117 citations · 295 across the 15 of their papers we have counts for
15 papers
Parametrized-Post-Newtonian Test of Black Hole Spacetime for Galactic Center Massive Black Hole Sgr A*: Formulation and Fitting
Hiromi Saida, Sena A. Matsui, Tsutomu T. Takeuchi +4
We have performed a parametrized post-Newtonian (PPN) test of a black hole spacetime using observational data of the star S0-2/S2 orbiting the massive black hole at our galactic ce…
Light deflection in Observation: Angle differences between two null geodesics on the de Sitter spacetime with multi-lensing objects
Rio Saitou, Hiromi Saida
We derive angle differences between two null geodesics, propagating from light sources to an observer, on the de Sitter spacetime with multi-lensing objects. Assuming the lensing o…
Constraints on the dark mass distribution surrounding Sgr A*: simple analysis for the redshift of photons from orbiting stars
Yohsuke Takamori, Shogo Nishiyama, Takayuki Ohgami +3
Sagittarius A* (Sgr A*) is the central supermassive black hole with the mass in the Milky Way and stars are orbiting around it. In May 2018, one of th…
Stochastic approach to de Sitter instability and eternal inflation
Rio Saitou
We investigate when effective theories of a scalar field on (quasi-)de Sitter background break down through the stochastic formalism. We derive the Fokker-Planck equation leaving t…
Inflationary spectral tilts as a result of the dilatation symmetry breaking
Pisin Chen, Jiro Matsumoto, Rio Saitou
We derive the spectral indices and their runnings of single inflation models by a new approach. We perform a dilatation transformation to the linear cosmological perturbations and…
Generic analysis of kinetically driven inflation
Rio Saitou
We perform a model-independent analysis of kinetically driven inflation (KDI) which (partially) includes Generalized G-inflation and Ghost inflation. We evaluate the background evo…
de Sitter spacetime with a Becchi-Rouet-Stora quartet
Rio Saitou, Yungui Gong
We generalize the topological model recently proposed and investigate the cosmological perturbations of the model. The model has an exact de Sitter background solution associated w…
Canonical invariance of spatially covariant scalar-tensor theory
Rio Saitou
We investigate invariant canonical transformations of a spatially covariant scalar-tensor theory of gravity, called the XG theory, by which the action or the Hamiltonian and the pr…
Ghost inflation and de Sitter entropy
Sadra Jazayeri, Shinji Mukohyama, Rio Saitou +1
In the setup of ghost condensation model the generalized second law of black hole thermodynamics can be respected under a radiatively stable assumption that couplings between the f…
Derivative-dependent metric transformation and physical degrees of freedom
Guillem Domènech, Shinji Mukohyama, Ryo Namba +3
We study metric transformations which depend on a scalar field and its first derivatives and confirm that the number of physical degrees of freedom does not change under such t…
A general method for the construction of stable Galileon models consistent with the Planck data results
Rio Saitou, Emilio Elizalde
The reconstruction procedure, which has proven quite useful to obtain viable models of the universe evolution, is here employed in order to construct inflation models. It has the a…
Hamiltonian analysis of nonprojectable Hořava-Lifshitz gravity with symmetry
Shinji Mukohyama, Ryo Namba, Rio Saitou +1
We study the nature of constraints and count the number of degrees of freedom in the nonprojectable version of the extension of Hořava-Lifshitz gravity, using the standard m…
Hamiltonian structure of scalar-tensor theories beyond Horndeski
Chunshan Lin, Shinji Mukohyama, Ryo Namba +1
We study the nature of constraints and the Hamiltonian structure in a scalar-tensor theory of gravity recently proposed by Gleyzes, Langlois, Piazza and Vernizzi (GLPV). For the si…
Stable phantom-divide crossing in two scalar models with matter
Rio Saitou, Shin'ichi Nojiri
We construct cosmological models with two scalar fields, which has the structure as in the ghost condensation model or k-essence model. The models can describe the stable phantom c…
The unification of inflation and late-time acceleration in the frame of -essence
Rio Saitou, Shin'ichi Nojiri
By using the formulation of the reconstruction, we explicitly construct models of -essence, which unify the inflation in the early universe and the late accelerating expansion o…