96 citations · 1.2k across the 37 of their papers we have counts for
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Invertible disformal transformations with higher derivatives
Kazufumi Takahashi, Hayato Motohashi, Masato Minamitsuji
We consider a higher-derivative generalization of disformal transformations in -dimensional spacetime and clarify the conditions under which they form a group with respect to th…
The Effective Field Theory of Vector-Tensor Theories
Katsuki Aoki, Mohammad Ali Gorji, Shinji Mukohyama +1
We investigate a systematic formulation of vector-tensor theories based on the effective field theory (EFT) approach. The input of our EFT is that the spacetime symmetry is spontan…
Nonlinear definition of the shadowy mode in higher-order scalar-tensor theories
Antonio De Felice, Shinji Mukohyama, Kazufumi Takahashi
We study U-DHOST theories, i.e., higher-order scalar-tensor theories which are degenerate only in the unitary gauge and yield an apparently unstable extra mode in a generic coordin…
Cosmic No-hair Conjecture and Inflation with an SU(3) Gauge Field
Pengyuan Gao, Kazufumi Takahashi, Asuka Ito +1
We study inflationary universes with an SU(3) gauge field coupled to an inflaton through a gauge kinetic function. Although the SU(3) gauge field grows at the initial stage of infl…
Black hole perturbations in DHOST theories: Master variables, gradient instability, and strong coupling
Kazufumi Takahashi, Hayato Motohashi
We study linear perturbations about static and spherically symmetric black hole solutions with stealth scalar hair in degenerate higher-order scalar-tensor (DHOST) theories. We cla…