10 papers
Revisiting Coincident GR in Internal STEGR Formulation
Kyosuke Tomonari, Taishi Katsuragawa, Shin'ichi Nojiri
We revisit Coincident General Relativity (CGR) in the gauge approach to gravity based on Symmetric Teleparallel Equivalent to General Relativity (STEGR) in the \textit{internal-spa…
Technically Natural Suppression of Fifth Force
Kensuke Homma, Taishi Katsuragawa, Shinya Matsuzaki
Light scalars generically mediate a fifth force incompatible with local tests of gravity unless their couplings are parametrically suppressed or screening mechanisms are introduced…
Theoretical and observational constraints on early dark energy in gravity
Hua Chen, Taishi Katsuragawa, Shin'ichi Nojiri +1
This work examines an early dark energy (EDE) scenario in the context of gravity. EDE is introduced to alleviate the Hubble tension by temporarily injecting approximately $1…
Scalar-Induced Electromagnetic Radiation: Comparison with Axion-Like Particles and Implications for Modified Gravity
Wenyi Wang, Sousuke Noda, Taishi Katsuragawa
The scalar-tensor theory of gravity, a modified gravity theory, introduces a fundamental scalar field that can serve as dynamical dark energy, driving the late-time accelerated exp…
Cosmological Perturbation in New General Relativity: Propagating mode from the violation of local Lorentz invariance
Kyosuke Tomonari, Taishi Katsuragawa, Shin'ichi Nojiri
We investigate the propagating modes of New General Relativity (NGR) in second-order linear perturbations in the Lagrangian density (first-order in field equations). The Dirac-Berg…
Stimulated radiation from superradiant scalar cloud in scalar-tensor theory
Wenyi Wang, Sousuke Noda, Taishi Katsuragawa
Scalar-tensor theories predict fundamental scalar fields of considerable interest in astrophysics and cosmology. We investigate the superradiant instability of scalar clouds around…