251 citations · 2.2k across the 40 of their papers we have counts for
40 papers
Gravitational lensing outside and inside of a marginally unstable photon sphere at a -symmetric wormhole throat in strong deflection limits
Naoki Tsukamoto
The deflection angles of rays diverge logarithmically near outside and inside of a photon sphere in usual strong deflection limits and the rays near the photon sphere could be dete…
Strong-deflection expansion of the deflection angle near a degenerate photon sphere
Takahisa Igata, Tadashi Sasaki, Naoki Tsukamoto
We present a strong-deflection expansion for the deflection angle of light rays scattered near a degenerate photon sphere in asymptotically flat, static, and spherically symmetric…
Comment on "Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A*"
Naoki Tsukamoto
Vagnozzi et al. constrained the additional parameter of spacetimes with a photon sphere from the observation of the shadow of Sagittarius A* under the assumption that a distance to…
Relation between circular photon orbits and the stability of wormholes with the thin shell of a barotropic fluid
Naoki Tsukamoto, Takafumi Kokubu
We cut a general, static, spherically symmetric spacetime and paste its copy to make a wormhole with a thin shell of any barotropic fluid in general relativity. We show that the st…
Gravitational lensing by using the 0th order of affine perturbation series of the deflection angle of a ray near a photon sphere
Naoki Tsukamoto
The 0th order of affine perturbation series of the deflection angle of a ray near a photon sphere is more accurate than a deflection angle in a strong deflection limit, which is us…
Affine perturbation series of the deflection angle of a ray near the photon sphere of a Reissner-Nordström black hole
Naoki Tsukamoto
We investigate the affine perturbation series of the deflection angle of a ray near the photon sphere of an extreme Reissner-Nordström black hole. We compare the 0th and 1st orders…