3.9k citations
Counting papers with at most 25 authors, so collaboration author lists do not stand in for the people here.
- The University of TokyoJP927 papers
- Kyoto UniversityJP365 papers
- High Energy Accelerator Research OrganizationJP235 papers
- Tokyo Institute of TechnologyJP227 papers
- RIKENJP226 papers
- The University of OsakaJP205 papers
- Nagoya UniversityJP182 papers
- Tohoku UniversityJP174 papers
- Kavli Institute for the Physics and Mathematics of the UniverseJP169 papers
- Hiroshima UniversityJP167 papers
- Centre National de la Recherche ScientifiqueFR164 papers
- Japan Aerospace Exploration AgencyJP156 papers
104 papers · 1 filter
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…
Gravitational lensing inside and outside of a marginally unstable photon sphere in a general, static, spherically symmetric, and asymptotically-flat spacetime in strong deflection limits
Naoki Tsukamoto
It is believed that rays bent inside and outside photon spheres could affect partially the black hole shadow images by the Event Horizon Telescope and the rays near photon spheres…
Linear perturbations of dyonic black holes in the lowest-order gauge-invariant scalar-vector-tensor theories
Kitaro Taniguchi, Shunta Nishimura, Naoki Tsukamoto +1
We study linear perturbations on top of the static and spherically symmetric background of dyonic black hole solutions endowed with electric and magnetic charges, as well as a scal…
Neutral particle collisions near Gibbons-Maeda-Garfinkle-Horowitz-Strominger black holes after shadow observations
Naoki Tsukamoto, Ryotaro Kase
A Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) black hole with a magnetic charge (or an electric charge) has noteworthy features that its scalar curvature near the event hor…
Even-parity stability of hairy black holes in gauge-invariant scalar-vector-tensor theories
Chao Zhang, Ryotaro Kase
The gauge-invariant scalar-vector-tensor theories, which catches five degrees of freedom, are valuable for its implications to inflation problems, generation of primordial m…
Constraints on the black-hole charges of M87* and Sagittarius A* by changing rates of photon spheres can be relaxed
Naoki Tsukamoto, Ryotaro Kase
The Event Horizon Telescope (EHT) Collaboration observed ring images called the shadows of M87* and Sagittarius~A* (Sgr~A*), which are supermassive objects in M87 and our galaxy, r…
Hairy black holes in extended Einstein-Maxwell-scalar theories with magnetic charge and kinetic couplings
Kitaro Taniguchi, Shinta Takagishi, Ryotaro Kase
We study black hole (BH) solutions in extended Einstein-Maxwell-scalar theories, which are classified in a subclass of the gauge-invariant scalar-vector-tensor theories. The…
Circular light orbits of a general, static, and spherical symmetrical wormhole with symmetry
Naoki Tsukamoto
Recently, the ring images or the shadow images of the centers of the galaxy M87 and the Milky way have been reported by Event Horizon Telescope Collaboration. It is believed that t…
TESLA-X: An effective method to search for sub-threshold lensed gravitational waves with a targeted population model
Alvin K. Y. Li, Juno C. L. Chan, Heather Fong +3
Strong gravitational lensing can produce copies of gravitational-wave signals from the same source with the same waveform morphologies but different amplitudes and arrival times. S…
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…
The Quasinormal Modes and Isospectrality of Bardeen (Anti-) de Sitter Black Holes
Ying Zhao, Wentao Liu, Chao Zhang +2
Black holes (BHs) exhibiting coordinate singularities but lacking essential singularities throughout the entire spacetime are referred to as regular black holes (RBHs). The initial…
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…
Equilibriums of extremely magnetized compact stars with force-free magnetotunnels
Koji Uryu, Shijun Yoshida, Eric Gourgoulhon +5
We present numerical solutions for stationary and axisymmetric equilibriums of compact stars associated with extremely strong magnetic fields. The interior of the compact stars is…
Odd-parity perturbations of the wormhole-like geometries and quasi-normal modes in Einstein-Æther theory
Chao Zhang, Anzhong Wang, Tao Zhu
The Einstein-ther theory has drawn a lot of attentions in recent years. As a representative case of gravitational theories that break the Lorentz symmetry, it plays an important…
Black hole perturbations in Maxwell-Horndeski theories
Ryotaro Kase, Shinji Tsujikawa
We study the linear stability of black holes in Maxwell-Horndeski theories where a gauge-invariant vector field is coupled to a scalar field with the Lagrangian of full Horn…
First-step experiment in developing optical-spring quantum locking for DECIGO: sensitivity optimization for simulated quantum noise by completing the square
Tomohiro Ishikawa, Yuki Kawasaki, Kenji Tsuji +12
DECi-hertz Interferometer Gravitational Wave Observatory (DECIGO) is a future mission for a space-borne laser interferometer. DECIGO has 1,000-km-long arm cavities mainly to detect…
Universal horizons and black hole spectroscopy in gravitational theories with broken Lorentz symmetry
Chao Zhang, Anzhong Wang, Tao Zhu
The violation of Lorentz invariance (LI) in gravitational theories, which allows superluminal propagations, dramatically alters the causal structure of the spacetime and modifies t…
Generalized Mathisson-Papapetrou-Tulczyjew-Dixon Equations
Takayoshi Ootsuka, Ryoko Yahagi
We derive two generalizations of Mathisson-Papapetrou-Tulczyjew-Dixon equations from Casalbuoni-Brink-Schwarz type pseudoclassical Lagrangians of Majorana spinors on a Riemann-Cart…
Vainshtein screening in Horndeski theories nonminimally and kinetically coupled to ordinary matter
Kitaro Taniguchi, Ryotaro Kase
We study the Vainshtein screening mechanism in Horndeski theories in the presence of a scalar field nonminimally and kinetically coupled to ordinary matter field. A general int…
Relativistic star perturbations in Horndeski theories with a gauge-ready formulation
Ryotaro Kase, Shinji Tsujikawa
We present a general framework for studying the relativistic star perturbations on a static and spherically symmetric background in full Horndeski theories. We take a perfect fluid…
Instability of compact stars with a nonminimal scalar-derivative coupling
Ryotaro Kase, Shinji Tsujikawa
For a theory in which a scalar field has a nonminimal derivative coupling to the Einstein tensor of the form , it is known that there exis…
Stability of relativistic stars with scalar hairs
Ryotaro Kase, Rampei Kimura, Seiga Sato +1
We study the stability of relativistic stars in scalar-tensor theories with a nonminimal coupling of the form , where depends on a scalar field and is the Ricci…
General formulation of cosmological perturbations in scalar-tensor dark energy coupled to dark matter
Ryotaro Kase, Shinji Tsujikawa
For a scalar field coupled to cold dark matter (CDM), we provide a general framework for studying the background and perturbation dynamics on the isotropic cosmological backgro…
Suppressed cosmic growth in coupled vector-tensor theories
Antonio De Felice, Shintaro Nakamura, Shinji Tsujikawa
We study a coupled dark energy scenario in which a massive vector field with broken gauge symmetry interacts with the four-velocity of cold dark matter (CDM) t…