Papers

7. "Revisiting timelike geodesics in the Fisher/Janis-Newman-Winicour-Wyman spacetime,"

    Keisuke Ota, Shinpei Kobayashi, Keisuke Nakashi,

    Phys. Rev. D 105 (2022) 2, 024037,

    arXiv: 2110.07503 [gr-qc].

6. "Photon surfaces in less symmetric spacetimes,"

    Yasutaka Koga, Takahisa Igata, Keisuke Nakashi,

    Phys. Rev. D 103 (2021) 4, 044003,

    arXiv: 2011.10234 [gr-qc].

5. "Towards rotating non-circular black holes in string-inspired gravity,"

    Keisuke Nakashi, Masashi Kimura, 

    Phys. Rev. D 102 (2020) 8, 084021,

    arXiv: 2008.04003 [gr-qc]. 

4. "Observability of the innermost stable circular orbit in a near-extremal Kerr black hole,"

    Takahisa Igata, Keisuke Nakashi, Kota Ogasawara,

    Phys. Rev. D 101 (2020) 4, 044044, 

    arXiv:1910.12682 [astro-ph.HE]. 

3. "Effect of a second compact object on stable circular orbits,"

    Keisuke Nakashi and Takahisa Igata,

    Phys. Rev. D 100 (2019) 10, 104006,

    arXiv:1908.10075 [gr-qc]. 

2. "Innermost stable circular orbits in the Majumdar-Papapetrou dihole spacetime,"

    Keisuke Nakashi and Takahisa Igata,

    Phys. Rev. D 99 (2019) 12, 124033,

    arXiv:1903.10121 [gr-qc]. 

1. "Null Geodesics and Repulsive Behavior of Gravity in (2+1)-dimensional Massive Gravity,"

    Keisuke Nakashi, Shinpei Kobayashi, Shu Ueda, Hiromi Saida,

    PTEP 2019 (2019) no.7, 073E02,

    arXiv:1901.06098 [gr-qc].