Harada, T.   Carr, B.J.   Igata, T.   
Classical and Quantum Gravity 35(10) 105011-105011 2018年5月 [査読有り]
We completely classify Friedmann–Lemaître–Robertson–Walker solutions with spatial curvature and equation of state , according to their conformal structure, singularities and trapping horizons. We do not assume any energy conditions and allow , the...
Geometrical symmetry in a spacetime can generate test solutions to the Maxwell equation. We demonstrate that the source-free Maxwell equation is satisfied by any generator of spacetime self-similarity---a proper homothetic vector---identified with...
Progress of Theoretical and Experimental Physics 2018(3) 2018年3月 [査読有り]
From a spacetime perspective, the dynamics of magnetic field lines of force-free electromagnetic fields can be rewritten into a quite similar form for the dynamics of strings, i.e., dynamics of “field sheets”. Using this formalism, we explicitly s...
Ogasawara, K.   Harada, T.   Miyamoto, U.   Igata, T.   
Physical Review D 95(12) 2017年6月 [査読有り]
We consider a head-on collision of two massive particles that move in the equatorial plane of an extremal Kerr black hole, which results in the production of two massless particles. Focusing on a typical case, where both of the colliding particles...
Kinoshita, S.   Igata, T.   Tanabe, K.   
Physical Review D 94(12) 2016年12月 [査読有り]
In this paper, we show that a rigidly rotating string can extract the rotational energy from a rotating black hole. We consider Nambu-Goto strings stationary with respect to a corotating Killing vector with an uniform angular velocity ω in the Ker...
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...