Grenander's method of sieves was
proposed in Figueroa-L\'{o}pez [IMS Lecture Notes 57 (2009) 117--146]. In this
paper, central limit theorems for these sieve estimators, both pointwise and
uniform on an interval away from the origin, are obtained, leading to pointwise
confidence intervals and bands for the L\'{e}vy density. In the pointwise case,
our estimators converge to the L\'{e}vy density at a rate that is arbitrarily
close to the rate of the minimax risk of estimation on smooth L\'{e}vy
densities. In the case of uniform bands and discrete regular sampling, our
results are consistent with the case of density estimation, achieving a rate of
order arbitrarily close to , where is the
number of observations. The convergence rates are valid, provided that is
smooth enough and that the time horizon and the dimension of the sieve
are appropriately chosen in terms of .Comment: Published in at http://dx.doi.org/10.3150/10-BEJ286 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Beyond the soft photon approximation in radiative production and decay of charged vector mesons
We study the effects of model-dependent contributions and the electric
quadrupole moment of vector mesons in the decays and
. Their interference with the amplitude originating
from the radiation due to electric charges vanishes for photons emitted
collinearly to the charged particle in the final state. This brings further
support to our claim in previous works, that measurements of the photon energy
spectrum for nearly collinear photons in those decays are suitable for a first
measurement of the magnetic dipole moment of charged vector mesons.Comment: 13 pages, 2 eps figures, Latex. Accepted for publication in Journal
of Physics G: Nuclear and Particle Physics(2001
La investigación sobre los efectos de las single sex vs. coeducational schools
El trabajo aborda las cuestiones metodológicas de investigación
acerca de la influencia del agrupamiento escolar según
el sexo (escuelas separadas vs. mixtas) sobre diversas variables
educativas de los alumnos. Se recurre a los diseños
antes-y-después y a los estudios nacionales de largo alcance.
Estos plantean un problema de validez interna, pues son
estudios ex post facto. ¿Cómo controlar las variables extrañas
asociadas al alumno, familia y escuela? Dichos estudios
lo permiten dado que son masivos en muestra y en variables.
Se defiende la posición de que solamente se han de
controlar las variables no asociadas al modelo de escuelas
mixta y separada. La validez externa se considera de menor
importancia
A boxy bulge in the Milky Way. Inversion of the stellar statistics equation with 2MASS data
Inverting the stellar statistics equation from 2MASS star counts, we obtain
the 3D density distribution of the Galactic bulge as well as its luminosity
function in the K-band. This results in a boxy bulge with axial ratios
1:0.5:0.4 and a major axis angle with respect to the Sun-galactic center of
.Comment: 5 pages, accepted to be published in A&
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