4 papers
Unscreened multipole moments of the fifth force in the EFT of dark energy
Tsutomu Kobayashi, Toshiki Takadera
It has been argued that degenerate higher-order scalar-tensor theories and the effective field theory (EFT) of dark energy are endowed with the Vainshtein mechanism, resulting in a…
Abundance of cosmic voids in EFT of dark energy
Toshiki Takadera, Shin'ichi Hirano, Tsutomu Kobayashi
Cosmic voids in the large-scale structure are among the useful probes for testing gravity on cosmological scales. In this paper, we investigate the evolution of voids in the Hornde…
Spherical collapse in DHOST theories and EFT of dark energy
Toshiki Takadera, Takashi Hiramatsu, Tsutomu Kobayashi
We study the nonlinear evolution of matter overdensities using the spherical collapse model in degenerate higher-order scalar-tensor (DHOST) theories beyond Horndeski, employing th…
Weak-field regime of scalar-tensor theories with an instantaneous mode
Tsutomu Kobayashi, Takashi Hiramatsu
Higher-order scalar-tensor theories having an instantaneous mode do not develop the Ostrogradsky instability even if a seemingly dangerous mode is present. Such theories satisfy on…