47 citations · 236 across the 24 of their papers we have counts for
25 papers
Decoherence of the quantum superradiant cloud from graviton emission
Lingyun Fu, Hidetoshi Omiya, Takahiro Tanaka +1
Black hole superradiance amplifies vacuum fluctuations into a macroscopic cloud of a massive bosonic field around a rotating black hole. Under free evolution, the quantum cloud is…
Dynamics and Frequency Conversion of Accreting Axion Clouds
Ximeng Li, Zhen Zhong, Yifan Chen +3
Axion fields can form exponentially growing gravitational clouds around compact objects through self-interaction-driven relaxation of ambient axion waves. As the field amplitude ap…
The Challenge of Detecting Quantum Nature of Gravitational Waves
Yu Miyauchi, Hidetoshi Omiya, Atsuhisa Ota +2
We investigate whether squeezing can provide an observable signature of quantum gravitational waves. Because a realistic detector couples only to a particular wave-packet mode, squ…
Reflection polarization of close binaries as a probe of axion dark matter birefringence
Tomoki Matsuoka, Kimihiro Nomura, Hidetoshi Omiya
We propose close binary polarimetry as a probe of birefringence induced by ultralight axion dark matter. In a close binary, reflection or scattering can generate a small linear pol…
Quantum Treatment of Black Hole Superradiance
Lingyun Fu, Hidetoshi Omiya, Takahiro Tanaka +3
Rotating black holes can form dense boson clouds through superradiant instability, making Kerr black holes a powerful probe of ultralight massive bosons. Previous studies of black…
Spectral instability of parametrized black hole quasinormal modes in the high-overtone limit via the exact WKB analysis
Taiga Miyachi, Ryo Namba, Hidetoshi Omiya +1
We study the asymptotic behavior of parametrized black hole quasinormal modes (QNMs) in the high-overtone limit. To gain insights into their analytical structure, we apply the exac…
Detecting Parity-Violating Gravitational Wave Backgrounds with Pulsar Polarization Arrays
Qiuyue Liang, Kimihiro Nomura, Hidetoshi Omiya
Pulsar timing arrays probe isotropic stochastic gravitational wave (GW) backgrounds in the nanohertz band but are insensitive to its parity-violating component. Motivated by recent…
Signature of polarized ultralight vector dark matter in pulsar timing arrays
Kimihiro Nomura, Hidetoshi Omiya, Takahiro Tanaka
We investigate observational signatures of ultralight vector dark matter with masses - eV in pulsar timing arrays, taking into account general polarizati…
Possibility of Multi-Messenger Observations of Quasi-Periodic Eruptions with X-rays and Gravitational Waves
Tomoya Suzuguchi, Hidetoshi Omiya, Hiroki Takeda
Recent X-ray observations have discovered a class of periodic X-ray flares in galactic nuclei known as quasi-periodic eruptions (QPEs). A promising explanation of QPEs is an emissi…
Resonant DM scattering in the galactic center under the influence of EMRI
Takafumi Kakehi, Hidetoshi Omiya, Takuya Takahashi +1
Dark matter (DM) search is one of the greatest challenges in physics. If DM consists of particles, it may form a spike around supermassive black holes (BH) prevalent in galaxy cent…
Path to an exact WKB analysis of black hole quasinormal modes
Taiga Miyachi, Ryo Namba, Hidetoshi Omiya +1
We investigate black hole quasinormal modes using the exact WKB method. We perform an analytic continuation from the horizon to infinity along the positive real axis of the radial…
Self-interacting axion clouds around rotating black holes in binary systems
Takuya Takahashi, Hidetoshi Omiya, Takahiro Tanaka
Superradiant instability can form clouds around rotating black holes (BHs) composed of ultralight bosonic fields, such as axions. A BH with such a cloud in a binary system exhibits…
Deci-Hz gravitational waves from the self-interacting axion cloud around the rotating stellar mass black hole
Hidetoshi Omiya, Takuya Takahashi, Takahiro Tanaka +1
Gravitational waves from condensates of ultra-light particles, such as axion, around rotating black holes are a promising probe to search for unknown physics. For this purpose, we…
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…
Scalar polarization window in gravitational-wave signals
Hiroki Takeda, Yusuke Manita, Hidetoshi Omiya +1
Scalar polarization modes of gravitational waves, which are often introduced in the context of the viable extension of gravity, have been actively searched. However, couplings of t…
Evolution of binary systems accompanying axion clouds in extreme mass ratio inspirals
Takuya Takahashi, Hidetoshi Omiya, Takahiro Tanaka
Superradiant instability of rotating black holes (BHs) leads to the formation of a cloud of ultralight bosons, such as axions. When the BH with the cloud belongs to a binary system…
Measuring the maximally allowed polarization states of the isotropic stochastic gravitational wave background with the ground-based detectors
Hidetoshi Omiya, Naoki Seto
We discuss the polarizational study of isotropic gravitational wave backgrounds with the second generation detector network, paying special attention to the impacts of adding LIGO-…
Impact of multiple modes on the evolution of self-interacting axion condensate around rotating black holes
Hidetoshi Omiya, Takuya Takahashi, Takahiro Tanaka +1
Ultra-light particles, such as axions, form a macroscopic condensate around a highly spinning black hole by the superradiant instability. Due to its macroscopic nature, the condens…
Adiabatic evolution of the self-interacting axion field around rotating black holes
Hidetoshi Omiya, Takuya Takahashi, Takahiro Tanaka
Ultra light axion fields, motivated by the string theory, form a large condensate (axion cloud) around rotating black holes through superradiant instability. Several effects due to…
Axion cloud evaporation during inspiral of black hole binaries -- the effects of backreaction and radiation
Takuya Takahashi, Hidetoshi Omiya, Takahiro Tanaka
Ultralight scalar fields such as axions can form clouds around rotating black holes (BHs) by the superradiant instability. It is important to consider the evolution of clouds assoc…
Correlation analysis for isotropic stochastic gravitational wave backgrounds with maximally allowed polarization degrees
Hidetoshi Omiya, Naoki Seto
We study correlation analysis for monopole components of stochastic gravitational wave backgrounds, including the maximally allowed polarization degrees. We show that, for typical…
Causal Structures and Nonlocality in Double Holography
Hidetoshi Omiya, Zixia Wei
Double holography plays a crucial role in recent studies of Hawking radiation and information paradox by relating an intermediate picture, in which a dynamical gravity living on an…
Renormalization group analysis of superradiant growth of self-interacting axion cloud
Hidetoshi Omiya, Takuya Takahashi, Takahiro Tanaka
There are strong interests in considering ultra-light scalar fields (especially axion) around a rapidly rotating black hole because of the possibility of observing gravitational wa…
Searching anomalous polarization modes of stochastic gravitational wave background with LISA and Taiji
Hidetoshi Omiya, Naoki Seto
The vector and scalar polarization modes of gravitational waves do not exist in General Relativity, and their detection would have significant impacts on fundamental physics. In th…