58 research outputs found
Statistical Mechanics of Self--Gravitating System : Cluster Expansion Method
We study statistical mechanics of the self--gravitating system applying the
cluster expansion method developed in solid state physics. By summing infinite
series of diagrams, we derive a complex free energy whose imaginary part is
related to the relaxation time of the system. Summation of another series
yields two--point correlation function whose correlation length is essentially
given by the Jeans wavelength of the system.Comment: 4 pages including 2 eps figures, RevTe
Origin of scaling structure and non-gaussian velocity distribution in self-gravitating ring model
Fractal structures and non-Gaussian velocity distributions are characteristic
properties commonly observed in virialized self-gravitating systems such as
galaxies or interstellar molecular clouds. We study the origin of these
properties using the one-dimensional ring model which we newly propose in this
paper. In this simple model, particles are moving, on a circular ring fixed
in the three dimensional space, with mutual interaction of gravity. This model
is suitable for accurate symplectic integration method by which we find the
phase transition in this system from extended-phase to collapsed-phase through
an interesting phase (\halo-phase) which has negative specific heat. In this
intermediate energy scale, there appear scaling properties, non-thermal and
non-Gaussian velocity distributions. In contrast, these peculiar properties are
never observed in other \gas and \core phases. Particles in each phase have
typical time scales of motion determined by the cutoff length , the ring
radius and the total energy . Thus all relaxation patterns of the system
are determined by these three time scales.Comment: 21pages,11figure
Localization of dynamin 2 in rat seminiferous tubules during the spermatogenic cycle.
Dynamin is a protein essential to endocytosis. Dynamin 2, a dynamin isoform, is expressed most intensely in testicular tissue; however, precise localization has never been studied. Therefore, we investigated the expression of dynamin 2 in rat testicular tissue using immunohistochemical methods, and discuss here the physiological function of this protein. Testicular tissues were obtained from Wistar rats at 10, 21 and 63 days of age. Immunohistochemistrical examination and Western blot analysis were conducted using dynamin 2 specific antibody. Western blot analysis showed that expression in 21- and 63-day-old rats was more intense than that in 10-day-old rats. Dynamin 2 expression was observed using immunohistochemical method in the seminiferous tubules of all rats. In the 63-day-old rats, the expression was intense, especially in spermatids in the earlier maturation stages and in spermatocytes, and was observed in Sertoli cells. However, in spermatids, the expression gradually declined as spermatids matured to spermatozoa. In the 21-day-old rats, the expression was evident in spermatocytes and Sertoli cells, but that in the 10-day-old rats was weak. Intense expression of dynamin 2 during spermatogenesis suggests that this protein plays an important role in this process.</p
Onset of inflation in inhomogeneous cosmology
We study how the initial inhomogeneities of the universe affect the onset of
inflation in the closed universe. We consider the model of a chaotic inflation
which is driven by a massive scalar field. In order to construct an
inhomogeneous universe model, we use the long wavelength approximation ( the
gradient expansion method ). We show the condition of the inhomogeneities for
the universe to enter the inflationary phase.Comment: 22 pages including 12 eps figures, RevTe
Universal Non-Gaussian Velocity Distribution in Violent Gravitational Processes
We study the velocity distribution in spherical collapses and cluster-pair
collisions by use of N-body simulations. Reflecting the violent gravitational
processes, the velocity distribution of the resultant quasi-stationary state
generally becomes non-Gaussian. Through the strong mixing of the violent
process, there appears a universal non-Gaussian velocity distribution, which is
a democratic (equal-weighted) superposition of many Gaussian distributions (DT
distribution). This is deeply related with the local virial equilibrium and the
linear mass-temperature relation which characterize the system. We show the
robustness of this distribution function against various initial conditions
which leads to the violent gravitational process. The DT distribution has a
positive correlation with the energy fluctuation of the system. On the other
hand, the coherent motion such as the radial motion in the spherical collapse
and the rotation with the angular momentum suppress the appearance of the DT
distribution.Comment: 11 pages, 19 eps figures, RevTex, submitted to PRE, Revised version,
minor change
Local virial relation for self-gravitating system
We demonstrate that the quasi-equilibrium state in self-gravitating -body
system after cold collapse are uniquely characterized by the local virial
relation using numerical simulations. Conversely assuming the constant local
virial ratio and Jeans equation for spherically steady state system, we
investigate the full solution space of the problem under the constant
anisotropy parameter and obtain some relevant solutions. Especially, the local
virial relation always provides a solution which has a power law density
profile in both the asymptotic regions and . This type of
solutions observed commonly in many numerical simulations. Only the anisotropic
velocity dispersion controls this asymptotic behavior of density profile.Comment: 9 pages, 15 eps figures, RevTex, submitted to PR
Renormalization Group Approach to Einstein Equation in Cosmology
The renormalization group method has been adapted to the analysis of the
long-time behavior of non-linear partial differential equation and has
demonstrated its power in the study of critical phenomena of gravitational
collapse. In the present work we apply the renormalization group to the
Einstein equation in cosmology and carry out detailed analysis of
renormalization group flow in the vicinity of the scale invariant fixed point
in the spherically symmetric and inhomogeneous dust filled universe model.Comment: 16 pages including 2 eps figures, RevTe
Results of the search for inspiraling compact star binaries from TAMA300's observation in 2000-2004
We analyze the data of TAMA300 detector to search for gravitational waves
from inspiraling compact star binaries with masses of the component stars in
the range 1-3Msolar. In this analysis, 2705 hours of data, taken during the
years 2000-2004, are used for the event search. We combine the results of
different observation runs, and obtained a single upper limit on the rate of
the coalescence of compact binaries in our Galaxy of 20 per year at a 90%
confidence level. In this upper limit, the effect of various systematic errors
such like the uncertainty of the background estimation and the calibration of
the detector's sensitivity are included.Comment: 8 pages, 4 Postscript figures, uses revtex4.sty The author list was
correcte
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