120 citations · 559 across the 20 of their papers we have counts for
20 papers
The Dynamics of Three-Planet Systems: an Approach from Dynamical System
Bungo Shikita, Hiroko Koyama, Shoichi Yamada
We study in detail the motions of three planets interacting with each other under the influence of a central star. It is known that the system with more than two planets becomes un…
Chaotic motion of Charged Particles in an Electromagnetic Field Surrounding a Rotating Black Hole
Masaaki Takahashi, Hiroko Koyama
The observational data from some black hole candidates suggest the importance of electromagnetic fields in the vicinity of a black hole. Highly magnetized disk accretion may play a…
Dynamical response to supernova-induced gas removal in spiral galaxies with dark matter halo
Hiroko Koyama, Masahiro Nagashima, Takayuki Kakehata +1
We investigate the dynamical response, in terms of disc size and rotation velocity, to mass loss by supernovae in the evolution of spiral galaxies. A thin baryonic disc having the…
Gravitational Wave Signals from Chaotic System: A Point Mass with A Disk
Kenta Kiuchi, Hiroko Koyama, Kei-ichi Maeda
We study gravitational waves from a particle moving around a system of a point mass with a disk in Newtonian gravitational theory. A particle motion in this system can be chaotic w…
1/f fluctuations in spinning-particle motions around Schwarzschild black hole
Hiroko Koyama, Kenta Kiuchi, Tetsuro Konishi
We study the properties of chaos in the motions of a spinning test particle in Schwarzschild spacetime. We characterize the chaos using the power spectrum of the time series of …
Clusters die hard: Time-correlated excitation in the Hamiltonian Mean Field model
Hiroko Koyama, Tetsuro Konishi, Stefano Ruffo
The Hamiltonian Mean Field (HMF) model has a low-energy phase where particles are trapped inside a cluster. Here, we investigate some properties of the trapping/untrapping mech…