Tomohiro Harada   Takahisa Igata   Takuma Sato   Bernard Carr   
2021年10月
We completely classify the Friedmann-Lemaître-Robertson-Walker solutions with spatial curvature K=0,±1 for perfect fluids with linear equation of state p=wρ, where ρ and p are the energy density and pressure for the perfect fluid without assuming ...
Igata, T.   Kohri, K.   Ogasawara, K.   
Physical Review D 103(10) 2021年5月 [査読有り]
We consider a situation where a light source orbiting the innermost stable circular orbit (ISCO) of the Kerr black hole is gently falling from the marginally stable orbit due to an infinitesimal perturbation. Assuming that the light source emits p...
We consider the motion of massive and massless particles in a five-dimensional spacetime with a compactified extra-dimensional space where a black hole is localized, i.e., a caged black hole spacetime. We show the existence of circular orbits and ...
Reducing motion of particles to a two-dimensional potential problem, we show that there are stable circular orbits around a squashed Kaluza-Klein black hole with a spherical horizon and multi–Kaluza-Klein black holes with two spherical horizons in...
Journal of Physics: Conference Series 314 012113-012113 2011年9月 [査読有り]
We study stable bound orbits of a free particle around a black ring. Unlike the higher-dimensional black hole case, we find that there exist stable bound orbits in toroidal spiral shape near the ring axis and stable circular orbits on the axis. In...