Igata, T.   Ishihara, H.   Yasunishi, Y.   
Physical Review D 100(4) 2019年8月 [査読有り]
We investigate the spherical photon orbits in near-extremal Kerr spacetimes. We show that the spherical photon orbits with impact parameters in a finite range converge on the event horizon. Furthermore, we demonstrate that the Weyl curvature near ...
Cardoso, V.   Igata, T.   Ishibashi, A.   Ueda, K.   
Physical Review D 100(4) 2019年8月 [査読有り]
We develop a new perturbation method to study the dynamics of massive tensor fields on extremal and near-extremal static black hole spacetimes in arbitrary dimensions. On such backgrounds, one can classify the components of massive tensor fields i...
We investigate the positions of stable circular massive particle orbits in the Majumdar-Papapetrou dihole spacetime with equal mass. In terms of qualitative differences of their sequences, we classify the dihole separation into five ranges and fin...
Igata, T.   Ishihara, H.   Tsuchiya, M.   Yoo, C.-M.   
Physical Review D 98(6) 2018年9月 [査読有り]
We analyze rigidly rotating Nambu-Goto strings in the Kerr spacetime, particularly focusing on the strings sticking in the horizon. From the regularity on the horizon, we find the condition for sticking in the horizon, which is consistent with the...
Progress of Theoretical and Experimental Physics 2018(6) 2018年6月 [査読有り]
Scale invariance in the theory of classical mechanics can be induced from the scale invariance of background fields. In this paper we consider the relation between the scale invariance and the constants of particle motion in a self-similar spaceti...
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...