3 papers
gr-qc2025
Spherical black hole perturbations in EFT of scalar-tensor gravity with timelike scalar profile
Shinji Mukohyama, Kazufumi Takahashi, Keitaro Tomikawa +1
We study linear even-parity perturbations of static and spherically symmetric black holes with a timelike scalar profile by use of the effective field theory (EFT) approach. For il…
gr-qc2021
Perturbations and quasi-normal modes of black holes with time-dependent scalar hair in shift-symmetric scalar-tensor theories
Keitaro Tomikawa, Tsutomu Kobayashi
We study odd parity perturbations of spherically symmetric black holes with time-dependent scalar hair in shift-symmetric higher-order scalar-tensor theories. The analysis is perfo…
gr-qc2019
On the gauge dependence of gravitational waves generated at second order from scalar perturbations
Keitaro Tomikawa, Tsutomu Kobayashi
We revisit and clarify the gauge dependence of gravitational waves generated at second order from scalar perturbations. In a universe dominated by a perfect fluid with a constant e…