10,584 research outputs found
Angular separations of the lensed QSO images
We have analyzed the observed image separations of the gravitationally lensed
images of QSOs for a possible correlation with the source redshift. Contrary to
the previously noted anti-correlation based on a smaller data set, no
correlation is found for the currently available data. We have calculated the
average image separations of the lensed QSOs as a function of source redshifts,
for isothermal spheres with cores in a flat universe, taking into account the
amplification bias caused by lensing. The shape of the distribution of average
image separation as a function of redshift is very robust and is insensitive to
most model parameters. Observations are found to be roughly consistent with the
theoretical results for models which assume the lens distribution to be (i)
Schechter luminosity function which, however, can not produce images with large
separation and (ii) the mass condensations in a cold dark matter universe, as
given by the Press-Schechter theory if an upper limit of 1-7
M is assumed on the mass of the condensations.Comment: 20 pages, 7 postscript figures, accepted for publication in The
Astrophysical Journa
Coherent dynamics of photoinduced nucleation processes
We study the dynamics of initial nucleation processes of photoinduced
structural change of molecular crystals. In order to describe the nonadiabatic
transition in each molecule, we employ a model of localized electrons coupled
with a fully quantized phonon mode, and the time-dependent Schr\"odinger
equation for the model is numerically solved. We found a minimal model to
describe the nucleation induced by injection of an excited state of a single
molecule in which multiple types of intermolecular interactions are required.
In this model coherently driven molecular distortion plays an important role in
the successive conversion of electronic states which leads to photoinduced
cooperative phenomena.Comment: 14 pages, 5 figure
Orientation isotope effect in ion–molecule reactions
This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/67/10/10.1063/1.434632.A simple kinematicmodel is proposed to account for the kinetic isotope effect (KIE) upon the reactions of simple ions X+ with HD. This model is based upon (1) the fact that the displacement of the center of polarizability from the center of mass in the HD molecule will affect the alignment of the reactants, (2) the fact that, for many ions X+, reaction must occur by a surface crossing mechanism, and (3) the assumption that the ratio XH+/(XH++XD+) equals the fraction of intimate collisions in which the H end of HD is oriented towards the ion at the moment the reactants pass over the centrifugal barrier in the effective radial potential (or cross over to the X–HD+ surface if the crossing occurs before the centrifugal barrier is reached). Use of the ion–induced dipole potential for the reactants permits the derivation of an analytic expression for the KIE. With no adjustable parameters, this model accounts quantitatively for the very different KIE’s observed in the reactions of Ar+ and Kr+ with HD at low collision energies
Using the Balanced Scorecard: Both Common And Unique Measures Are Informative
The balanced scorecard (BSC), developed by Kaplan and Norton (1992), allows an organization to translate its strategy and objectives into a series of performance measures. A recent study by Lipe and Salterio (2000) found that subjects use common scorecard measures in performance evaluation but disregard unique measures. This study finds that both common and unique scorecard measures are used in performance evaluation
Gravitational polarization and the phenomenology of MOND
The modified Newtonian dynamics (MOND) has been proposed as an alternative to
the dark matter paradigm; the philosophy behind is that there is no dark matter
and we witness a violation of the Newtonian law of dynamics. In this article,
we interpret differently the phenomenology sustaining MOND, as resulting from
an effect of "gravitational polarization", of some cosmic fluid made of dipole
moments, aligned in the gravitational field, and representing a new form of
dark matter. We invoke an internal force, of non-gravitational origin, in order
to hold together the microscopic constituents of the dipole. The dipolar
particles are weakly influenced by the distribution of ordinary matter; they
are accelerated not by the gravitational field, but by its gradient, or tidal
gravitational field.Comment: 14 pages, 1 figure, to appear in Classical and Quantum Gravit
Ehrenfest dynamics is purity non-preserving: a necessary ingredient for decoherence
We discuss the evolution of purity in mixed quantum/classical approaches to
electronic nonadiabatic dynamics in the context of the Ehrenfest model. As it
is impossible to exactly determine initial conditions for a realistic system,
we choose to work in the statistical Ehrenfest formalism that we introduced in
Ref. 1. From it, we develop a new framework to determine exactly the change in
the purity of the quantum subsystem along the evolution of a statistical
Ehrenfest system. In a simple case, we verify how and to which extent Ehrenfest
statistical dynamics makes a system with more than one classical trajectory and
an initial quantum pure state become a quantum mixed one. We prove this
numerically showing how the evolution of purity depends on time, on the
dimension of the quantum state space , and on the number of classical
trajectories of the initial distribution. The results in this work open new
perspectives for studying decoherence with Ehrenfest dynamics.Comment: Revtex 4-1, 14 pages, 2 figures. Final published versio
Associations of Dwarf Galaxies
Hubble Space Telescope Advanced Cameras for Surveys has been used to
determine accurate distances for 20 galaxies from measurements of the
luminosity of the brightest red giant branch stars. Five associations of dwarf
galaxies that had originally been identified based on strong correlations on
the plane of the sky and in velocity are shown to be equally well correlated in
distance. Two more associations with similar properties have been discovered.
Another association is identified that is suggested to be unbound through tidal
disruption. The associations have the spatial and kinematic properties expected
of bound structures with 1 - 10 x 10^11 solar mass. However, these entities
have little light with the consequence that mass-to-light ratios are in the
range 100 - 1000 in solar units. Within a well surveyed volume extending to 3
Mpc, all but one known galaxy lies within one of the groups or associations
that have been identified.Comment: 50 pages, 2 tables, 15 encapsulated figures, 1 (3 part) jpg figure.
Submitted to Astronomical Journa
Binary Galaxies in the Local Supercluster and Its Neighborhood
We report a catalog of 509 pairs identified among 10403 nearby galaxies with
line-of-sight velocities V_LG < 3500 km/s.We selected binary systems in
accordance with two criteria (bounding and temporal), which require the
physical pair of galaxies to have negative total energy and its components to
be located inside the zero-velocity surface. We assume that individual galaxy
masses are proportional to their total K-band luminosities, M = L_K x 6M/L. The
catalog gives the magnitudes and morphological types of galaxies and also the
projected (orbital) masses and pair isolation indices. The component
line-of-sight velocity differences and projected distances of the binary
systems considered have power-law distributions with the median values of 35
km/s and 123 kpc, respectively. The median mass-to-K-band luminosity ratio is
equal to 11 M/L, and its uncertainty is mostly due to the errors of measured
velocities. Our sample of binary systems has a typical density contrast of d
ro/ro_c ~ 500 and a median crossing time of about 3.5 Gyr. We point out the
substantial fraction of binary systems consisting of late-type dwarf galaxies,
where the luminosities of both components are lower than that of the Small
Magellanic Cloud. The median projected distance for 41 such pairs is only 30
kpc, and the median difference of their line-of-sight velocities is equal to 14
km/s which is smaller than the typical error for radial-velocity (30 km/s).
This specific population of gas-rich dwarf binary galaxies such as I Zw 18 may
be at the stage immediately before merging of its components. Such objects,
which are usually lost in flux-limited (and not distance-limited) samples
deserve a thorough study in the HI radio line with high spatial and velocity
resolution.Comment: published in Astrophysical Bulletin, 2008, Vol. 63, No. 4, pp.
299-34
Complex Action Support from Coincidences of Couplings
Our model \cite{ownmMPP}\cite{SIMPP} with complex action in a functional
integral formulation with path integrals extending over all times, past and
future, is reviewed. Several numerical relations between coupling constants are
presented as supporting evidence. The new evidence is that some more
unexplained coincidences are explained in our model:
1) The "scale problem" is solved because the Higgs field expectation value is
predicted to be very small compared to say some fundamental scale, that might
be the Planck scale.
2) The Higgs VEV need not, however, to be just zero, but rather is predicted
to be so that the running top-Yukawa coupling just is about to be unity at this
scale; in this way the (weak) scale easily becomes "exponentially small".
Instead of the top-Yukawa we should rather say the highest flavour Yukawa
coupling here.
These predictions are only achieved by allowing the principle of minimization
of the imaginary part of the action SI(history) to to a certain extent adjust
some coupling constants in addition to the initial conditions.
If Susy-partners are not found in LHC, it would strengthen the need for
"solution" of the hierarchy or rather scale problem along the lines of the
present article.Comment: only text. Some printing mistakes corrected and a couple of new
subsections inserted and abstract stylistically changed a bi
Internal kinematics of spiral galaxies in distant clusters. Part II. Observations and data analysis
We have conducted an observing campaign with FORS at the ESO-VLT to explore
the kinematical properties of spiral galaxies in distant galaxy clusters. Our
main goal is to analyse transformation- and interaction processes of disk
galaxies within the special environment of clusters as compared to the
hierarchical evolution of galaxies in the field. Spatially resolved MOS-spectra
have been obtained for seven galaxy clusters at 0.3<z<0.6 to measure rotation
velocities of cluster members. For three of the clusters, Cl0303+17, Cl0413-65,
and MS1008-12, for which we presented results including a TF-diagram in Ziegler
et al. 2003, we describe here in detail the observations and data analysis.
Each of them was observed with two setups of the standard FORS MOS-unit.With
typical exposure times of >2 hours we reach an S/N>5 in the emission lines
appropriate for the deduction of the galaxies' internal rotation velocities
from [OII], Hbeta, or [OIII] profiles. Preselection of targets was done on the
basis of available redshifts as well as from photometric and morphological
information gathered from own observations, archive data, and from the
literature. Emphasis was laid on the definition of suitable setups to avoid the
typical restrictions of the standard MOS unit for this kind of observations. In
total we assembled spectra of 116 objects of which 50 turned out to be cluster
members. Position velocity diagrams, finding charts as well as tables with
photometric, spectral, and structural parameters of individual galaxies are
presented.Comment: 18 pages, 6 figures, accepted for publication in Astronomy and
Astrophysics. A version with full resolution figures can be downloaded from
http://www.uni-sw.gwdg.de/~vwgroup/publications.htm
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