133 citations · 143 across the 7 of their papers we have counts for
7 papers
Bi-scalar-tensor theory: a spatially covariant gravity approach
Jia-Jun Chen, Xian Gao, Tsutomu Kobayashi
We propose a novel method for constructing ghost-free multi-field higher-derivative scalar-tensor theories. The idea is to start from spatially covariant gravity and couple it to a…
Healthy scalar-tensor theories with third-order derivatives: Generalized disformal Horndeski and beyond
Masaki Michiwaki, Tsutomu Kobayashi
We systematically construct a broad class of ghost-free scalar-tensor theories whose Lagrangian includes up to third-order derivatives of the scalar field. Using a spatially covari…
Gravitomagnetic tidal response of relativistic stars in partially screened scalar-tensor theories
Tsutomu Kobayashi
In scalar-tensor theories beyond Horndeski, the Vainshtein screening mechanism is only partially effective inside astrophysical bodies. We investigate the potential to detect this…
Slowly moving black holes in Lorentz-violating scalar-tensor gravity
Jin Saito, Tsutomu Kobayashi
A scalar field with a timelike gradient defines a preferred slicing. This occurs even in a non-cosmological setup in scalar-tensor theories such as khronometric theory. We study a…
Chromo-natural inflation supported by enhanced friction from Horndeski gravity
Tomoaki Murata, Tsutomu Kobayashi
We study the extension of the chromo-natural inflation model by incorporating nonminimal coupling between the axion field and gravity. Nonminimal coupling is introduced so that it…
PPN meets EFT of dark energy: Post-Newtonian approximation in higher-order scalar-tensor theories
Jin Saito, Zhibang Yao, Tsutomu Kobayashi
We study the post-Newtonian limit of higher-order scalar-tensor theories that are degenerate in the unitary gauge. They can be conveniently described by the effective field theory…
Effective scalar-tensor description of regularized Lovelock gravity in four dimensions
Tsutomu Kobayashi
We reformulate the recently proposed regularized version of Lovelock gravity in four dimensions as a scalar-tensor theory. By promoting the warp factor of the internal space to a s…