334 citations · 4k across the 75 of their papers we have counts for
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Stealth dark energy in scordatura DHOST theory
Mohammad Ali Gorji, Hayato Motohashi, Shinji Mukohyama
A stealth de Sitter solution in scalar-tensor theories has an exact de Sitter background metric and a nontrivial scalar field profile. Recently, in the context of Degenerate Higher…
On Rotating Black Holes in DHOST Theories
Jibril Ben Achour, Hongguang Liu, Hayato Motohashi +2
Using the disformal solution-generating method, we construct new axisymmetric solutions in Degenerate Higher Order Scalar Tensor (DHOST) theories. The method consists in first cons…
General Relativity solutions with stealth scalar hair in quadratic higher-order scalar-tensor theories
Kazufumi Takahashi, Hayato Motohashi
We explore General Relativity solutions with stealth scalar hair in general quadratic higher-order scalar-tensor theories. Adopting the assumption that the scalar field has a const…
Effective field theory of degenerate higher-order inflation
Hayato Motohashi, Wayne Hu
We extend the effective field theory of inflation to a general Lagrangian constructed from Arnowitt-Deser-Misner variables that encompasses the most general interactions with up to…
Quantum Ostrogradsky theorem
Hayato Motohashi, Teruaki Suyama
The Ostrogradsky theorem states that any classical Lagrangian that contains time derivatives higher than the first order and is nondegenerate with respect to the highest-order deri…