59 citations · 168 across the 10 of their papers we have counts for
10 papers
Violation of the Leggett-Garg inequality in photon-graviton conversion
Kimihiro Nomura, Akira Taniguchi, Kazushige Ueda
The Leggett-Garg inequality (LGI) is a temporal analogue of Bell's inequality and provides a quantitative test of the nonclassicality of a system through its violation. We analytic…
Imprints of Dark Photons on Gravitational Wave Polarizations
Kimihiro Nomura, Jiro Soda, Kazushige Ueda +1
We study conversion processes between gravitons and dark photons and reveal the effects of dark photons on the polarization of gravitational waves. Considering cosmological dark ma…
Hellings-Downs curve deformed by ultralight vector dark matter
Hidetoshi Omiya, Kimihiro Nomura, Jiro Soda
Pulsar timing arrays (PTAs) provide a way to detect gravitational waves (GWs) at nanohertz frequencies. To ensure the detection of GWs, observational data must exhibit the Hellings…
Entropy Bound and a Geometrically Nonsingular Universe
Takamasa Kanai, Kimihiro Nomura, Daisuke Yoshida
Bousso's entropy bound is a conjecture that the entropy through a null hypersurface emanating from a two-dimensional surface with a nonpositive expansion is bounded by the area of…
Observing axions through photon ring dimming of black holes
Kimihiro Nomura, Kaishu Saito, Jiro Soda
It is known that magnetic fields exist near black holes and photons can go around black holes due to strong gravity. Utilizing these facts, we can probe hypothetical pseudoscalar p…
Implications of the singularity theorem for the size of a nonsingular universe
Kimihiro Nomura, Daisuke Yoshida
A general property of universes without initial singularity is investigated based on the singularity theorem, assuming the null convergence condition and the global hyperbolicity.…
Quasinormal modes of charged black holes with corrections from nonlinear electrodynamics
Kimihiro Nomura, Daisuke Yoshida
We study quasinormal modes related to gravitational and electromagnetic perturbations of spherically symmetric charged black holes in nonlinear electrodynamics. Beyond the linear M…
Past extendibility and initial singularity in Friedmann-Lemaître-Robertson-Walker and Bianchi I spacetimes
Kimihiro Nomura, Daisuke Yoshida
We study past-directed extendibility of Friedmann-Lemaître-Robertson-Walker (FLRW) and Bianchi type I spacetimes with a scale factor vanishing in the past. We give criteria for det…
Stability of magnetic black holes in general nonlinear electrodynamics
Kimihiro Nomura, Daisuke Yoshida, Jiro Soda
We study the perturbative stability of magnetic black holes in a general class of nonlinear electrodynamics, where the Lagrangian is given by a general function of the field streng…
Pulsar timing residual induced by ultralight vector dark matter
Kimihiro Nomura, Asuka Ito, Jiro Soda
We study the ultralight vector dark matter with a mass around . The vector field oscillating coherently on galactic scales induces oscillations of the spacet…