2 papers
astro-ph.CO2025
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…
gr-qc2023
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…