471 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
Strong Gravitational Lensing and Velocity Function as Tools to Probe Cosmological Parameters: Current Constraints and Future Predictions
Constraints on cosmological models from strong gravitational lensing
statistics are investigated. We pay particular attention to the role of the
velocity function in the calculation of the lensing probability. The velocity
function derived from the observed galaxy luminosity function, which is used in
most previous work, is unable to predict the large separation lensing events.
In this paper, we also use the Press-Schechter theory to construct a velocity
function theoretically. Model predictions are compared with the observed
velocity function and the HST snapshot survey. Comparison with the latter
observation shows that the predictions based on the theoretical velocity
function are consistent with the observed large separation events in COBE
normalized low-density models, especially with a non-vanishing cosmological
constant. Adopting the COBE normalization, however, we could find no model
which simultaneously satisfies both the observed velocity function and the HST
snapshot survey. We systematically investigate various uncertainties in the
gravitational lensing statistics including finite core radius, the distance
formula, magnification bias, and dust obscuration. The results are very
sensitive to these effects as well as theoretical models for the velocity
function, implying that current limits on the cosmological parameters should be
interpreted with caution. Predictions for future surveys are also presented.Comment: 27 pages, 8 figures, ptptex. Progress of Theoretical Physics, in
pres
Anti-cancer Approach with NK4 and Anti-angiogenic Mechanism of NK4: Inhibition of Endothelial Fibronectin Assembly and Colon Cancer Metastasis
Division of Tumor Dynamics and Regulatio
Anti-cancer Approach with NK4 and Anti-angiogenic Mechanism of NK4: NK4 Gene Therapy for Malignant Mesothelioma
Division of Tumor Dynamics and Regulatio
Suppression of Met/HGF Receptor Activation by the Met Juxtamembrane Function and Cell-Cell Contact
Division of Tumor Dynamics and Regulatio
Black Hole Binary Formation in the Expanding Universe --- Three Body Problem Approximation ---
We study black hole MACHO binary formation through three-body interactions in
the early universe at s. The probability distribution functions
of the eccentricity and the semimajor axis of binaries as well as of the
coalescence time are obtained assuming that the black holes are randomly formed
in space. We confirm that the previous order-of-magnitude estimate for the
binary parameters is valid within error. We find that the
coalescence rate of the black hole MACHO binaries is events/year/galaxy taking into consideration several possible
factors which may affect this estimate. This suggests that the event rate of
coalescing binary black holes will be at least several events per year within
15 Mpc. The first LIGO/VIRGO interferometers in 2001 will be able to verify
whether the MACHOs are black holes or not.Comment: Revtex, 25 pages, 10 figures, to appear in PR
Equation of state in the PNJL model with the entanglement interaction
The equation of state and the phase diagram in two-flavor QCD are
investigated by the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model
with an entanglement vertex between the chiral condensate and the
Polyakov-loop. The entanglement-PNJL (EPNJL) model reproduces LQCD data at zero
and finite chemical potential better than the PNJL model. Hadronic degrees of
freedom are taken into account by the free-hadron-gas (FHG) model with the
volume-exclusion effect due to the hadron generation. The EPNJL+FHG model
improves agreement of the EPNJL model with LQCD data particularly at small
temperature. The quarkyonic phase survives, even if the correlation between the
chiral condensate and the Polyakov loop is strong and hadron degrees of freedom
are taken into account. However, the location of the quarkyonic phase is
sensitive to the strength of the volume exclusion.Comment: 9 pages, 7 figure
Small localized black holes in a braneworld: Formulation and numerical method
No realistic black holes localized on a 3-brane in the Randall-Sundrum
infinite braneworld have been found so far. The problem of finding a static
black hole solution is reduced to a boundary value problem. We solve it by
means of a numerical method, and show numerical examples of a localized black
hole whose horizon radius is small compared to the bulk curvature scale. The
sequence of small localized black holes exhibits a smooth transition from a
five-dimensional Schwarzschild black hole, which is a solution in the limit of
small horizon radius. The localized black hole tends to flatten as its horizon
radius increases. However, it becomes difficult to find black hole solutions as
its horizon radius increases.Comment: RevTeX, 13 pages, 6 figures, references corrected, typos corrected;
to appear in Phys.Rev.
Exact Wave Propagation in a Spacetime with a Cosmic String
We present exact solutions of the massless Klein-Gordon equation in a
spacetime in which an infinite straight cosmic string resides. The first
solution represents a plane wave entering perpendicular to the string
direction. We also present and analyze a solution with a static point-like
source. In the short wavelength limit these solutions approach the results
obtained by using the geometrical optics approximation: magnification occurs if
the observer lies in front of the string within a strip of angular width , where is the string tension. We find that when the distance from
the observer to the string is less than , where is the
wave length, the magnification is significantly reduced compared with the
estimate based on the geometrical optics due to the diffraction effect. For
gravitational waves from neutron star(NS)-NS mergers the several lensing events
per year may be detected by DECIGO/BBO.Comment: 15 pages, 8 figures, reference adde
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