1,693 research outputs found
Ionization of molecular hydrogen and deuterium by a frequency-doubled Ti:sapphire laser pulses
A theoretical study of the intense-field single ionization of molecular
hydrogen or deuterium oriented either parallel or perpendicular to a linear
polarized laser pulse (400 nm) is performed for different internuclear
separations and pulse lengths in an intensity range of W
cm. The investigation is based on a non-perturbative treatment that
solves the full time-dependent Schr\"odinger equation of both correlated
electrons within the fixed-nuclei and the dipole approximation. The results for
various internuclear separations are used to obtain the ionization yields of
molecular hydrogen and deuterium in their ground vibrational states. An atomic
model is used to identify the influence of the intrinsic diatomic two-center
character of the problem.Comment: 13 pages, 9 figure
Sidereal time analysis as a toll for the study of the space distribution of sources of gravitational waves
Gravitational wave (GW) detectors operating on a long time range can be used
for the study of space distribution of sources of GW bursts or to put strong
upper limits on the GW signal of a wide class of source candidates. For this
purpose we propose here a sidereal time analysis to analyze the output signal
of GW detectors. Using the characteristics of some existing detectors, we
demonstrate the capability of the sidereal time analysis to give a clear
signature of different localizations of GW sources: the Galactic Center, the
Galactic Plane, the Supergalactic plane, the Great Attractor. On the contrary,
a homogeneous 3D-distribution of GW sources gives a signal without features. In
this paper we consider tensor gravitational waves with randomly oriented
polarization. We consider GW detectors at fixed positions on the Earth, and a
fixed orientation of the antenna.Comment: 7 pages, 6 figure
Flavor asymmetry of polarized antiquark distributions and semi-inclusive DIS
The -expansion of QCD suggests large flavor asymmetries of the
polarized antiquark distributions in the nucleon. This is confirmed by model
calculations in the large- limit (chiral quark-soliton model), which give
sizable results for and . We compute the contributions of
these flavor asymmetries to the spin asymmetries in hadron production in
semi-inclusive deep-inelastic scattering. We show that the large flavor
asymmetries predicted by the chiral quark-soliton model are consistent with the
recent HERMES data for spin asymmetries in charged hadron production.Comment: 21 pages, LaTeX2e, 9 eps figures include
Sudbury project (University of Muenster-Ontario Geological Survey): Field studies 1984-1989 - summary of results
In cooperation between the Ontario Geological Survey and the Institute of Geology and Institute of Planetology, geological, petrological, and geochemical studies were carried out on impact-related phenomena of the Sudbury structure during the last decade. The main results of the field studies are briefly reviewed. Footwall rocks, sublayer, and lower sections of the Sudbury Igneous Complex (SIC) were mainly mapped and sampled in the northern (Levack Township) and western (Trillabelle and Sultana Properties) parts of the north range. Within these mapping areas Sudbury Breccias (SB) and Footwall Breccias (FB) were studied; SB were also investigated along extended profiles beyond the north and south ranges up to 55 km from the SIC. The Onaping Formation (OF) and the upper section of the SIC were studied both in the north range (Morgan and Dowling Townships) and in the southern east range (Capreol and McLennan Townships)
Galaxy Harassment and the Evolution of Clusters of Galaxies
Disturbed spiral galaxies with high rates of star formation pervaded clusters
of galaxies just a few billion years ago, but nearby clusters exclude spirals
in favor of ellipticals. ``Galaxy harassment" (frequent high speed galaxy
encounters) drives the morphological transformation of galaxies in clusters,
provides fuel for quasars in subluminous hosts and leaves detectable debris
arcs. Simulated images of harassed galaxies are strikingly similar to the
distorted spirals in clusters at observed by the Hubble Space
Telescope.Comment: Submitted to Nature. Latex file, 7 pages, 10 photographs in gif and
jpeg format included. 10 compressed postscript figures and text available
using anonymous ftp from ftp://ftp-hpcc.astro.washington.edu/pub/hpcc/moore/
(mget *) Also available at http://www-hpcc.astro.washington.edu/papers
Quantitative measure of evolution of bright cluster galaxies at moderate redshifts
Using archival data from the Hubble Space Telescope, we study the
quantitative morphological evolution of spectroscopically confirmed bright
galaxies in the core regions of nine clusters ranging in redshift from to . We use morphological parameters derived from two
dimensional bulge-disk decomposition to study the evolution. We find an
increase in the mean bulge-to-total luminosity ratio as the Universe
evolves. We also find a corresponding increase in the fraction of early type
galaxies and in the mean S\'ersic index. We discuss these results and their
implications to physical mechanisms for evolution of galaxy morphology.Comment: 5 pages, 3 figures, Accepted for publication in MNRAS: Letter
Analytical approximations of K-corrections in optical and near-infrared bands
To compare photometric properties of galaxies at different redshifts, the
fluxes need to be corrected for the changes of effective rest-frame wavelengths
of filter bandpasses, called K-corrections. Usual approaches to compute them
are based on the template fitting of observed spectral energy distributions
(SED) and, thus, require multi-colour photometry. Here, we demonstrate that, in
cases of widely used optical and near-infrared filters, K-corrections can be
precisely approximated as two-dimensional low-order polynomials of only two
parameters: redshift and one observed colour. With this minimalist approach, we
present the polynomial fitting functions for K-corrections in SDSS ugriz, UKIRT
WFCAM YJHK, Johnson-Cousins UBVR_cI_c, and 2MASS JHK_s bands for galaxies at
redshifts Z<0.5 based on empirically-computed values obtained by fitting
combined optical-NIR SEDs of a set of 10^5 galaxies constructed from SDSS DR7
and UKIDSS DR5 photometry using the Virtual Observatory. For luminous red
galaxies we provide K-corrections as functions of their redshifts only. In two
filters, g and r, we validate our solutions by computing K-corrections directly
from SDSS DR7 spectra. We also present a K-corrections calculator, a web-based
service for computing K-corrections on-line.Comment: 13 pages, 7 figures, 25 tables. Accepted for publication in MNRAS.
This version contains low-resolution figures. The "K-corrections calculator"
service is available at http://kcor.sai.msu.ru
- âŠ