Head-on collision and merging entropy of black holes: reconsideration of Hawking's inequality (2009)
We evaluate how much energy can be converted into gravitational radiation in head-on collision of black holes. We estimate it by the area theorem of black hole horizon incorporating merging entropy...
Half period theorem of binary black holes (2008)
Merging event horizons of the binary black holes will be investigated. Though recent development of the numerical study of the binary black hole coalescence has shown that their apparent horizons can...
Nonlinear Evolution Of The Genus Statistics With Zel'dovich Approximation (2007)
Naoki Seto, Takahiko Matsubara, Masaru Siino
Evolution of genus density is calculated from Gaussian initial conditions using Zel'dovich approximation. A new approach is introduced which formulates the desired quantity in a rotationally...
Nucleation of Universe in (2+1)-Dimensional Gravity with Negative Cosmological Constant (2007)
Yoshihisa Fujiwara, Saburo Higuchi, Akio Hosoya, Takashi Mishima, Masaru Siino
We investigate the nucleation of universe in a (2+1)-dimensional gravity model with negative cosmological constant. There are a variety of universes born from nothing by quantum tunneling. Utilizing...
Stable Topologies of Event Horizon (2007)
In our previous work, it was shown that the topology of an event horizon (EH) is determined by the past endpoints of the EH. A torus EH (the collision of two EH) is caused by the two-dimensional...
Topology Changes in (2+1)-Dimensional Quantum Gravity (2007)
Yoshihisa Fujiwara, Saburo Higuchi, Akio Hosoya, Takashi Mishima, Masaru Siino
We study topology changing processes in (2+1)-dimensional quantum gravity with negative cosmological constant. By playing the `gluing-many-polyhedra game' for hyperbolic geometry, we explicitly...
Topology Change of Black Holes (2007)
The topological structure of the event horizon has been investigated in terms of the Morse theory. The elementary process of topological evolution can be understood as a handle attachment. It has...
Operator geometry and algebraic gravity (2006)
An algebraic formulation of general relativity is proposed. The formulation is applicable to quantum gravity and noncommutative space. To investigate quantum gravity we develop the canonical...
Tomizawa, Shinya, Siino, Masaru
We investigated the relation between the behavior of gravitational wave at late time and the limit structure of future null infinity tangent which will determine the topology of the event horizon far...
The crease set of an event horizon is studied in a spacetime with discrete or continuous symmetry. It determines possible topologies on spatial sections of an event horizon. We thereby investigate...
Topological classification of black Hole: Generic Maxwell set and crease set of horizon (2004)
Siino, Masaru, Koike, Tatsuhiko
The crease set of an event horizon or a Cauchy horizon is an important object which determines qualitative properties of the horizon. In particular, it determines the possible topologies of the...
Topological derivation of Black Hole entropy by analogy with a chain polymer (2001)
The generic crease set of an event horizon possesses anisotropic structure though most of black holes are dynamically stable. This fact suggests that a generic almost spherical black hole has a very...
Thurston's Geometrization Conjecture and cosmological models (2000)
Yasuno, Katsuhito, Koike, Tatsuhiko, Siino, Masaru
We investigate a class of spatially compact inhomogeneous spacetimes. Motivated by Thurston's Geometrization Conjecture, we give a formulation for constructing spatially compact composite spacetimes...
The topology of the event horizon (TOEH) is usually believed to be a sphere. Nevertheless, some numerical simulations of gravitational collapse with a toroidal event horizon or the collision of event...
Stable Topologies of Event Horizon (1997)
In our previous work, it was shown that the topology of an event horizon (EH) is determined by the past endpoints of the EH. A torus EH (the collision of two EH) is caused by the two-dimensional...
Topology of Event Horizon (1997)
The topologies of event horizons are investigated. Considering the existence of the endpoint of the event horizon, it cannot be differentiable. Then there are the new possibilities of the topology of...
Nonlinear Evolution of the Genus Statistics with Zel'dovich Approximation (1996)
Seto, Naoki, Yokoyama, Jun'ichi, Matsubara, Takahiko, Siino, Masaru
Evolution of genus density is calculated from Gaussian initial conditions using Zel'dovich approximation. A new approach is introduced which formulates the desired quantity in a rotationally...
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...
Quantum Stability of (2+1)-Spacetimes with Non-Trivial Topology (1996)
Quantum fields are investigated in the (2+1)-open-universes with non-trivial topologies by the method of images. The universes are locally de Sitter spacetime and anti-de Sitter spacetime. In the...
Four Dimensional Quantum Topology Changes of Spacetimes (1995)
Ding, Shuxue, Maeda, Yasushige, Siino, Masaru
We investigate topology changing processes in the WKB approximation of four dimensional quantum cosmology with a negative cosmological constant. As Riemannian manifolds which describe quantum...
Topology Changes by Quantum Tunneling in Four Dimensions (1994)
Shuxue, Ding, Maeda, Yasushige, Siino, Masaru
We investigate topology-changing processes in 4-dimensional quantum gravity with a negative cosmological constant. By playing the ``gluing-polytope game" in hyperbolic geometry, we explicitly...
Causal Feature of Central Singularity and Gravitational Mass (1993)
Koike, Tatsuhiko, Onozawa, Hisashi, Siino, Masaru
Mass of singularity is defined, and its relation to whether the singularity is spacelike, timelike or null is discussed for spherically symmetric spacetimes. It is shown that if the mass of...
We present a compactified version of the 3-dimensional black hole recently found by considering extra identifications and determine the analytical continuation of the solution beyond its coordinate...
Local Structure of Numerically Generated Worm Hole Spacetime (1993)
Nambu, Yasusada, Siino, Masaru
We investigate the evolution of the apparent horizons in a numerically gererated worm hole spacetime. The behavior of the apparent horizons is affected by the dynamics of the matter field. By using...