Numerical Modeling of the Coagulation and Porosity Evolution of Dust Aggregates (2009)
Okuzumi, Satoshi, Tanaka, Hidekazu, Sakagami, Masa-aki
Porosity evolution of dust aggregates is crucial in understanding dust evolution in protoplanetary disks. In this study, we present useful tools to study the coagulation and porosity evolution of...
Nishizawa, Atsushi, Taruya, Atsushi, Hayama, Kazuhiro, Kawamura, Seiji, Sakagami, Masa-aki
In a general metric theory of gravitation in four dimensions, six polarizations of a gravitational wave are allowed: two scalar and two vector modes, in addition to two tensor modes in general...
Resonant speed meter for gravitational wave detection (2008)
Nishizawa, Atsushi, Kawamura, Seiji, Sakagami, Masa-aki
Gravitational-wave detectors have been well developed and operated with high sensitivity. However, they still suffer from mirror displacement noise. In this paper, we propose a resonant speed meter,...
Okuzumi, Satoshi, Ioka, Kunihito, Sakagami, Masa-aki
We investigate the nonlinear evolution of black hole ringdown in the framework of higher-order metric perturbation theory. By solving the initial-value problem of a simplified nonlinear field model...
Nishizawa, Atsushi, Kawamura, Seiji, Akutsu, Tomotada, Arai, Koji, Yamamoto, Kazuhiro, Tatsumi, Daisuke, ...
Recently, observational searches for gravitational wave background (GWB) have been developed and given constraints on the energy density of GWB in a broad range of frequencies. These constraints have...
Nishizawa, Atsushi, Kawamura, Seiji, Akutsu, Tomotada, Arai, Koji, Yamamoto, Kazuhiro, Tatsumi, Daisuke, ...
Recently, observational searches for gravitational wave background (GWB) have been developed and given direct and indirect constraints on the energy density of GWB in a broad range of frequencies....
Nishizawa, Atsushi, Kawamura, Seiji, Akutsu, Tomotada, Arai, Koji, Yamamoto, Kazuhiro, Tatsumi, Daisuke, ...
Recently, observational searches for gravitational wave background (GWB) have developed and given direct and indirect constraints on the energy density of GWB in a broad range of frequencies. These...
Quantum Noise in Differential-type Gravitational-wave Interferometer and Signal Recycling (2007)
Nishizawa, Atsushi, Kawamura, Seiji, Sakagami, Masa-aki
There exists the standard quantum limit (SQL), derived from Heisenberg's uncertainty relation, in the sensitivity of laser interferometer gravitational-wave detectors. However, in the context of a...
Quasinormal ringing of acoustic black holes in Laval nozzles: Numerical simulations (2007)
Okuzumi, Satoshi, Sakagami, Masa-aki
Quasinormal ringing of acoustic black holes in Laval nozzles is discussed. The equation for sounds in a transonic flow is written into a Schr\"{o}dinger-type equation with a potential barrier, and...
Antonov problem and quasi-equilibrium states in N-body system (2005)
Taruya, Atsushi, Sakagami, Masa-aki
In this paper, a quantitative characterization for the evolutionary sequence of stellar self-gravitating system is investigated, focusing on the pre-collapse stage of the long-term dynamical...
Massive quasi-normal mode (2004)
Ohashi, Akira, Sakagami, Masa-aki
This paper purposes to study quasi-normal modes due to massive scalar fields. We, in particular, investigate the dependence of QNM frequencies on the field mass. By this research, we find that there...
CFT description of three-dimensional Hawking-Page transition (2004)
Kurita, Yasunari, Sakagami, Masa-aki
We construct a phenomenological conformal field theory (CFT) model of the three-dimensional Hawking-Page transition. We find that free fermion CFT models on the boundary torus give a description of...
Self-gravitating Stellar Systems and Non-extensive Thermostatistics (2003)
Sakagami, Masa-aki, Taruya, Atsushi
After introducing the fundamental properties of self-gravitating systems, we present an application of Tsallis' generalized entropy to the analysis of their thermodynamic nature. By extremizing the...
Taruya, Atsushi, Sakagami, Masa-aki
With particular attention to the recently postulated introduction of a non-extensive generalization of Boltzmann-Gibbs statistics, we study the long-term stellar dynamical evolution of...
Taruya, Atsushi, Sakagami, Masa-aki
We revisit the issues on the thermodynamic property of stellar self-gravitating system arising from Tsallis' non-extensive entropy. Previous papers (Taruya & Sakagami, Physica A 307 (2002) 185...
Quasi-normal modes of D3-brane Black Holes (2002)
Kurita, Yasunari, Sakagami, Masa-aki
We investigate a method to evaluate quasi-normal modes of D3-brane black holes by wave interpretation of fields on D3-brane based on the Feynman's space-time approach. We perturbatively solve the...
Hawking Radiation in Laboratories (2001)
Sakagami, Masa-aki, Ohashi, Akira
We propose an experimental model using the Laval nozzle of a sonic analogue of the Hawking radiation. We observe a power spectrum of the out-going wave emitted from the vicinity a sonic horizon in...
Gravothermal Catastrophe and Generalized Entropy of Self-Gravitating Systems (2001)
Taruya, Atsushi, Sakagami, Masa-aki
We present a first physical application of Tsallis' generalized entropy to the thermodynamics of self-gravitating systems. The stellar system confined in a spherical cavity of radius $r_e$ exhibits...
Perturbative analysis of non-singular cosmological model (1999)
Kawai, Shinsuke, Sakagami, Masa-aki, Soda, Jiro
A stability analysis is made for a non-singular pre-big-bang like cosmological model based on 1-loop corrected string effective action. Its homogeneous and isotropic solution realizes non-singular...
Novel Instability in Superstring Cosmology (1998)
Soda, Jiro, Sakagami, Masa-aki, Kawai, Shinsuke
As a most promising candidate for quantum theory of the gravity, the superstring theory has attracted many researchers including cosmologists. It is expected that the cosmological initial singularity...
Instability of 1-loop superstring cosmology (1998)
Kawai, Shinsuke, Sakagami, Masa-aki, Soda, Jiro
A stability analysis is made in the context of the previously discovered non-singular cosmological solution from 1-loop corrected superstring effective action. We found that this solution has an...
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...