Floating Black Hole in the Karch-Randall Model and its Holographic Dual (2009)
Tanahashi, Norihiro, Tanaka, Takahiro
To investigate the holography in the Karch-Randall (KR) braneworld model, we construct time-symmetric initial data of black holes floating in the bulk, and compare it with its holographic dual, which...
Quantum Back Reaction to asymptotically AdS Black Holes (2009)
Kashiyama, Kazumi, Tanahashi, Norihiro, Flachi, Antonino, Tanaka, Takahiro
We analyze the effects of the back reaction due to a conformal field theory (CFT) on a black hole spacetime with negative cosmological constant. We study the geometry numerically obtained by taking...
DECIGO/BBO as a probe to constrain alternative theories of gravity (2009)
We calculate how strongly one can constrain the alternative theories of gravity with deci-Hz gravitational wave interferometers such as DECIGO and BBO. Here we discuss Brans-Dicke theory and massive...
We calculate how strong one can put constraints on the alternative theories of gravities such as Brans-Dicke and massive graviton theories with LISA. We consider the inspiral gravitational waves from...
Casimir Effect on the brane (2009)
Flachi, Antonino, Tanaka, Takahiro
We consider the Casimir effect between two parallel plates localized on a brane. We argue that in order to properly compute the contribution to the Casimir energy due to any higher dimensional field,...
Lorentz boost and non-Gaussianity in multi-field DBI-inflation (2009)
Mizuno, Shuntaro, Arroja, Frederico, Koyama, Kazuya, Tanaka, Takahiro
We show that higher-order actions for cosmological perturbations in the multi-field DBI-inflation model are obtained by a Lorentz boost from the rest frame of the brane to the frame where the brane...
On the full trispectrum in single field DBI-inflation (2009)
Arroja, Frederico, Mizuno, Shuntaro, Koyama, Kazuya, Tanaka, Takahiro
We compute the tree-level connected four-point function of the primordial curvature perturbation for a fairly general minimally coupled single field inflationary model, where the inflaton's...
Ando, Masaki, Kawamura, Seiji, Sato, Shuichi, Nakamura, Takashi, Tsubono, Kimio, Araya, Akito, ...
DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory), which is a future space gravitational wave antenna. DECIGO is expected...
Influence on observation from IR divergence during inflation -- Multi field inflation -- (2009)
Urakawa, Yuko, Tanaka, Takahiro
We propose one way to regularize the fluctuations generated during inflation, whose infrared (IR) corrections diverge logarithmically. In the case of a single field inflation model, recently, we...
Influence on observation from IR divergence during inflation -- Single field inflation -- (2009)
Urakawa, Yuko, Tanaka, Takahiro
A naive computation of the correlation functions of fluctuations generated during inflation suffers from logarithmic divergences in the infrared (IR) limit. In this paper, we propose one way to solve...
Particle production in models with helicity-0 graviton ghost in de Sitter spacetime (2008)
Izumi, Keisuke, Tanaka, Takahiro
We revisit the problem of the helicity-0 ghost mode of massive graviton in the de Sitter background. In general, the presence of a ghost particle, which has negative energy, drives the vacuum to be...
Yokoyama, Shuichiro, Suyama, Teruaki, Tanaka, Takahiro
We present a new efficient method for computing the non-linearity parameters of the higher order correlation functions of local type curvature perturbations in inflation models having a $\cal...
Spin Polarization Effects in Micro Black Hole Evaporation (2008)
Flachi, Antonino, Sasaki, Misao, Tanaka, Takahiro
We consider the evaporation of rotating micro black holes produced in highly energetic particle collisions, taking into account the polarization due to the coupling between the spin of the emitted...
Ando, Masaki, Kawamura, Seiji, Nakamura, Takashi, Tsubono, Kimio, Tanaka, Takahiro, Funaki, Ikkoh, ...
DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) which is a future space gravitational wave antenna. DECIGO is expected...
The Japanese space gravitational wave antenna; DECIGO (2008)
Kawamura, Seiji, Ando, Masaki, Nakamura, Takashi, Tsubono, Kimio, Tanaka, Takahiro, Funaki, Ikkoh, ...
DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational wave antenna. DECIGO is expected to open a new window of observation for gravitational...
Primordial perturbations and non-Gaussianities in DBI and general multi-field inflation (2008)
Langlois, David, Renaux-Petel, Sebastien, Steer, Daniele A, Tanaka, Takahiro
We study cosmological perturbations in general inflation models with multiple scalar fields and arbitrary kinetic terms, with special emphasis on the multi-field extension of Dirac-Born-Infeld (DBI)...
Primordial perturbations and non-Gaussianities in DBI and general multi-field inflation (2008)
Langlois, David, Renaux-Petel, Sebastien, Steer, Daniele A., Tanaka, Takahiro
We study cosmological perturbations in general inflation models with multiple scalar fields and arbitrary kinetic terms, with special emphasis on the multi-field extension of Dirac-Born-Infeld (DBI)...
Primordial Fluctuations and Non-Gaussianities in Multifield Dirac-Born-Infeld Inflation (2008)
Langlois, David, Renaux-Petel, Sebastien, Steer, Daniele A, Tanaka, Takahiro
We study Dirac-Born-Infeld (DBI) inflation models with multiple scalar fields. We show that the adiabatic and entropy modes propagate with a common effective sound speed and are thus amplified at the...
Primordial fluctuations and non-Gaussianities in multi-field DBI inflation (2008)
Langlois, David, Renaux-Petel, Sebastien, Steer, Daniele A., Tanaka, Takahiro
We study Dirac-Born-Infeld (DBI) inflation models with multiple scalar fields. We show that the adiabatic and entropy modes propagate with a common effective sound speed and are thus amplified at the...
Online Support System for Mediator Education (2008)
Takahiro Tanaka, Yoshiaki Yasumura, Daisuke Katagami, Katsumi Nitta
Resolution) has been becoming popular instead of the trial. However, to educate the mediation skill, much training is needed. In this paper, we introduce the overview of the online mediator education...
Vacuum polarization in asymptotically anti-de Sitter black hole geometries (2008)
Flachi, Antonino, Tanaka, Takahiro
We study the polarization of the vacuum for a scalar field, $$, on an asymptotically anti-de Sitter black hole geometry. The method we follow uses the WKB analytic expansion and point-splitting...
Time-symmetric initial data of large brane-localized black hole in RS-II model (2007)
Tanahashi, Norihiro, Tanaka, Takahiro
In the aim of shedding a new light on the classical black hole evaporation conjecture stating that a static brane-localized black hole (BH) larger than the bulk curvature scale does not exist in...
Primordial Non-Gaussianity in Multi-Scalar Inflation (2007)
Yokoyama, Shuichiro, Suyama, Teruaki, Tanaka, Takahiro
We give a concise formula for the non-Gaussianity of the primordial curvature perturbation generated on super-horizon scales in multi-scalar inflation model without assuming slow-roll conditions....
Implication of Classical Black Hole Evaporation Conjecture to Floating Black Holes (2007)
In Randall-Sundrum single-brane (RS-II) model, it was conjectured that there is no static large black hole localized on the brane based on adS/CFT correspondence. Here we consider the phase diagram...
No de Sitter invariant vacuum in massive gravity theory with ghost (2007)
Izumi, Keisuke, Tanaka, Takahiro
In this letter we point out that the massive gravity theory with a graviton ghost mode in de Sitter background cannot possess a de Sitter invariant vacuum state. In order to avoid a negative norm...
Bubbles in the Self-Accelerating Universe (2007)
Izumi, Keisuke, Koyama, Kazuya, Pujolas, Oriol, Tanaka, Takahiro
We revisit the issue of the stability in the Dvali-Gabadadze-Porrati model, by considering the nucleation of bubbles of the conventional branch within the self-accelerating branch. We construct an...
Can infrared gravitons screen $\Lambda$? (2007)
Garriga, Jaume, Tanaka, Takahiro
It has been suggested that infrared gravitons in de Sitter space may lead to a secular screening of the effective cosmological constant. This seems to clash with the naive expectation that the...
Primordial Non-Gaussianity in Multi-Scalar Slow-Roll Inflation (2007)
Yokoyama, Shuichiro, Suyama, Teruaki, Tanaka, Takahiro
We analyze the non-Gaussianity for primordial curvature perturbations generated in multi-scalar slow-roll inflation model including the model with non-separable potential by making use of $\delta N$...
Branes and Black holes in Collision (2007)
Flachi, Antonino, Tanaka, Takahiro
We study the collision of a brane with a black hole. Our aim is to explore the topology changing process of perforation of a brane. The brane is described as a field theoretical domain wall in the...
Ganz, Katsuhiko, Hikida, Wataru, Nakano, Hiroyuki, Sago, Norichika, Tanaka, Takahiro
General orbits of a particle of small mass $\mu$ around a Kerr black hole of mass $M$ are characterized by three parameters: the energy, the angular momentum and the Carter constant. The...
Unexorcized ghost in DGP brane world (2006)
Izumi, Keisuke, Koyama, Kazuya, Tanaka, Takahiro
The braneworld model of Dvali-Gabadadze-Porrati realizes the self-accelerating universe. However, it is known that this cosmological solution contains a spin-2 ghost. We study the possibility of...
Wronskian Formulation of the Spectrum of Curvature Perturbations (2006)
Yokoyama, Shuichiro, Tanaka, Takahiro, Sasaki, Misao, Stewart, Ewan D.
We present a new formulation for the evaluation of the primordial spectrum of curvature perturbations generated during inflation, using the fact that the Wronskian of the scalar field perturbation...
Critical escape velocity of black holes from branes (2006)
Flachi, Antonino, Pujolas, Oriol, Sasaki, Misao, Tanaka, Takahiro
In recent work we have shown that a black hole stacked on a brane escapes once it acquires a recoil velocity. This result was obtained in the {\it probe-brane} approximation, {\it i.e.}, when the...
Dynamics of domain walls intersecting black holes (2006)
Flachi, Antonino, Pujolas, Oriol, Sasaki, Misao, Tanaka, Takahiro
Previous studies concerning the interaction of branes and black holes suggested that a small black hole intersecting a brane may escape via a mechanism of reconnection. Here we consider this problem...
Black hole production in tachyonic preheating (2006)
Suyama, Teruaki, Tanaka, Takahiro, Bassett, Bruce, Kudoh, Hideaki
We present fully non-linear simulations of a self-interacting scalar field in the early universe undergoing tachyonic preheating. We find that density perturbations on sub-horizon scales which are...
Exact Wave Propagation in a Spacetime with a Cosmic String (2005)
Suyama, Teruaki, Tanaka, Takahiro, Takahashi, Ryuichi
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...
The adiabatic evolution of orbital parameters in the Kerr spacetime (2005)
Sago, Norichika, Tanaka, Takahiro, Hikida, Wataru, Ganz, Katsuhiko, Nakano, Hiroyuki
We investigate the adiabatic orbital evolution of a point particle in the Kerr spacetime due to the emission of gravitational waves. In the case that the timescale of the orbital evolution is enough...
The spectrum of gravitational waves in Randall-Sundrum braneworld cosmology (2005)
Kobayashi, Tsutomu, Tanaka, Takahiro
We study the generation and evolution of gravitational waves (tensor perturbations) in the context of Randall-Sundrum braneworld cosmology. We assume that the initial and final stages of the...
Gravitational radiation reaction (2005)
We give a short personally-biased review on the recent progress in our understanding of gravitational radiation reaction acting on a point particle orbiting a black hole. The main motivation of this...
Adiabatic radiation reaction to the orbits in Kerr Spacetime (2005)
Sago, Norichika, Tanaka, Takahiro, Hikida, Wataru, Nakano, Hiroyuki
Geodesic motion of a point particle in Kerr geometry has three constants of motion, energy $E$, azimuthal angular momentum $L$, and Carter constant $Q$. Under the adiabatic approximation, radiation...
Escape of black holes from the brane (2005)
Flachi, Antonino, Tanaka, Takahiro
TeV-scale gravity theories allow the possibility of producing small black holes at energies that soon will be explored at the LHC or at the Auger observatory. One of the expected signatures is the...
A New delta N Formalism for Multi-Component Inflation (2005)
Lee, Hyun-Chul, Sasaki, Misao, Stewart, Ewan D., Tanaka, Takahiro, Yokoyama, Shuichiro
The delta N formula that relates the final curvature perturbation on comoving slices to the inflaton perturbation on flat slices after horizon crossing is a powerful and intuitive tool to compute the...
Quantum-mechanical generation of gravitational waves in braneworld (2005)
Kobayashi, Tsutomu, Tanaka, Takahiro
We study the quantum-mechanical generation of gravitational waves during inflation on a brane embedded in a five-dimensional anti-de Sitter bulk. To make the problem well-posed, we consider the setup...
Kobayashi, Tsutomu, Tanaka, Takahiro
Tensor perturbations in an expanding braneworld of the Randall Sundrum type are investigated. We consider a model composed of a slow-roll inflation phase and the succeeding radiation phase. The...
Five-dimensional black strings in Einstein-Gauss-Bonnet gravity (2004)
Kobayashi, Tsutomu, Tanaka, Takahiro
We consider black-string-type solutions in five-dimensional Einstein-Gauss-Bonnet gravity. Numerically constructed solutions under static, axially symmetric and translationally invariant metric...
Hikida, Wataru, Jhingan, Sanjay, Nakano, Hiroyuki, Sago, Norichika, Sasaki, Misao, Tanaka, Takahiro
In a previous paper, based on the black hole perturbation approach, we formulated a new analytical method for regularizing the self-force acting on a particle of small mass $\mu$ orbiting a...
Are black holes over-produced during preheating? (2004)
Suyama, Teruaki, Tanaka, Takahiro, Bassett, Bruce, Kudoh, Hideaki
We provide a simple but robust argument that primordial black hole (PBH) production generically does {\em not} exceed astrophysical bounds during the resonant preheating phase after inflation. This...
Leading order corrections to the cosmological evolution of tensor perturbations in braneworld (2004)
Kobayashi, Tsutomu, Tanaka, Takahiro
Tensor type perturbations in the expanding brane world of the Randall Sundrum type are investigated. We consider a model composed of slow-roll inflation phase and the succeeding radiation phase. The...
Massless scalar fields and infrared divergences in the inflationary brane world (2004)
Pujolas, Oriol, Tanaka, Takahiro
We study the quantum effects induced by bulk scalar fields in a model with a de Sitter (dS) brane in a flat bulk (the Vilenkin-Ipser-Sikivie model) in more than four dimensions. In ordinary dS space,...
AdS/CFT correspondence in a Friedmann-Lemaitre-Robertson-Walker brane (2004)
According to the AdS/CFT correspondence conjecture, the Randall-Sundrum infinite braneworld is equivalent to four dimensional Einstein gravity with ${\cal N}=4$ super Yang-Mills fields at low...
Bulk inflaton shadows of vacuum gravity (2003)
Kobayashi, Tsutomu, Tanaka, Takahiro
We introduce a $(5+m)$-dimensional vacuum description of five-dimensional bulk inflaton models with exponential potentials that makes analysis of cosmological perturbations simple and transparent. We...
Hikida, Wataru, Jhingan, Sanjay, Nakano, Hiroyuki, Sago, Norichika, Sasaki, Misao, Tanaka, Takahiro
We formulate a new analytical method for regularizing the self-force acting on a particle of small mass $\mu$ orbiting a black hole of mass $M$, where $\mu\ll M$. At first order in $\mu$, the...
Weak gravity in DGP braneworld model (2003)
We analyze the weak gravity in the braneworld model proposed by Dvali-Gabadadze-Porrati, in which the unperturbed background spacetime is given by five dimensional Minkowski bulk with a brane which...
Primordial gravitational waves in inflationary braneworld (2003)
Kobayashi, Tsutomu, Kudoh, Hideaki, Tanaka, Takahiro
We study primordial gravitational waves from inflation in Randall-Sundrum braneworld model. The effect of small change of the Hubble parameter during inflation is investigated using a toy model given...
Inoue, Kaiki Taro, Tanaka, Takahiro
In many braneworld models, gravity is largely modified at the electro-weak scale ~ 1TeV. In such models, primordial black holes (PBHs) with lunar mass M ~ 10^{-7}M_sun might have been produced when...
Application of the Separate Universe Approach to Preheating (2003)
Tanaka, Takahiro, Bassett, Bruce
The dynamics of preheating after inflation has not been clearly understood yet.In particular, the issue of the generation of metric perturbations during preheating on super-horizon scale is still...
Moduli stabilization in higher dimensional brane models (2003)
Flachi, Antonino, Garriga, Jaume, Pujolas, Oriol, Tanaka, Takahiro
We consider a class of warped higher dimensional brane models with topology $M \times \Sigma \times S^1/Z_2$, where $\Sigma$ is a $D_2$ dimensional manifold. Two branes of codimension one are...
Small localized black holes in a braneworld: Formulation and numerical method (2003)
Kudoh, Hideaki, Tanaka, Takahiro, Nakamura, Takashi
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...
Generation of dark radiation in the bulk inflaton model (2003)
Tanaka, Takahiro, Himemoto, Yoshiaki
We investigate the dynamics of a bulk scalar field with various decay channels in the Randall-Sundrum infinite braneworld scenario. A bulk scalar field in this scenario has a quasi-localized mode...
Braneworld reheating in the bulk inflaton model (2002)
Himemoto, Yoshiaki, Tanaka, Takahiro
In the context of the braneworld inflation driven by a bulk scalar field, we study the energy dissipation from the bulk scalar field into the matter on the brane in order to understand the reheating...
Improvement on the metric reconstruction scheme in the Regge-Wheeler-Zerilli formalism (2002)
Jhingan, Sanjay, Tanaka, Takahiro
We study master variables in the Regge-Wheeler-Zerilli formalism. We show that a specific choice of new variables is suitable for studying perturbation theory from the viewpoint of radiation reaction...
Can a brane fluctuate freely? (2002)
Ishibashi, Akihiro, Tanaka, Takahiro
No, it cannot in the following sense if a self-gravitating vacuum brane is concerned. Once we write down the full set of linear perturbation equations of the system containing a self-gravitating...
Brane collisions and braneworld cosmology (2002)
Gen, Uchida, Ishibashi, Akihiro, Tanaka, Takahiro
Recently, we proposed a new braneworld model [GIT] in which the collision of a brane universe and a vacuum bubble coming from the extra-dimension is utilized as a trigger of brane big-bang. In this...
Kudoh, Hideaki, Tanaka, Takahiro
We discuss gravitational perturbations in the Randall-Sundrum two branes model with radius stabilization. Following the idea by Goldberger and Wise for the radius stabilization, we introduce a scalar...
Classical black hole evaporation in Randall-Sundrum infinite braneworld (2002)
After the gravity induced on the brane in the Randall-Sundrum (RS) infinite braneworld is briefly reviewed, we discuss the possibility that black holes evaporate as a result of classical evolution in...
Bulk scalar field in the braneworld can mimic the 4D inflaton dynamics (2001)
Himemoto, Yoshiaki, Tanaka, Takahiro, Sasaki, Misao
Based on the recently proposed scenario of inflation driven by a bulk scalar field in the braneworld of the Randall-Sundrum (RS) type, we investigate the dynamics of a bulk scalar field on the...
Cosmological perturbations in the 5D Big Bang (2001)
Garriga, Jaume, Tanaka, Takahiro
Bucher [Bucher2001] has recently proposed an interesting brane-world cosmological scenario where the ``Big Bang'' hypersurface is the locus of collision of two vacuum bubbles which nucleate in a five...
Second order perturbations in the radius stabilized Randall-Sundrum two branes model (2001)
Kudoh, Hideaki, Tanaka, Takahiro
The nonlinear gravitational interaction is investigated in the Randall-Sundrum two branes model with the radius stabilization mechanism. As the stabilization model, we assume a single scalar field...
Moduli effective action in warped brane world compactifications (2001)
Garriga, Jaume, Pujolas, Oriol, Tanaka, Takahiro
We consider a class of 5-D brane-world solutions with a power-law warp factor $a(y)\propto y^{q}$, and bulk dilaton with profile $\phi \propto \ln y$, where $y$ is the proper distance in the extra...
Brane Big-Bang Brought by Bulk Bubble (2001)
Gen, Uchida, Ishibashi, Akihiro, Tanaka, Takahiro
We propose an alternative inflationary universe scenario in the context of Randall-Sundrum braneworld cosmology. In this new scenario the existence of extra-dimension(s) plays an essential role....
Second Order Perturbations in the Randall-Sundrum Infinite Brane-World Model (2001)
Kudoh, Hideaki, Tanaka, Takahiro
We discuss the non-linear gravitational interactions in the Randall-Sundrum single brane model. If we naively write down the 4-dimensional effective action integrating over the fifth dimension with...
A comment on trans-Planckian physics in inflationary universe (2000)
There are several works searching for a clue of trans-Planckian physics on the primordial density perturbation spectrum. Here we would like to point out an important aspect which has been overlooked...
The First Search for Gravitational Waves from Inspiraling Compact Binaries using TAMA300 data (2000)
Tagoshi, Hideyuki, Kanda, Nobuyuki, Tanaka, Takahiro, Tatsumi, Daisuke, Telada, Souichi
We analyzed 6 hours of data from the TAMA300 detector by matched filtering, searching for gravitational waves from inspiraling compact binaries. We incorporated a two-step hierarchical search...
Analytic derivation of the map of null rays passing near a naked singularity (2000)
Tanaka, Takahiro, Singh, T. P.
Recently the energy emission from a naked singularity forming in spherical dust collapse has been investigated. This radiation is due to the particle creation in a curved spacetime. In this...
Naked singularities and quantum gravity (2000)
Harada, Tomohiro, Iguchi, Hideo, Nakao, Ken-ichi, Singh, T. P., Tanaka, Takahiro, Vaz, Cenalo
There are known models of spherical gravitational collapse in which the collapse ends in a naked shell-focusing singularity for some initial data. If a massless scalar field is quantized on the...
Asymptotic Behavior of Perturbations in Randall-Sundrum Brane-World (2000)
The asymptotic behavior of metric perturbations in Randall-Sundrum infinite brane world is carefully investigated. Perturbations generated by matter fields on the brane are shown to be regular even...
Radion effective potential in the Brane-World (2000)
Garriga, Jaume, Pujolas, Oriol, Tanaka, Takahiro
We show that in brane-world scenarios with warped extra dimensions, the Casimir force due to bulk matter fields may be sufficient to stabilize the radion field $\phi$. In particular, we calculate one...
Tanaka, Takahiro, Tagoshi, Hideyuki
We discuss a method to analyze data from interferometric gravitational wave detectors focusing on the technique of hierarchical search to detect gravitational waves from inspiraling binaries. For...
Gravity in the brane-world for two-branes model with stabilized modulus (2000)
Tanaka, Takahiro, Montes, Xavier
We present a complete scheme to discuss linear perturbations in the two-branes model of the Randall and Sundrum scenario with the stabilization mechanism proposed by Goldberger and Wise. We confirm...
On cosmological perturbations in FRW model with scalar field and false vacuum decay (2000)
Khvedelidze, Arsen, Lavrelashvili, George, Tanaka, Takahiro
The unconstrained reduced action corresponding to the dynamics of scalar fluctuations about the Friedmann-Robertson-Walker (FRW) background is derived using Dirac's method of description of singular...
Gravity in the Randall-Sundrum Brane World (1999)
Garriga, Jaume, Tanaka, Takahiro
We discuss the weak gravitational field created by isolated matter sources in the Randall-Sundrum brane-world. In the case of two branes of opposite tension, linearized Brans-Dicke (BD) gravity is...
Himemoto, Yoshiaki, Tanaka, Takahiro
The Hawking radiation is one of the most interesting phenomena predicted by the theory of quantum field in curved space. The origin of Hawking radiation is closely related to the fact that a particle...
Ioka, Kunihito, Tanaka, Takahiro, Nakamura, Takashi
Under the assumption that the Milky Way's dark halo consists of primordial black hole MACHOs (PBHMACHOs), the mass density of the halo can be measured by the low frequency gravitational waves...
The No-Negative Mode Theorem in False Vacuum Decay with Gravity (1999)
The so-called negative mode problem in the path integral approach to the false vacuum decay with the effect of gravity has been an unsolved problem. Several years ago, we proposed a conjecture which...
Linde, Andrei, Sasaki, Misao, Tanaka, Takahiro
The possibility to have an infinite open inflationary universe inside a bubble of a finite size is one of the most interesting realizations extensively discussed in the literature. The original idea...
Spectrum of Cosmological Perturbations in the One-Bubble Open Universe (1998)
Garriga, Jaume, Montes, Xavier, Sasaki, Misao, Tanaka, Takahiro
The spectrum of cosmological perturbations in the context of the one-bubble open inflation model is discussed, taking into account fluctuations of the metric. We find that, quite generically,thin...
Mechanical Properties of Spinel-Silicon Carbide Whisker Composites. (1998)
Kondoh, Isao, Okayama, Hideto, Tanaka, Takahiro, Tamari, Nobuyuki, Kose, Saburoh
Hot-pressing at 1800 C under 30 MPa for 30 min was used to prepare spinel composite ceramics reinforced with 0-40 vol% beta-silicon carbide whiskers. The mechanical properties (bending strength,...
Mechanical Properties of Zirconia-Alumina Whisker Composite Ceramics. (1998)
Tamari, Nobuyuki, Tanaka, Takahiro, Kondoh, Isao, Kose, Saburoh, Gotoh, Kohji
Zirconia (3 mol% Y2O3) composite ceramics reinforced with 10, 20 and 40 vol% alpha-alumina whiskers were prepared by hot-pressing at 1500 C under 30 MPa for 30 min, and the mechanical properties were...
Sintering of Zircon-Silicon Carbide Whisker Composites and Their Mechanical Properties. (1998)
Kondoh, Isao, Tanaka, Takahiro, Tamari, Nobuyuki
Zircon composites reinforced with 20 vol% silicon carbide whiskers were prepared by hot-pressing. Three kinds of silicon carbide whiskers with different diameters were used as a reinforcement agent....
Mechanical Properties of Alumina-Mullite Whisker Composites. (1998)
Tamari, Nobuyuki, Kondoh, Isao, Tanaka, Takahiro, Katsuki, Hiroaki
Composite alumina ceramics with a mullite whisker content of up to 30 vol% were fabricated by hot-pressing at 1400-1600 C under 30MPa for 30 min. The bending strength, hardness, elastic modulus and...
Oxidation Behavior of Spinel/Silicon Carbide Whisker Composite Ceramics. (1998)
Kondoh, Isao, Tanaka, Takahiro, Tamari, Nobuyuki
Oxidation behavior of a spinel (Mg2Al4O8) composite containing 30 vol% SiC whisker has been studied at 1300 C in air. The weight gain curve obeyed the parabolic law up to the oxidation time of 120 h,...
Fabrication of SiC-SiC Whisker Composite by Repeated Infiltration of Polycarbosilane. (1998)
Tanaka, Takahiro, Tamari, Nobuyuki, Kondoh, Isao, Iwasa, Mikio
SiC-SiC whisker composite was fabricated by infiltration of polycarbosilane (PCS) as a precursor for matrix into the whisker preform followed by the pyrolysis process. The density was improved by...
Low frequency gravitational waves from black hole MACHO binaries (1998)
Ioka, Kunihito, Tanaka, Takahiro, Nakamura, Takashi
The intensity of low frequency gravitational waves from black hole MACHO binaries is studied. First we estimate the gravitational wave background produced by black hole MACHO binaries in the Milky...
No supercritical supercurvature mode conjecture in one-bubble open inflation (1998)
Tanaka, Takahiro, Sasaki, Misao
In the path integral approach to false vacuum decay with the effect of gravity, there is an unsolved problem, called the negative mode problem. We show that the appearance of a supercritical...
Ioka, Kunihito, Chiba, Takeshi, Tanaka, Takahiro, Nakamura, Takashi
We study black hole MACHO binary formation through three-body interactions in the early universe at $t\sim 10^{-5}$s. The probability distribution functions of the eccentricity and the semimajor axis...
The density parameter and the Anthropic Principle (1998)
Garriga, Jaume, Tanaka, Takahiro, Vilenkin, Alexander
In the context of open inflation, we calculate the probability distribution for the density parameter $\Omega$. A large class of two field models of open inflation do not lead to infinite open...
Super-Horizon Scale Dynamics of Multi-Scalar Inflation (1998)
Sasaki, Misao, Tanaka, Takahiro
We consider the dynamics of a multi-component scalar field on super-horizon scales in the context of inflationary cosmology. We present a method to solve the perturbation equations on super- horizon...
Gravitational Radiation Reaction (1997)
Mino, Yasushi, Sasaki, Misao, Tanaka, Takahiro
We consider the radiation reaction to the motion of a point-like particle of mass $m$ and specific spin $S$ traveling on a curved background. Assuming $S=O(Gm)$ and $Gm\ll L$ where $L$ is the length...
Black Hole Perturbation (1997)
Mino, Yasushi, Sasaki, Misao, Shibata, Masaru, Tagoshi, Hideyuki, Tanaka, Takahiro
We present analytic calculations of gravitational waves from a particle orbiting a black hole. We first review the Teukolsky formalism for dealing with the gravitational perturbation of a black hole....
Gravitational Waves from Coalescing Black Hole MACHO Binaries (1997)
Nakamura, Takashi, Sasaki, Misao, Tanaka, Takahiro, Thorne, Kip S.
If MACHOs are black holes of mass about 0.5 solar mass, they must have been formed in the early universe when the temperature was about 1 GeV. We estimate that in this case in our galaxy's halo out...
Canonical Quantization of Cosmological Perturbations in the One Bubble Open Universe (1997)
Garriga, Jaume, Montes, Xavier, Sasaki, Misao, Tanaka, Takahiro
Faddeev and Jackiw's method for constrained systems is used to derive a gauge invariant formulation of cosmological perturbations in the one bubble inflationary universe. For scalar perturbations in...
Gravitational Radiation Reaction to a Particle Motion II: Spinning Particle (1997)
Mino, Yasushi, Sasaki, Misao, Tanaka, Takahiro
We discuss the leading order correction to the equation of motion of a particle with spin on an arbitrary spacetime. A particle traveling in a curved spacetime is known to trace a geodesic of the...
Classical Nature of the Inflaton Field with Self-Interaction (1997)
Tanaka, Takahiro, Sakagami, Masa-aki
Taking into account the effect of self-interaction, the dynamics of the quantum fluctuations of the inflaton field with $\lambda\phi^4$ potential is studied in detail. We find that the self...
Wall fluctuation modes and tensor CMB anisotropy in open inflation models (1997)
Sasaki, Misao, Tanaka, Takahiro, Yakushige, Yoshihiro
We calculate the spectrum of large angle cosmic microwave background (CMB) anisotropies due to quantum fluctuations of the gravitational wave modes in one-bubble open inflation models. We find the...
The Spectrum of Gravitational Wave Perturbations in the One-Bubble Open Inflationary Universe (1997)
Tanaka, Takahiro, Sasaki, Misao
We give the initial spectrum of quantized gravitational waves in the context of the one-bubble open inflationary universe scenario. In determining the quantum state after the bubble nucleation we...
Quantized gravitational waves in the Milne universe (1996)
Tanaka, Takahiro, Sasaki, Misao
The quantization of gravitational waves in the Milne universe is discussed. The relation between positive frequency functions of the gravitational waves in the Milne universe and those in the...
Gravitational Radiation Reaction to a Particle Motion (1996)
Mino, Yasushi, Sasaki, Misao, Tanaka, Takahiro
In this paper, we discuss the leading order correction to the equation of motion of the particle, which presumably describes the effect of gravitational radiation reaction. We derive the equation of...
Can the Simplest Two-Field Model of Open Inflation Survive? (1996)
Sasaki, Misao, Tanaka, Takahiro
We investigate the quantum fluctuations of an inflaton field in a two-field model of one-bubble open inflation. One of the inflatons is assumed to be responsible for the first false vacuum stage of...
Quantum fluctuations and CMB anisotropies in one-bubble open inflation models (1996)
Yamammoto, Kazuhiro, Sasaki, Misao, Tanaka, Takahiro
We first develop a method to calculate a complete set of mode functions which describe the quantum fluctuations generated in one-bubble open inflation models. We consider two classes of models. One...
Tagoshi, Hideyuki, Shibata, Masaru, Tanaka, Takahiro, Sasaki, Misao
Extending a method developed by Sasaki in the Schwarzschild case and by Shibata, Sasaki, Tagoshi, and Tanaka in the Kerr case, we calculate the post-Newtonian expansion of the gravitational wave...
Gravitational waves from a spinning particle in circular orbits around a rotating black hole (1996)
Tanaka, Takahiro, Mino, Yasushi, Sasaki, Misao, Shibata, Masaru
Using the Teukolsky and Sasaki-Nakamura formalisms for the perterbations around a Kerr black hole, we calculate the energy flux of gravitational waves induced by a {\it spinning} particle of mass...
Self Excitation of the Tunneling Scalar Field in False Vacuum Decay (1995)
Hamazaki, Takashi, Sasaki, Misao, Tanaka, Takahiro, Yamamoto, Kazuhiro
A method to determine the quantum state of a scalar field after $O(4)$-symmetric bubble nucleation has been developed recently. The method has an advantage that it concisely gives us a clear picture...
Large Angle CMB Anisotropy in an Open Universe in the One-Bubble Inflationary Scenario (1995)
Yamamoto, Kazuhiro, Sasaki, Misao, Tanaka, Takahiro
We consider an alternative scenario of inflation which can account for a spatially open universe. It is similar to the old inflation in which the bubble nucleation occurs in the sea of false vacuum,...
Euclidian Vacuum Mode Functions for a Scalar Field on Open De Sitter Spacetime (1994)
Sasaki, Misao, Tanaka, Takahiro, Yamamoto, Kazuhiro
Motivated by recent studies of the one-bubble inflationary universe scenario that predicts a low density, negative curvature universe, we investigate the Euclidean vacuum mode functions of a scalar...
Particle Spectrum Created Through Bubble Nucleation (1994)
Yamamoto, Kazuhiro, Tanaka, Takahiro, Sasaki, Misao
Using the multi-dimensional wave function formalism, we investigate the quantum state of a scalar field inside a true vacuum bubble nucleated through false vacuum decay in flat spacetime. We...
Decoherence on Quantum Tunneling in the Multi-Dimensional Wave Function Approach (1994)
We consider fundamental problems on the understanding of the tunneling phenomena in the context of the multi-dimensional wave function. In this paper, we reconsider the quantum state after tunneling...
Shibata, Masaru, Sasaki, Misao, Tagoshi, Hideyuki, Tanaka, Takahiro
Using the Teukolsky and Sasaki-Nakamura equations for the gravitational perturbation of the Kerr spacetime, we calculate the post-Newtonian expansion of the energy and angular momentum luminosities...
Quantum State During and after $O(4)$-Symmetric Bubble Nucleation with Gravitaional Effects (1994)
TANAKA, Takahiro, SASAKI, Misao
We extend our previous analysis of the quantum state during and after $O(4)$-symmetric bubble nucleation to the case including gravitational effects. We find that there exists a simple relationship...
Probability Distribution of Primordial Angular Momentum and Formation of Massive Black Holes (1994)
Susa, Hajime, Sasaki, Misao, Tanaka, Takahiro
We consider the joint probability distribution function for the mass contrast and angular momentum of over-density regions on the proto- galactic scale and investigate the formation of massive black...
General Solutions for Tunneling of Scalar Fields with Quartic Potentials in de Sitter Space (1994)
Sasaki, Misao, Stewart, Ewan D., Tanaka, Takahiro
The tunneling rates for scalar fields with quartic potentials in de Sitter space in the limit of no gravitational back reaction are calculated numerically and the results are fitted by analytic...
Special Quotes Invoke Autocorrelation in Japanese Stock Prices *
Yoshiro Tsutsui, Kenjiro Hirayama, Takahiro Tanaka, Nobutaka Uesugi
It is reported in the present paper that 1-min returns on TOPIX have exhibited significant autocorrelation at 5-min intervals since 1997/1998. Special quotes that are issued whenever there is a price...