| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| I26-01 |
Sumio |
Yamada |
Mathematical Institute Tohoku University |
Riemannian geometric aspects of Penrose-type inequalities |
| Abstract |
|
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| I26-02 |
Mu-Tao |
Wang |
Colombia University |
Quasilocal mass in general relativity |
| Abstract |
|
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-01 |
Kunihito |
Uzawa |
Department of Physics Kinki University |
Warped de Sitter compactifications |
| Abstract |
We show that the warped de Sitter compactification is possible under certain
conditions in D-dimensional gravitational theory coupled to a dilaton;
a form field strength; and a cosmological constant. We find that the solutions
of field equations give de Sitter spacetime with the warped structure.
We also discuss the dynamics of moduli in the lower-dimensional effective
theories and show that the internal space moduli can be fixed by the flux
if the indices of non-vanishing components of the field strength could
be along the internal space. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-02 |
Cristián |
Martínez |
Centro de Estudios Cientificos (CECS) |
Exact solutions of Einstein gravity with a negative cosmological constant
coupled to a massless scalar field in arbitrary spacetime dimensions |
| Abstract |
We present new exact solutions of Einstein gravity with a negative cosmological
constant coupled to a massless scalar field in arbitrary spacetime dimensions.
The spacetimes are supposed to be a warped product M_2 x K^(n-2); where
K^(n-2) is a (n-2)-dimensional Einstein space with sectional curvature
k=-1;0;1. For the case k=0; we find an exact solution which is the generalization
of Xanthopoulos-Zannias spacetime in presence of a negative cosmological
constant and of a Ricci flat base manifold. The solution exhibits a naked
singularity unless the scalar field vanishes. In the cases of nonvanishing
sectional curvature; asymptotic solutions are presented. In all the cases
the solutions are asymptotically locally anti-de Sitter spacetimes. The
mass of these spacetimes is computed using the Hamiltonian formalism via
the Regge-Teitelboim approach. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-03 |
Teruaki |
Suyama |
Research Center for the Early Universe The University of Tokyo |
Black hole perturbation in parity violating gravitational theories |
| Abstract |
We study linear perturbations around the static and spherically symmetric
spacetime for the gravitational theories whose Lagrangian depends on Ricci
scalar and the parity violating Chern-Simons term. By an explicit construction;
we show that Hamiltonian for the perturbation variables is not bounded
from below in general; suggesting that such a background spacetime is unstable
against perturbations. This gives a strong limit on a phenomenological
gravitational model which violates parity. We also provide a necessary
and sufficient condition for the theory to belong to a special class in
which no such instability occurs. For such theories; the number of propagating
modes for $\ell \ge 2$ is three; one from the odd and the other two from
the even. Unlike in the case of $f(R)$ theories; those modes are coupled
each other; which can be used as a distinctive feature to test the parity
violating theories from observations. All the modes propagate at the speed
of light. No-ghost condition and no-tachyon condition are the same as those
in $f(R)$ theories. For the dipole perturbations; the odd and the even
modes completely decouple. The odd mode gives a slowly-rotating BH solution
whose metric is linearized in its angular momentum. We provide an integral
expression of such a solution. On the other hand; the even mode propagates
at the speed of light. For the monopole perturbation; in addition to a
mode which just shifts the mass of the background BH; there is also one
even mode that propagates at the speed of light. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-04 |
Sergey |
Pavluchenko |
Special Astrophysical Observatory of the Russian Academy of Sciences |
New features of black hole solutions in f(R; G) theories |
| Abstract |
Our report reflects new features of the black-hole (BH)-like (spherically-symmetric)
solutions in f(R; G) theories. Since BH-like solutions are an important
tool for testing GR; it might be the same for the generalizations of GR
and f(R;G) theories are one of the best candidate for it. So we report
our findings for BH-like solutions for several partial cases of f(R; G)
theories as well as we attempt to construct generic solution and find out
its properties. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-05 |
Keiki |
Saito |
SOKENDAI |
The high frequency limit in f(R) gravity |
| Abstract |
In the general relativity; the effective gravitational stress energy tensor
which is caused by the backreaction of short wavelength perturbations acts
the gravitational wave. We derive the effective gravitational stress energy
tensor in f(R) gravity; and investigate the property of this stress energy
tensor. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-06 |
Hayato |
Motohashi |
Research center for the early universe University of Tokyo |
The unification of inflation and dark energy in extended f(R) gravity |
| Abstract |
We have considered the theoretical unification of two regimes of accelerated
expansion in the early Universe and the late time Universe in f(R) gravity.
The problem is that Ricci scalar can be negative at the end of R^2 inflation
because conventional f(R) functions do not satisfy viability conditions
for negative Ricci scalar. We have constructed viable f(R) models for negative
R. We have also performed numerical calculation and found that there exists
characteristic anharmonic oscillation. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-07 |
Ahmet |
Gumrukcuoglu |
IPMU University of Tokyo |
Nonlinear perturbations in the IR limit of Horava-Lifshitz gravity |
| Abstract |
The power-counting renormalizable theory of gravitation; proposed by Horava;
has attracted significant attention. The anisotropic scaling between space
and time has interesting implications for cosmology. In the projectable
version of the theory; the lack of a local Hamiltonian constraint gives
rise to a built-in dark matter-like component; as well as an additional
scalar degree of freedom. Although in the UV; this component has very simple
dynamics and is coupled weakly; a major problem arises in the IR limit
where the scalar graviton becomes strongly coupled. While the perturbative
expansion is breaking down; it has been shown recently that the nonlinear
solution for vacuum Friedman Robertson Walker universe is regular in this
limit. We extend this analysis to include matter fields and show that the
theory is continuously connected to general relativity coupled to the dark
matter-like component at low energies. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-08 |
Naoki |
Tsukamoto |
Rikkyo University |
There are no stationary axisymmetric star solutions in Horava-Lifshitz
gravity |
| Abstract |
We discuss rotating stars in Horava-Lifshitz gravity. In the stationary
axisymmetric spacetime; we show the momentum conversation is not fulfilled
under the assumption that the star is filled with perfect fluid; that the
energy density is a piecewise-continuous; non-negative function of the
pressure; and that the pressure at the center of the star is positive.
As a result; we find that there are no stationary axisymmetric star solutions
in Horava-Lifshitz gravity. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-09 |
Seiju |
Ohashi |
Kyoto University |
Spherical collapse of inhomogeneous dust cloud in the Lovelock theory |
| Abstract |
We study gravitational collapse of spherically symmetric inhomogeneous
dust cloud in the Lovelock theory without cosmological constant. We show
that the final fate of gravitational collapse in this theory depends on
the spacetime dimensions. In odd dimensions the naked singularities formed
are found to be massive. In the even dimensions; on the other hand; the
naked singularities are found to be massless. We also show that the curvature
strength of naked singularity is independent of the spacetime dimensions
in odd dimensions. However; it depends on the spacetime dimensions in even
dimension. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-10 |
Kent |
Yagi |
Department of Physics Kyoto University |
Binary Inspiral in Quadratic Gravity |
| Abstract |
We consider a general class of quantum gravity-inspired theories; where
the Einstein-Hilbert action is extended through the addition of all terms
quadratic in the curvature tensor coupled to scalar field. This class of
theories includes Einstein-Dilaton-Gauss-Bonnet (EDGB) and dynamical Chern-Simons
(CS) gravity. We consider scalar and gravitational radiation from black
hole binaries under this theory. We analytically solve the wave equations
for the scalar and gravitational radiation in the post-Newtonian formalism
and estimate the energy flux correction. Then; we estimate the expected
constraint on this theory from ground-based advanced gravitational wave
detectors. We found that we can put considerably stronger constraints on
EDGB and CS theories compared to the current solar system experiments. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-11 |
Takayuki |
Suzuki |
Yamaguchi University Kiyoshi Shiraishi's laboratory |
N-body simulation of cosmic structure formation on the MOffat Gravity |
| Abstract |
MOG is abbreviated name for MOdified Gravity developed by John Moffat(2005).It
also called Scalr Tensor Vector gravity(STVG). It's added repulsive fifth
force by the vector field to a gravity theory. MOG produces a Yukawa-like
modification of the gravitational force. Intuitively; this result can be
described as follows: far from a source gravity is stronger than the Newtonian
prediction; but at shorter distances; it is counteracted by a repulsive
fifth force due to the vector field. It can explain a galactic rotary curve
and the cosmic structure formation without dark matter.However;these are
claims of the developer and his collaboraters. And;these studies are by
simple approximate calculation. Therefore it needs objective verifications
precisely. On this study;the cosmic structure formation is calculated based
on the gravity acceleration equation of MOG.The purpose of my study is
verification of MOG from the viewpoint of N-body simulation. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O26-12 |
Kazuharu |
Bamba |
Kobayashi-Maskawa Institute for the Origin of Particles and the Universe
Nagoya University |
Screening scenario for cosmological constant in de Sitter solutions; phantom-divide
crossing and finite-time future singularities in non-local gravity |
| Abstract |
We investigate de Sitter solutions in non-local gravity as well as in non-local
gravity with Lagrange constraint multiplier. We examine a condition to
avoid a ghost and discuss a screening scenario for a cosmological constant
in de Sitter solutions. Furthermore; we explicitly demonstrate that three
types of the finite-time future singularities can occur in non-local gravity
and explore their properties. In addition; we evaluate the effective equation
of state for the universe and show that the late-time accelerating universe
may be effectively the quintessence; cosmological constant or phantom-like
phases. In particular; it is found that there is a case in which a crossing
of the phantom divide from the non-phantom (quintessence) phase to the
phantom one can be realized when a finite-time future singularity occurs.
Moreover; it is demonstrated that the addition of an $R^2$ term can cure
the finite-time future singularities in non-local gravity. It is also suggested
that in the framework of non-local gravity; adding an $R^2$ term leads
to possible unification of the early-time inflation with the late-time
cosmic acceleration. Reference: Kazuharu Bamba; Shin'ichi Nojiri; Sergei
D. Odintsov and Misao Sasaki; ``Screening of cosmological constant for
De Sitter Universe in non-local gravity; phantom-divide crossing and finite-time
future singularities;'' arXiv:1104.2692 [hep-th]. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| I27-01 |
Shoji |
Asai |
University of Tokyo |
The latest results of LHC - Hint of Higgs and Dark matter |
| Abstract |
|
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| I27-02 |
Pau |
Figueras |
University of Cambridge |
Braneworld black holes |
| Abstract |
|
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O27-01 |
Umpei |
Miyamoto |
Department of Physics Rikkyo University |
Astrophysical censorship |
| Abstract |
There are several solutions to the Einstein equation exhibiting naked-singularity
formation in gravitational collapse; which could possibly serve as counterexamples
to the cosmic censor hypothesis. It has not been examined seriously; however;
whether or not such naked singularities are indeed visible to asymptotic
observers in astrophysically realistic stellar collapse; such as the core
collapse and the delayed collapse in the final stage of its evolution.
In this paper; we set the spherically symmetric mass distribution which
is motivated by the astrophysical scenarios and evolve it with vanishing
pressure for simplicity. We show that even if a naked singularity could
appear at the centre; the naked singularity is hidden behind an event horizon
and cannot be observed by a distant observer. With this illustration; we
argue the existence of an ``astrophysical censor'' that prohibits singularities
formed in astrophysical gravitational collapse from being observed by a
distant observer. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O27-02 |
Soichiro |
Isoyama |
Kyoto university YITP |
Cosmic censorship in overcharging a charged black hole with a charged particle. |
| Abstract |
Despite a widespread belief; it was claimed that a nearly extremal charged
non-rotating black hole could be overcharged by capturing charged test
particles; which seems to imply the possible violation of the cosmic censorship.
However; the analysis of this claim is not conclusive because the effects
of radiative energy loss and self-force on the motion of a charged particle
have not been considered. We found that these effects can be properly taken
into account when the particle orbit is chosen at the border between plunge
and bounce cases. By analyzing this marginal orbit in detail; we conclude
that a charged non-rotating black hole cannot be overcharged by absorbing
a charged particle because of the backreaction effect. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O27-03 |
Tomohiro |
Harada |
Rikkyo University |
High-velocity collision of particles around a rapidly rotating black hole |
| Abstract |
We derive a general formula for the center-of-mass (CM) energy for the
near-horizon collision of two general geodesic particles around a Kerr
black hole. We find that if the angular momentum of the particle satisfies
the critical condition; the CM energy can be arbitrarily high. We then
apply the formula to the collision of a particle orbiting an innermost
stable circular orbit (ISCO) and another generic particle near the horizon
and find that the CM energy is arbitrarily high if we take the maximal
limit of the black hole spin. In view of the astrophysical significance
of the ISCO; this implies that particles can collide around a rapidly rotating
black hole with a very high CM energy without any artificial fine-tuning.
We next apply the formula to the collision of general inclined geodesic
particles and show that; in the direct collision scenario; the collision
with an arbitrarily high CM energy can occur near the horizon of maximally
rotating black holes not only at the equ ator but also on a belt centered
at the equator between latitudes $\pm 42.94^{\circ}$. This is also true
in the scenario through the collision of a last stable orbit particle.
This strongly suggests that if signals due to high-energy collision are
to be observed; such signals will be generated primarily on this belt. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O27-04 |
Hirotaka |
Yoshino |
KEK |
Bosenova collapse of axion cloud around a rotating black hole |
| Abstract |
It was pointed out by Arvanitaki et al. that the string theory implies
the existence of many ultralight massive particles (stringy axions) in
addition to the QCD axion. These axions have possibility to cause many
interesting phenomena in cosmology and astrophysics. One of them is the
superradiant instability of axion cloud around a rotating astrophysical
black hole. In particular; the nonlinear effect of axions may cause violent
phenomena called "bosenova" which is analogous to the explosive
phenomena of Bose-Einstein condensates observed in experiments. We performed
three-dimensional numerical simulations of the axion field around a Kerr
black hole; and showed that the bosenova collapse actually happens in this
system. In this talk; we would like to introduce our simulations and discuss
their observational consequences. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O27-05 |
Ryo |
Saito |
Yukawa Institute for Theoretical Physics Kyoto University |
Constraints on Particle Dark Matter Models by the Presence of Primordial
Black Holes |
| Abstract |
We investigate constraints on particle dark matter models when primordial
black holes exist as a fraction of the dark matter in the Universe. The
primordial black holes attract the surrounding particle dark matter and
increase their abundance around them. We estimate consequent enhancement
of the annihilation rate and cosmic ray signals; and give constraints on
the particle dark matter models by the cosmic ray experiments in the presence
of primordial black holes. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O27-06 |
Kentaro |
Takami |
Max-Planck-Institute for Gravitational Physics Albert-Einstein-Institute |
A quasi-radial stability criterion for rotating relativistic stars |
| Abstract |
The stability properties of relativistic stars against gravitational collapse
to black holes is a classical problem in general relativity. In 1988; a
sufficient criterion for secular instability was established by Friedman;
Ipser & Sorkin; who proved that a sequence of uniformly rotating barotropic
stars are secularly unstable on one side of a turning point and then argued
that a stronger result should hold: that the sequence should be stable
on the opposite side; with the turning point marking the onset of secular
instability. We show here that this expectation is not met. By computing
in full general relativity the F-mode frequency for a large number of rotating
stars; we show that the neutral-stability point; that is; where the frequency
becomes zero; differs from the turning point for rotating stars. Using
numerical simulations; we validate that the new criterion can be used to
assess the dynamical stability of relativistic rotating stars. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O27-07 |
Hajime |
Sotani |
National Astronomical Observatory of Japan |
Effect of Pasta Phase on Oscillations in Neutron Stars |
| Abstract |
We show that the shear modes in the neutron star crust are quite sensitive
to the existence of nonuniform nuclear structures; so-called ``pasta".
Due to the existence of pasta phase; the frequencies of shear modes are
reduced; where the dependence of fundamental frequency is different from
that of overtones. Since the torsional shear frequencies depend strongly
on the structure of pasta phase; through the observations of stellar oscillations;
one can probe the pasta structure in the crust; although that is quite
difficult via the other observations. Additionally; considering the effect
of pasta phase; we show the possibility to explain the all observed frequencies
in the SGR 1806-20 with using only crust torsional shear modes. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O27-08 |
Motoyuki |
Saijo |
Department of Physics Rikkyo University |
Dynamical Approaches for Secular Instabilities in Rotating Stars |
| Abstract |
We investigate the secular instability of rotating stars in dynamical approach.
In general; the existence of the physics varies in dynamical timescale
prohibit us to reach secular timescale in dynamical approach. Here we impose
an approximation of neglecting the acoustic waves; and focus on the physics
varies in secular timescale. We particularly focus on r-mode instability;
and investigate its dynamical property. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O27-09 |
Takashi |
Tamaki |
Department of Physics General Education College of Engineering Nihon University |
What are universal features of gravitating Q-balls? |
| Abstract |
We investigate how gravity affects Q-balls by exemplifying the case of
the Affleck-Dine potential. Surprisingly; stable Q-balls with arbitrarily
small charge exist; no matter how weak gravity is; contrary to the case
of flat spacetime. We also show analytically that this feature holds true
for general models as long as the leading order term of the potential is
a positive mass term in its Maclaurin series. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| I28-01 |
Eiichiro |
Komatsu |
University of Texas at Austin |
Cosmology in the Next Decade |
| Abstract |
|
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| I28-02 |
Nicolás |
Yunes |
Massachusetts Institute of Technology |
Gravitational Waves from Compact Binaries as Probes of the Universe |
| Abstract |
|
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-01 |
Takuya |
Tsuchiya |
Waseda University |
Constraint propagation and constraint-damping for C^2-adjusted formulations |
| Abstract |
In order to perform accurate and stable long-term numerical calculations;
we construct new sets of ADM and BSSN evolution equations by adjusting
constraints to their right-hand-sides. We applied a method suggested by
Fiske (2004); which adds functional derivative of norm of constraints;
C^2. We derived their constraint propagation equations (evolution equations
of constraints) in flat spacetime; which show that C^2 itself evolve decaying.
We also perform actual numerical tests in the gauge-wave and the polarized
Gowdy-wave testbeds; and show the constraint-damping appears. The life-time
of the standard BSSN simulations is improved at least 10 times longer in
gauge-wave evolution test. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-02 |
Yuichiro |
Sekiguchi |
Yukawa Institute for Theoretical Physics Kyoto University |
Effects of hyperon in binary neutron star mergers |
| Abstract |
Numerical simulations for the merger of binary neutron stars are performed
in full general relativity incorporating nucleonic and hyperonic finite-temperature
equation of state (EOS) and neutrino cooling for the first time. It is
found that even for the hyperonic EOS; a hypermassive neutron star is first
formed after the merger for the typical mass $\approx 2.7 M_\odot$; and
subsequently collapses to a black hole (BH). It is shown that hyperons
play substantial role in the post-merger dynamics; torus formation around
the BH; and emission of the gravitational waves (GWs). In particular; the
emergence of the hyperons is imprinted in GWs. Therefore; GW observations
will provide a potential opportunity to explore the composition of the
neutron star matter. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-03 |
Kenta |
Hotokezaka |
Kyoto University |
Gravitational waves from binary neutron star mergers: measuring of the
equation of state |
| Abstract |
We study the dependence of the dynamical behavior of mergers of binary
neutron stars and resulting gravitational waveforms on the equation of
state of the supernuclear-density matter. For this purpose; we perform
numerical-relativity simulations for the merger of a binary neutron star
with 6 nuclear-theory-based equations of state (EOSs). We show gravitational
waves carry information of the merger process; the tidal deformation of
neutron stars; and the remnant. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-04 |
Kenta |
Kiuchi |
Yukawa Institute for Theoretical Physics Kyoto University Kyoto 606-8502
Japan |
Gravitational waves and neutrino emission from the merger of binary neutron
stars |
| Abstract |
Numerical simulations for the merger of binary neutron stars are performed
in full general relativity incorporating a finite-temperature (Shen's)
equation of state (EOS) and neutrino cooling for the first time. It is
found that for this stiff EOS; a hypermassive neutron star (HMNS) with
a long lifetime ($\gg 10$ ms) is the outcome for the total mass $\alt 3.0M_{\odot}$.
It is shown that the typical total neutrino luminosity of the HMNS is $\sim
3$--$ 8\times 10^{53}$~erg/s and the effective amplitude of gravitational
waves from the HMNS is 4--$6 \times 10^{-22}$ at $f=2.1$--2.5~kHz for a
source distance of 100~Mpc. We also present the neutrino luminosity curve
when a black hole is formed for the first time. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-05 |
Ken'ichi |
Saikawa |
Institute for Cosmic Ray Research The University of Tokyo |
Gravitational waves from cosmic string-domain wall networks |
| Abstract |
The networks of domain walls bounded by cosmic strings naturally arise
in the theory of complex scalar field with a potential which has multiple
degenerate minima. In particular; QCD axion models predict the formation
of such string-wall networks in the early universe. Based on 3D lattice
simulations; we investigate the radiation of axion particles and gravitational
waves from these defect networks; and discuss its implications for axion
cosmology. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-06 |
Maresuke |
Shiraishi |
Nagoya University |
Violation of the Rotational Invariance in the CMB Bispectrum |
| Abstract |
We investigate a statistical anisotropy on the Cosmic Microwave Background
(CMB) bispectrum which can be generated from the primordial non-Gaussianity
induced by quantum fluctuations of a vector field. We find a new configurations
in the multipole space of the CMB bispectrum given by $\ell_1 = \ell_2
+ \ell_3 + 2; |\ell_2 - \ell_3| - 2$ and their permutations; which violate
the rotational invariance; such as an off-diagonal configuration in the
CMB power spectrum. We also find that in a model presented by Yokoyama
and Soda (2008); the amplitude of the statistically anisotropic bispectrum
in the above configurations becomes as large as that in other configuration
such as $\ell_1 = \ell_2 + \ell_3$. As a result; it might be possible to
detect these contributions in the future experiments and then it would
give us novel information about the physics of the early Universe. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-07 |
Daisuke |
Yamauchi |
Institute for Cosmic Ray Research |
Weak lensing of CMB from cosmic (super-)strings |
| Abstract |
We present calculations of cosmic (super-)strings contribution to cosmic
microwave background anisotropy and polarization spectrum due to gravitational
weak lensing. We develop a method to calculate angular power spectrum of
convergence due to cosmic (super-)string network. We clarify the dependence
of the CMB polarization due to weak lensing on the intercommuting probability
explicitly. We find that the the contributions from segments located at
low redshift are not negligible and lensing events from low mutipole modes
of lensing potential are essential even at high multipole in CMB. As the
intercommuting probability decreases; the spectra of the convergence; the
lensed temperature; and polarization increase because the number density
of string segment becomes larger. An important feature for observing CMB
polarizations is that the small scale lensed spectra due to cosmic (super-)string
network could decay slowly; compared with primordial scalar perturbations. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-08 |
Satoshi |
Maeda |
Department of physics Kyoto University |
Generation of the primordial magnetic fields from the non-adiabatic fluctuations
at the pre-recombination era |
| Abstract |
Many mechanisms in the generation of the primordial magnetic fields are
proposed. One of them is the generation from the Thomson scattering at
the pre-recombination era. In past works; the adiabatic fluctuations were
only considered. Then it is shown analytically that the generation appears
from the second-order tight coupling approximation for the Thomson scattering.
However; if the isocurvature fluctuation of baryons; i.e. the non-adiabatic
fluctuation exists; the fields arise at the first order. We evaluate the
power spectrum of the magnetic fields generated by the non-adiabatic fluctuations
of baryons. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-09 |
Kouji |
Nakamura |
National Astronomical Observatory of Japan |
Construction of gauge-invariant variables of linear metric perturbation
on general background spacetime |
| Abstract |
It is shown that the linear order metric perturbation is decomposed into
gauge-invariant and gauge-variant parts on the general background spacetime
which admits ADM decomposition. We explicitly construct the gauge-invariant
and gauge-variant parts of the linear metric perturbations through the
assumption of the existence of some Green functions. We also confirm the
result through another approach. This implies that we can develop the higher-order
gauge-invariant perturbation theory on generic background spacetime. Remaining
issues to complete the general-framework of the higher-order gauge-invariant
perturbation theories are also discussed. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-10 |
Masaru |
Adachi |
Hiroisaki University |
No Dark Energy is required if we accept a slightly inhomogeneous viewpoint |
| Abstract |
We re-analyze the magnitude-redshift relation of the observed type Ia supernovae
and examine an alternative possibility without Dark Energy. We find that
no Dark Energy is required if we accept the following slightly inhomogeneous
universe: 1) the expansion rate in the nearby $( z\lesssim0.1 )$ region
is slightly $( \sim 10 \% )$ faster than that in the distant $( z>0.1
)$ region. 2) the clumpiness parameter $\alpha$ in the Dyer \& Roeder
distance is also slightly inhomogeneous; $\alpha \sim 0$ in the nearby
region while $\alpha \sim 0.2$ in the distant region. We will also investigate
a simple; inhomogeneous model which satisfies the above required following
1) and 2). |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-11 |
Li-Ming |
Cao |
Department of Physics Kinki University Osaka Japan |
Deformation of Codimension-2 surfaces and Horizon thermodynamics |
| Abstract |
The deformation equation of a spacelike submanifold with an arbitrary codimension
is given by a general construction without using local frames. We show
how the thermodynamics of trapping horizons is related to these deformation
equations in two different formalisms: with and without introducing quasilocal
energy. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-12 |
Shunichiro |
Kinoshita |
Department of Physics Kyoto University |
Hawking temperature for near-equilibrium black holes |
| Abstract |
We discuss Hawking temperature for non-stationary black holes by semi-classical
analysis. We evaluate the Bogoliubov coefficients using the saddle point
approximation. When a spacetime slowly evolves such as a black hole which
varies the mass; we show that the temperature observed at asymptotic observers
is determined by a surface gravity of the past horizon. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-13 |
Hiromi |
Saida |
Daido University |
Universal Property of Quantum Gravity implied Uniqueness Theorem of Bekenstein-Hawking
Entropy |
| Abstract |
Contents are made of three steps. 1st: I show the uniqueness theorem of
Bekenstein-Hawking entropy. Proof is constructed in the framework of axiomatic
thermodynamics, without using any existing model of quantum gravity. 2nd:
I clarify the intrinsic property of Hilbert space of ordinary quantum mechanics
which justifies the Boltzmann formula so as to give "unique"
entropy. This property is the central basis for the consistency of quantum
statistical mechanics with ordinary thermodynamics. 3rd: Combine the above
steps. Suppose that BH entropy, which is unique as shown in step 1, is
given by the Boltzmann formula. This implies that the property of quantum
mechanics shown in step 2 is shared by the underlying quantum gravity.
From this, we find the suggestion that the potential of quantum gravitational
interaction, at short length scale such as Planck scale, is bounded below.
Furthermore, under some physical requirement, the gravity at Planck length
becomes repulsive, in order to let the thermal equilibrium of black hole
can exist under a suitable setting. This suggestion on underlying quantum
gravity is universal in the sense that no existing model of quantum gravity
is used in all the above discussions. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-14 |
Mitsuhiro |
Matsumoto |
Sokendai |
Time Evolution of Evaporating Black Rings |
| Abstract |
A black ring is in balance of self-gravitational and centrifugal forces.
We considered the decrease of mass and angular momentum via Hawking radiation
and investigated quasi-stationary time evolution of large radius black
rings. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-15 |
Masahiro |
Hotta |
Tohoku Unviersity |
Quantum Energy Teleportation and Black Hole |
| Abstract |
Recently a new protocol of quantum teleportation has been proposed which
attains effective energy transportation by local operations and classical
communication without breaking local energy conservation. In this presentation;
the application to black-hole physics is discussed. An introductory review
of the teleportation is available on the web site: http://www.tuhep.phys.tohoku.ac.jp/~hotta/
|
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O28-16 |
Shinya |
Tomizawa |
KEK |
New solution generation utilizing SL(2;R)-duality and new black holes |
| Abstract |
The dimensional reduction of (the bosonic sector of) five-dimensional minimal
supergravity to four dimensions leads to a theory with a massless axion
and a dilaton coupled to gravity and two U(1) gauge fields (one of which
has Chern-Simons coupling); whose field equations have SL(2;R) invariance.
Utilizing this SL(2;R)-duality; we provide a new formalism for solution
generation. As an example; applying it to the Rasheed solutions; which
are known to describe dyonic rotating black holes (from the four-dimensional
point of view) of five-dimensional pure gravity; we obtain rotating Kaluza-Klein
black hole solutions in five-dimensional minimal supergravity. We also
show that the solutions have six charges: mass; angular momentum; Kaluza-Klein
electric/magnetic charges and electric/magnetic charges of the Maxwell
field; four of which are related by a constraint. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| I29-01 |
Marco |
Peloso |
University of Minnesota |
Phenomenology of a pseudoscalar inflaton: naturally large nongaussianity |
| Abstract |
|
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O29-01 |
Kazuyuki |
Sugimura |
Yukawa institute for theoretical physics Kyoto university |
Multi-field open inflation and instanton |
| Abstract |
In a multi-field open inflation model; the inflaton starts slow-rolling
after tunneling of another field. In previous studies; they assumed that
the inflaton field does not affect the tunneling. It was not known whether
multi-field instanton with gravity exists when we consider the interaction
between the inflaton and the tunneling field. We find that there exists
a solution for multi-field instanton. We use this solution to describe
tunneling in multi-field open inflation; and solve the evolution of the
universe after tunneling to make sure that slow-roll inflation lasts more
than 60 e-foldings. We find a solution which realizes the multi-field open
inflation scenario. We also investigate the effect of the interaction on
false vacuum decay rate. Decay rate tends to increase when the effect of
the interaction is taken into consideration. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O29-02 |
Tsutomu |
Kobayashi |
Hakubi Center Kyoto University |
Generalized G-inflation |
| Abstract |
We study generalized Galileons as a framework to develop the most general
single-field inflation models ever; Generalized G-inflation; containing
yet further generalization of G-inflation; as well as previous examples
such as k-inflation; extended inflation; and new Higgs inflation as special
cases. We investigate the background and perturbation evolution in this
model; calculating the most general quadratic actions for tensor and scalar
cosmological perturbations to give the stability criteria and the power
spectra of primordial fluctuations. It is pointed out that the Horndeski
theory and the generalized Galileons are equivalent. In particular; even
the non-minimal coupling to the Gauss-Bonnet term is included in the generalized
Galileons in a non-trivial manner. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O29-03 |
Fuminiobu |
Takahashi |
Tohoku University |
Non-Gaussianity from Hilltop Curvaton |
| Abstract |
Focusing on the case that the curvaton is a pseudo-Nambu-Goldstone (NG)
boson of a broken U(1) symmetry; we show that the resulting density perturbations
are strongly enhanced towards the hilltop region of the energy potential;
accompanied by a mild increase of the non-Gaussianity. Such hilltop NG-curvatons
can produce observationally suggested density perturbations under wide
ranges of inflation/reheating scales; and further predict the non-Gaussianity
of the density perturbations to lie within the range 10< fNL <30. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O29-04 |
Atsushi |
Naruko |
Yukawa Institute for Theoretical Physics Kyoto University |
Beyond delta N formalism |
| Abstract |
We develop a theory of nonlinear cosmological perturbations on superhorizon
scales for a multi-component scalar field with a general kinetic term and
a general form of the potential in the context of inflationary cosmology.
We employ the ADM formalism and the spatial gradient expansion approach;
characterised by O(\epsilon^2); where \epsilon = 1/(HL) is a small parameter
representing the ratio of the Hubble radius to the characteristic length
scale L of perturbations. We provide a formalism to obtain the solution
in the multi field case; assuming a complete set of background solution
of scalar fields. This formalism can be applied to the calculation of the
superhorizon evolution of a primordial curvature perturbations beyond the
so-called delta N formalism; equivalent to O(\epsilon^0). As a specific
example; we consider canonical scalar fields and a type of separable potential
and discuss the effects of these O(\epsilon^2) correction in curvature
perturbations. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O29-05 |
Yuichi |
Takamizu |
Waseda University |
Gradient expansion approach to multi-field inflation |
| Abstract |
We develop a theory of nonlinear cosmological perturbations on superhorizon
scales for a multi-component scalar field with a general kinetic term and
a general form of the potential in the context of inflationary cosmology.
We employ the ADM formalism and the spatial gradient expansion approach;
characterised by a small parameter representing the ratio of the Hubble
radius to the characteristic length scale of perturbations. We provide
a formalism to obtain the solution in the multi field case; if we know
a complete set of solution of scalar fields. This formalism can be applied
to the calculation of the superhorizon evolution of a primordial non-Gaussianity
beyond the so-called $\delta N$ formalism; equivalent to the leading order
in the gradient expansion. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O29-06 |
Masato |
Nozawa |
Theory Center IPNS KEK |
Parity violation in graviton non-Gaussianity |
| Abstract |
We study parity violation in graviton non-gaussianity generated during
inflation. We develop a useful formalism to calculate graviton non-gaussianity.
Using this formalism; we explicitly calculate the parity violating part
of the bispectrum for primordial gravitational waves in the exact de Sitter
spacetime and prove that no parity violation appears in the non-gaussianity.
We also extend the analysis to slow-roll inflation and find that the parity
violation of the bispectrum is proportional to the slow-roll parameter.
We argue that parity violating non-gaussianity can be tested by the CMB.
Our results are also useful for calculating three-point function of the
stress tensor in the non-conformal field theory through the gravity/field
theory correspondence. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O29-07 |
Margarita |
Khabibullina |
Kazan (Volga Region) Federal University |
The estimation of black-hole masses in distant radio galaxies |
| Abstract |
We have estimated the masses of the central supermassive black holes of
2442 radio galaxies froma catalog compiled using data from the NED; SDSS;
and CATS databases. Mass estimates based on optical photometry and radio
data are compared. Relationships between the mass of the central black
hole M {/p bh } and the redshift z p are constructed for both wavelength
ranges. Upperenvelope cubic regression fits are obtained using the maximum
estimates of the black-hole masses. The optical and radio upper envelopes
show similar behavior; and have very similar peaks in position; z p ≅
1.9; and amplitude; log M p/bh = 9.4. This is consistent with a model in
which the growth of the supermassive black holes is self-regulating; with
this redshift corresponding to the epoch when the accretion-flow phase
begins to end and the nuclear activity falls off. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O29-08 |
Yoshiaki |
Kato |
National Astronomical Observatory Japan |
Exploring the Growth History of Massive Black Holes by Measuring the Spin
of the Massive Black Hole Sagittarius A* |
| Abstract |
We report on our measurement of the spin of a supermassive black hole (SMBH)
in the Galactic center; Sagittarius A* (Sgr A*); by using disk seismology.
Recent radio observations of Sgr A* have discovered quasi-periodic oscillations
(QPOs) at several periods of 16.8; 22.2; 31.4; and 56.4 min; their ratios
roughly of 3:4:6:10 (Miyoshi et al. 2011). Some of them are consistent
with periods discovered in the near-infrared and x-ray bands. Such periodicity
having a ratio of small integers at multiple observing bands indicates
that the origin of QPOs is a global disk oscillation excited by the resonance
between geodesic modes of the disk. Actually; a ratio of 2:3 is a well-known
feature for the high-frequency QPOs in stellar-mass black holes within
the galactic x-ray binaries. We find a relation between geodesic modes
and the observed periods because the resonant disk oscillation model for
a given spin parameter agreed well with the observed QPOs within the error
of the estimated black hole mass. By using the relation; we find the spin
of black hole have a unique value of 0.44 which is smaller than the generally
accepted value for SMBH (Kato et al. 2010). We will give an overview of
disk seismology and also discuss on why SMBH have small spin by considering
mass accretion history of massive black holes. We anticipate that studies
of QPOs in other galaxies will open a new window to survey the growth history
of massive black holes. |
| Back |
| Talk ID |
First Name |
Last Name |
Affiliation |
Presentation Title |
| O29-09 |
Makoto |
Miyoshi |
National Astronomical Observatory Japan |
Oscillation Phenomena in the Disk around the Massive Black Hole Sagittarius
A¡ö |
| Abstract |
We report the detection of radio QPOs with structure changes using the
Very Long Baseline Array (VLBA) at 43GHz. We found conspicuous patterned
changes of the structure with P = 16.8; 22.2; 31.4; 56.4 min roughly in
a 3:4:6:10 ratio. The first two periods show a rotating one-arm structure;
while the P = 31.4 min shows a rotating 3-arm structure; as if viewed edge-on.
At the central 50micro-asec the P = 56.4 min period shows a double amplitude
variation of those in its surroundings. Spatial distributions of the oscillation
periods suggest that the disk of SgrA* is roughly edge-on; rotating around
an axis with PA = -10degree. Presumably; the observed VLBI images of SgrA
at 43 GHz retain several features of the black hole accretion disk of SgrA*
in spite of being obscured and broadened by scattering of surrounding plasma. |
| Back |