All vacuum near horizon geometries in arbitrary dimensions (2009)
Hollands, Stefan, Ishibashi, Akihiro
We explicitly construct all stationary, extremal near horizon geometries in $D$ dimensions that satisfy the vacuum Einstein equations, and that have $D-3$ commuting rotational symmetries. Our work...
Spherically symmetric black holes in minimally modified self-dual gravity (2009)
Ishibashi, Akihiro, Speziale, Simone
We discuss spherically symmetric black holes in the modified self-dual theory of gravity recently studied by Krasnov, obtained adding a Weyl-curvature dependent `cosmological term' to the Plebanski...
Tomizawa, Shinya, Yasui, Yukinori, Ishibashi, Akihiro
We show a uniqueness theorem for charged rotating black holes in the bosonic sector of five-dimensional minimal supergravity. More precisely, under the assumptions of the existence of two commuting...
Hollands, Stefan, Ishibashi, Akihiro
All known stationary black hole solutions in higher dimensions possess additional rotational symmetries in addition to the stationary Killing field. Also, for all known stationary solutions, the...
Charged Black Holes in a Rotating Gross-Perry-Sorkin Monopole Background (2008)
Tomizawa, Shinya, Ishibashi, Akihiro
We present a new class of stationary charged black hole solutions to five-dimensional Einstein-Maxwell-Chern-Simons theories. We construct the solutions by utilizing so called the squashing...
Higher Dimensional Bondi Energy with a Globally Specified Background Structure (2007)
A higher (even spacetime) dimensional generalization of the Bondi energy has recently been proposed by gr-qc/0304054 within the framework of conformal infinity and Hamiltonian formalizm. The gauge...
Causality violation and singularities (2007)
Kengo Maeda, Akihiro Ishibashi
We show that singularities necessarily occur when a boundary of causality violating set exists in a space-time under the physically suitable assumptions except the global causality condition in the...
A Higher Dimensional Stationary Rotating Black Hole Must be Axisymmetric (2006)
Hollands, Stefan, Ishibashi, Akihiro, Wald, Robert M.
A key result in the proof of black hole uniqueness in 4-dimensions is that a stationary black hole that is ``rotating''--i.e., is such that the stationary Killing field is not everywhere normal to...
Asymptotically AdS brane black holes (2005)
Galfard, Christophe, Germani, Cristiano, Ishibashi, Akihiro
We study the possibility of having a static, asymptotically AdS black hole localized on a braneworld with matter fields, within the framework of the Randall and Sundrum scenario. We attempt to look...
Can the Acceleration of Our Universe Be Explained by the Effects of Inhomogeneities? (2005)
Ishibashi, Akihiro, Wald, Robert M.
No. It is simply not plausible that cosmic acceleration could arise within the context of general relativity from a back-reaction effect of inhomogeneities in our universe, without the presence of a...
On the stability of naked singularities (2004)
Gibbons, Gary W., Hartnoll, Sean A., Ishibashi, Akihiro
We study the linearised stability of the nakedly singular negative mass Schwarzschild solution against gravitational perturbations. There is a one parameter family of possible boundary conditions at...
On the stability of black holes and naked singularities in static spacetimes (2004)
We briefly review the recent results of the stability analysis of the Schwarzschild metric with either positive or negative mass parameter. For the positive mass (black hole) case, the metric is...
Dynamics in Non-Globally-Hyperbolic Static Spacetimes III: Anti-de Sitter Spacetime (2004)
Ishibashi, Akihiro, Wald, Robert M.
In recent years, there has been considerable interest in theories formulated in anti-de Sitter (AdS) spacetime. However, AdS spacetime fails to be globally hyperbolic, so a classical field satisfying...
Topology and Signature Changes in Braneworlds (2004)
Gibbons, Gary W., Ishibashi, Akihiro
It has been believed that topology and signature change of the universe can only happen accompanied by singularities, in classical, or instantons, in quantum, gravity. In this note, we point out...
Stability of Generalised Static Black Holes in Higher Dimensions (2003)
Kodama, Hideo, Ishibashi, Akihiro
We discuss the stability of (charged) static black holes in higher-dimensional spacetimes with and without cosmological constant by using gauge-invariant master equations of the Schroedinger equation...
Asymptotic flatness at null infinity in higher dimensional gravity (2003)
Hollands, Stefan, Ishibashi, Akihiro
We give a geometrical definition of the asymptotic flatness at null infinity in spacetimes of even dimension $d$ greater than 4 within the framework of conformal infinity. Our definition is shown to...
Kodama, Hideo, Ishibashi, Akihiro
We extend the formulation for perturbations of maximally symmetric black holes in higher dimensions developed by the present authors in a previous paper (hep-th/0305147) to a charged black hole...
Stability of Higher-Dimensional Schwarzschild Black Holes (2003)
Ishibashi, Akihiro, Kodama, Hideo
We investigate the classical stability of the higher-dimensional Schwarzschild black holes against linear perturbations, in the framework of a gauge-invariant formalism for gravitational...
Kodama, Hideo, Ishibashi, Akihiro
We show that in four or more spacetime dimensions, the Einstein equations for gravitational perturbations of maximally symmetric vacuum black holes can be reduced to a single 2nd-order wave equation...
Ishibashi, Akihiro, Wald, Robert M.
It was previously shown by one of us that in any static, non-globally-hyperbolic, spacetime it is always possible to define a sensible dynamics for a Klein-Gordon scalar field. The prescription...
Asymptotic Flatness and Bondi Energy in Higher Dimensional Gravity (2003)
Hollands, Stefan, Ishibashi, Akihiro
We give a general geometric definition of asymptotic flatness at null infinity in $d$-dimensional general relativity ($d$ even) within the framework of conformal infinity. Our definition is arrived...
Thick domain walls around a black hole (2002)
Morisawa, Yoshiyuki, Ida, Daisuke, Ishibashi, Akihiro, Nakao, Ken-ichi
We discuss the gravitationally interacting system of a thick domain wall and a black hole. We numerically solve the scalar field equation in the Schwarzschild spacetime and obtain a sequence of...
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...
Naked Singularity and Thunderbolt (2002)
Ishibashi, Akihiro, Hosoya, Akio
We consider quantum theoretical effects of the sudden change of the boundary conditions which mimics the occurrence of naked singularities. For a simple demonstration, we study a massless scalar...
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...
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....
Convex Functions and Spacetime Geometry (2000)
Gibbons, Gary W., Ishibashi, Akihiro
Convexity and convex functions play an important role in theoretical physics. To initiate a study of the possible uses of convex functions in General Relativity, we discuss the consequences of a...
Instability of a membrane intersecting a black hole (2000)
Higaki, Susumu, Ishibashi, Akihiro, Ida, Daisuke
The stability of a Nambu-Goto membrane at the equatorial plane of the Reissner-Nordstr{\o}m-de Sitter spacetime is studied. The covariant perturbation formalism is applied to study the behavior of...
Thick Domain Walls Intersecting a Black Hole (2000)
Morisawa, Yoshiyuki, Yamazaki, Ryo, Ida, Daisuke, Ishibashi, Akihiro, Nakao, Ken-ichi
We discuss the gravitationally interacting system of a thick domain wall and a black hole. We numerically solve the scalar field equation in the Schwarzschild spacetime and show that there exist...
Brane World Cosmology - Gauge-Invariant Formalism for Perturbation (2000)
Kodama, Hideo, Ishibashi, Akihiro, Seto, Osamu
In the present paper the gauge-invariant formalism is developed for perturbations of the brane-world model in which our universe is realized as a boundary of a higher-dimensional spacetime. For the...
Nakamura, Kouji, Ishibashi, Akihiro, Ishihara, Hideki
We study the perturbative dynamics of an infinite gravitating Nambu-Goto string within the general-relativistic perturbation framework. We develop the gauge invariant metric perturbation on a...
Who's Afraid of Naked Singularities? (1999)
Ishibashi, Akihiro, Hosoya, Akio
To probe naked spacetime singularities with waves rather than with particles we study the well-posedness of initial value problems for test scalar fields with finite energy so that the natural...
Chronology Protection and Non-Naked Singularity (1998)
Maeda, Kengo, Ishibashi, Akihiro, Narita, Makoto
We test the chronology protection conjecture in classical general relativity by investigating finitely vicious space-times. First we present singularity theorems in finitely vicious space-times by...
Equation of motion for a domain wall coupled to gravitational field (1998)
Ishibashi, Akihiro, Ishihara, Hideki
The equation of motion for a domain wall coupled to gravitational field is derived from the Nambu-Goto action. The domain wall is treated as a source of gravitational field. The perturbed equation is...
Upper bound for entropy in asymptotically de Sitter space-time (1997)
Maeda, Kengo, Koike, Tatsuhiko, Narita, Makoto, Ishibashi, Akihiro
We investigate nature of asymptotically de Sitter space-times containing a black hole. We show that if the matter fields satisfy the dominant energy condition and the cosmic censorship holds in the...
On the perturbation of domain wall coupled to gravitational waves (1997)
Ishibashi, Akihiro, Ishihara, Hideki
The equation of motion for domain wall coupled to gravitational field is derived. The domain wall is treated as a source of gravitational field around the wall. The perturbed equation is also...
Bubble wall perturbations coupled with gravitational waves (1997)
Ishibashi, Akihiro, Ishihara, Hideki
We study a coupled system of gravitational waves and a domain wall which is the boundary of a vacuum bubble in de Sitter spacetime. To treat the system, we use the metric junction formalism of...
Strong Cosmic Censorship and Causality Violation (1996)
Maeda, Kengo, Ishibashi, Akihiro
We investigate the instability of the Cauchy horizon caused by causality violation in the compact vacuum universe with the topology $B\times {\bf S}^{1}\times {\bf R}$, which Moncrief and Isenberg...
Causality violation and singularities (1996)
Maeda, Kengo, Ishibashi, Akihiro
We show that singularities necessarily occur when a boundary of causality violating set exists in a space-time under the physically suitable assumptions except the global causality condition in the...
Compact hyperbolic universe and singularities (1996)
Ishibashi, Akihiro, Koike, Tatsuhiko, Siino, Masaru, Kojima, Sadayoshi
Recently many people have discussed the possibility that the universe is hyperbolic and was in an inflationary phase in the early stage. Under these assumptions, it is shown that the universe cannot...