839 research outputs found
Inflation from Superstring/M-Theory Compactification with Higher Order Corrections II -- Case of Quartic Weyl Terms --
We present a detailed study of inflationary solutions in M-theory with higher
order quantum corrections. We first exhaust all exact and asymptotic solutions
of exponential and power-law expansions in this theory with quartic curvature
corrections, and then perform a linear perturbation analysis around fixed
points for the exact solutions in order to see which solutions are more generic
and give interesting cosmological models. We find an interesting solution in
which the external space expands exponentially and the internal space is static
both in the original and Einstein frames. This may be regarded as moduli
stabilization by higher order corrections. Furthermore, we perform a numerical
calculation around this solution and find numerical solutions which give enough
e-foldings. We also briefly summarize similar solutions in type II
superstrings.Comment: 40 pages, 11 figures, v2: additional explanations, refs. added, to
appear in PR
Gravitational Wave Signals from Chaotic System: A Point Mass with A Disk
We study gravitational waves from a particle moving around a system of a
point mass with a disk in Newtonian gravitational theory. A particle motion in
this system can be chaotic when the gravitational contribution from a surface
density of a disk is comparable with that from a point mass. In such an orbit,
we sometimes find that there appears a phase of the orbit in which particle
motion becomes to be nearly regular (the so-called ``stagnant motion'') for a
finite time interval between more strongly chaotic phases. To study how these
different chaotic behaviours affect on observation of gravitational waves, we
investigate a correlation of the particle motion and the waves. We find that
such a difference in chaotic motions reflects on the wave forms and energy
spectra. The character of the waves in the stagnant motion is quite different
from that either in a regular motion or in a more strongly chaotic motion. This
suggests that we may make a distinction between different chaotic behaviours of
the orbit via the gravitational waves.Comment: Published in Phys.Rev.D76:024018,200
A computational scheme to evaluate Hamaker constants of molecules with practical size and anisotropy
We propose a computational scheme to evaluate Hamaker constants, , of
molecules with practical sizes and anisotropies. Upon the increasing
feasibility of diffusion Monte Carlo (DMC) methods to evaluate binding curves
for such molecules to extract the constants, we discussed how to treat the
averaging over anisotropy and how to correct the bias due to the
non-additivity. We have developed a computational procedure for dealing with
the anisotropy and reducing statistical errors and biases in DMC valuations,
based on possible validations on predicted . We applied the scheme to
cyclohexasilane molecule, SiH, used in 'printed electronics'
fabrications, getting [zJ], being in plausible range
supported even by other possible extrapolations. The scheme provided here would
open a way to use handy {\it ab initio} evaluations to predict wettabilities as
in the form of materials informatics over broader molecules.Comment: The manuscript was revised according to review comment
Overexpression of Adenylyl Cyclase 8 (AC8) in Mice Increases Intrinsic Heart Rate (IHR) and Reduces Heart Rate Variability (HRV), and Detaches HR and HRV from Autonomic Modulation
Relativistic stars with purely toroidal magnetic fields
We investigate the effects of the purely toroidal magnetic field on the
equilibrium structures of the relativistic stars. The master equations for
obtaining equilibrium solutions of relativistic rotating stars containing
purely toroidal magnetic fields are derived for the first time. To solve these
master equations numerically, we extend the Cook-Shapiro-Teukolsky scheme for
calculating relativistic rotating stars containing no magnetic field to
incorporate the effects of the purely toroidal magnetic fields. By using the
numerical scheme, we then calculate a large number of the equilibrium
configurations for a particular distribution of the magnetic field in order to
explore the equilibrium properties. We also construct the equilibrium sequences
of the constant baryon mass and/or the constant magnetic flux, which model the
evolution of an isolated neutron star as it loses angular momentum via the
gravitational waves. Important properties of the equilibrium configurations of
the magnetized stars obtained in this study are summarized as follows ; (1) For
the non-rotating stars, the matter distribution of the stars is prolately
distorted due to the toroidal magnetic fields. (2) For the rapidly rotating
stars, the shape of the stellar surface becomes oblate because of the
centrifugal force. But, the matter distribution deep inside the star is
sufficiently prolate for the mean matter distribution of the star to be
prolate. (3) The stronger toroidal magnetic fields lead to the mass-shedding of
the stars at the lower angular velocity. (4) For some equilibrium sequences of
the constant baryon mass and magnetic flux, the stars can spin up as they lose
angular momentum.Comment: 13 figures, 7 tables, submitted to PR
Equilibrium Configurations of Strongly Magnetized Neutron Stars with Realistic Equations of State
We investigate equilibrium sequences of magnetized rotating stars with four
kinds of realistic equations of state (EOSs) of SLy (Douchin et al.), FPS
(Pandharipande et al.), Shen (Shen et al.), and LS (Lattimer & Swesty).
Employing the Tomimura-Eriguchi scheme to construct the equilibrium
configurations. we study the basic physical properties of the sequences in the
framework of Newton gravity. In addition we newly take into account a general
relativistic effect to the magnetized rotating configurations. With these
computations, we find that the properties of the Newtonian magnetized stars,
e.g., structure of magnetic field, highly depends on the EOSs.
The toroidal magnetic fields concentrate rather near the surface for Shen and
LS EOSs than those for SLy and FPS EOSs. The poloidal fields are also affected
by the toroidal configurations. Paying attention to the stiffness of the EOSs,
we analyze this tendency in detail. In the general relativistic stars, we find
that the difference due to the EOSs becomes small because all the employed EOSs
become sufficiently stiff for the large maximum density, typically greater than
. The maximum baryon mass of the magnetized stars
with axis ratio increases about up to twenty percents for that of
spherical stars. We furthermore compute equilibrium sequences at finite
temperature, which should serve as an initial condition for the hydrodynamic
study of newly-born magnetars. Our results suggest that we may obtain
information about the EOSs from the observation of the masses of magnetars.Comment: submitted to MNRA
The sixth Painleve equation arising from D_4^{(1)} hierarchy
The sixth Painleve equation arises from a Drinfel'd-Sokolov hierarchy
associated with the affine Lie algebra of type D_4 by similarity reduction.Comment: 14 page
Gravitational Waves from Chaotic Dynamical System
To investigate how chaos affects gravitational waves, we study the
gravitational waves from a spinning test particle moving around a Kerr black
hole, which is a typical chaotic system. To compare the result with those in
non-chaotic dynamical system, we also analyze a spinless test particle, which
orbit can be complicated in the Kerr back ground although the system is
integrable. We estimate the emitted gravitational waves by the multipole
expansion of a gravitational field. We find a striking difference in the energy
spectra of the gravitational waves. The spectrum for a chaotic orbit of a
spinning particle, contains various frequencies, while some characteristic
frequencies appear in the case of a spinless particle.Comment: 8 pages, 13 figures. submitted to PR
Profiling ascidian promoters as the primordial type of vertebrate promoter
<p>Abstract</p> <p>Background</p> <p>CpG islands are observed in mammals and other vertebrates, generally escape DNA methylation, and tend to occur in the promoters of widely expressed genes. Another class of promoter has lower G+C and CpG contents, and is thought to be involved in the spatiotemporal regulation of gene expression. Non-vertebrate deuterostomes are reported to have a single class of promoter with high-frequency CpG dinucleotides, suggesting that this is the original type of promoter. However, the limited annotation of these genes has impeded the large-scale analysis of their promoters.</p> <p>Results</p> <p>To determine the origins of the two classes of vertebrate promoters, we chose <it>Ciona intestinalis</it>, an invertebrate that is evolutionarily close to the vertebrates, and identified its transcription start sites genome-wide using a next-generation sequencer. We indeed observed a high CpG content around the transcription start sites, but their levels in the promoters and background sequences differed much less than in mammals. The CpG-rich stretches were also fairly restricted, so they appeared more similar to mammalian CpG-poor promoters.</p> <p>Conclusions</p> <p>From these data, we infer that CpG islands are not sufficiently ancient to be found in invertebrates. They probably appeared early in vertebrate evolution via some active mechanism and have since been maintained as part of vertebrate promoters.</p
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