117 citations · 1k across the 40 of their papers we have counts for
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No Smooth Spacetime in Lorentzian Quantum Cosmology and Trans-Planckian Physics
Hiroki Matsui, Shinji Mukohyama, Atsushi Naruko
In minisuperspace quantum cosmology, the Lorentzian path integral formulations of the no-boundary and tunneling proposals have recently been analyzed. But it has been pointed out t…
Ostrogradsky mode in scalar-tensor theories with higher-order derivative couplings to matter
Atsushi Naruko, Ryo Saito, Norihiro Tanahashi +1
A metric transformation is a tool to find a new theory of gravity beyond general relativity. The gravity action is guaranteed to be free from a dangerous Ostrogradsky mode as long…
DeWitt boundary condition is consistent in Hořava-Lifshitz quantum gravity
Hiroki Matsui, Shinji Mukohyama, Atsushi Naruko
In quantum cosmology the DeWitt boundary condition is a proposal to set the wave function of the universe to vanish at the classical big-bang singularity. In this Letter, we show t…
Testing the Non-circularity of the Spacetime around Sagittarius A* with Orbiting Pulsars
Yohsuke Takamori, Atsushi Naruko, Yusuke Sakurai +3
A disformal Kerr black hole solution is a rotating black hole solution in a modified gravity theory which breaks the circular condition of spacetime differently from the case of th…
Backreaction of Mass and Angular Momentum Accretion on Black Holes: General Formulation of the Metric Perturbations and Application to the Blandford-Znajek Process
Masashi Kimura, Tomohiro Harada, Atsushi Naruko +1
We study the metric backreaction of mass and angular momentum accretion on black holes. We first develop the formalism of monopole and dipole linear gravitational perturbations aro…
Could the black hole singularity be a field singularity?
Guillem Domènech, Atsushi Naruko, Misao Sasaki +1
In the wake of interest to find black hole solutions with scalar hair, we investigate the effects of disformal transformations on static spherically symmetric space-times with a no…