6,913 research outputs found
Various Approaches to Cosmological Gravitational Lensing in Inhomogeneous Models
Gravitational lensing of distant objects caused by gravitational tidal forces
from inhomogeneities in the universe is weak in most cases, but it is noticed
that it gives a great deal of information about the universe, especially
regarding the distribution of dark matter. The statistical values of optical
quantities such as convergence, amplification and shear have been derived by
many people using various approaches, which include the linear perturbational
treatment in the weak limit and the nonlinear treatment considering small-scale
matter distribution.
In this review paper we compare the following three main approaches: (a) the
approach in the multi-lens-plane theory; (b) the approach due to the direct
integration method; and (c) the perturbational approach.
In the former two approaches inhomogeneous matter distributions are produced
in the CDM model using -body simulations (the PM code and the tree-code,
respectively). In (c) the power spectrum corresponding to the CDM model is used
for the large-scale matter distribution.Comment: 30 pages, 13 figure
Quantum information with Gaussian states
Quantum optical Gaussian states are a type of important robust quantum states
which are manipulatable by the existing technologies. So far, most of the
important quantum information experiments are done with such states, including
bright Gaussian light and weak Gaussian light. Extending the existing results
of quantum information with discrete quantum states to the case of continuous
variable quantum states is an interesting theoretical job. The quantum Gaussian
states play a central role in such a case. We review the properties and
applications of Gaussian states in quantum information with emphasis on the
fundamental concepts, the calculation techniques and the effects of
imperfections of the real-life experimental setups.
Topics here include the elementary properties of Gaussian states and relevant
quantum information device, entanglement-based quantum tasks such as quantum
teleportation, quantum cryptography with weak and strong Gaussian states and
the quantum channel capacity, mathematical theory of quantum entanglement and
state estimation for Gaussian states.Comment: 170 pages. Minors of the published version are corrected and listed
in the Acknowledgement part of this versio
Optical and CO Radio Observations of Poor Cluster Zwicky 1615.8+3505
The cluster Zwicky 1615.8+3505 is considered to be a dynamically young poor
cluster. To investigate the morphology and star-formation activity of galaxies
under the environment of a dynamically young poor cluster, we have performed V,
R, and I surface photometry, optical low-resolution spectroscopy, and 12CO
(J=1-0) line observations for member galaxies. Our data show that more than 90%
of the observed galaxies show regular morphologies and no star-formation
activities, indicating that the environment does not affect these galaxy
properties. Among sixteen galaxies observed, only NGC 6104 shows a significant
star-formation activity, and shows a distorted morphology, indicating a tidal
interaction. This galaxy contains double knots, and only one knot possesses
Seyfert activity, though the sizes and luminosities are similar to each other;
we also discuss this feature.Comment: LaTeX manuscript (text.tex, use PASJ style files), four PS figures
(fig[a-d].ps), and three PASJ style files. text.tex, figb.ps, and figd.ps are
up-dated. To be appeared in The Publications of the Astronomical Society of
Japan, Vol. 51, No. 3 (1999 June issue
Iterative Approach to Gravitational Lensing Theory
We develop an iterative approach to gravitational lensing theory based on
approximate solutions of the null geodesic equations. The approach can be
employed in any space-time which is ``close'' to a space-time in which the null
geodesic equations can be completely integrated, such as Minkowski space-time,
Robertson-Walker cosmologies, or Schwarzschild-Kerr geometries. To illustrate
the method, we construct the iterative gravitational lens equations and time of
arrival equation for a single Schwarzschild lens. This example motivates a
discussion of the relationship between the iterative approach, the standard
thin lens formulation, and an exact formulation of gravitational lensing.Comment: 27 pages, 2 figures, submitted to Phys.Rev.D, minor revisions, new
reference
Enhancement of the Critical Current Density of YBa2Cu3Ox Superconductors under Hydrostatic Pressure
The dependence of the critical current density Jc on hydrostatic pressure to
0.6 GPa is determined for a single 25-degree [001]-tilt grain boundary in a
bicrystalline ring of nearly optimally doped melt-textured YBa2Cu3Ox. Jc is
found to increase rapidly under pressure at +20 %/GPa. A new diagnostic method
is introduced (pressure-induced Jc relaxation) which reveals a sizeable
concentration of vacant oxygen sites in the grain boundary region. Completely
filling such sites with oxygen anions should lead to significant enhancements
in Jc.Comment: revised manuscript, graphic errors in figures correcte
Photometric Observations of Star Formation Activity in Early Type Spirals
We observationally study the current star formation activities of early type
spiral galaxies. We construct a complete sample of 15 early type spirals having
far-infrared (FIR) to optical B band luminosity ratios, L(FIR)/L(B), larger
than the average of the type, and make their CCD imaging of the R and H-alpha
bands. The equivalent widths of H-alpha emission increase with increasing
L(FIR)/L(B), indicating that L(FIR)/L(B) can be an indicator of star formation
for such early type spirals with star formation activities higher than the
average. For all of the observed early type spirals, the extended HII regions
exist at the central regions with some asymmetric features. H-alpha emission is
more concentrated to the galactic center than the R band light, and the degree
of the concentration increases with the star formation activity. We also
analyze the relation between the star formation activities and the existence of
companion galaxies in the sample galaxies and other bright early type spirals.
No correlation is found and this suggests that the interaction is not
responsible for all of the star formation activities of early type spirals.Comment: LaTex, 23 pages (2 tables included), plus 9 Postscript figures & 1
table. To be published in AJ (November issue
New Physics and CP Angles Measurement at B Factory
We have analyzed how much the angles to be measured at B factories can
deviate from the geometrical ones defined in unitarity triangle under the
existence of new physics. The measurements are given in rephasing invariant
form. If KM matrix is not a and unitary matrix, and
is affected, and the value of depends on the
decay mode. The deviation is constrained to be less than the experimental
precision attained in the next decade by the available data of the magnitude of
KM matrix elements. Deviation of the sum of three angles from cannot be
detected unless new physics contributes significantly to decay or meson
system.Comment: 11 pages, 1 figure in eps format, LaTeX, epsfig.st
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