6 papers
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…
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…
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…
Remarks on overestimating the effects of inhomogeneities on the Hubble constant
Taishi Miura, Takahiro Tanaka
The Hubble constant is one of the most important parameters in cosmology. Discrepancies in values of the Hubble constant estimated from various measurements, the so-called Hubble t…
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…
Extending Hamiltonian Formulation of Particle Motion in Perturbed Kerr Spacetime to various time parameterizations
Takafumi Kakehi, Takahiro Tanaka
The Hamiltonian formulation with action-angle variables is very useful when considering the motion of particles undergoing a self-force reaction due to gravitational wave emission.…