423 citations · 1.8k across the 30 of their papers we have counts for
9 papers · 1 filter
Ostrogradsky mode in scalar-tensor theories with higher-order derivative couplings to matter
Atsushi Naruko, Ryo Saito, Norihiro Tanahashi +1
A metric transformation is a tool to find a new theory of gravity beyond general relativity. The gravity action is guaranteed to be free from a dangerous Ostrogradsky mode as long…
Antipodal Angular Correlations of Inflationary Stochastic Gravitational Wave Background
Zhen-Yuan Wu, Ryo Saito, Nobuyuki Sakai
The measurement of the inflationary stochastic gravitational-wave background (SGWB) is one of the main goals of future GW experiments. In direct GW experiments, an obstacle to achi…
Dynamical Analysis of Screening in Scalar-Tensor Theory
Tomohiro Nakamura, Taishi Ikeda, Ryo Saito +2
We investigate linear and non-linear dynamics of spherically symmetric perturbations on a static configuration in scalar-tensor theories focusing on the chameleon screening mechani…
Chameleon Field in a Spherical Shell System
Tomohiro Nakamura, Taishi Ikeda, Ryo Saito +1
We investigate the validity of screening mechanism of the fifth force for chameleon field in highly inhomogeneous density profile. For simplicity, we consider a static and spherica…
Scalar-tensor theories and modified gravity in the wake of GW170817
David Langlois, Ryo Saito, Daisuke Yamauchi +1
Theories of dark energy and modified gravity can be strongly constrained by astrophysical or cosmological observations, as illustrated by the recent observation of the gravitationa…
Towards Strong Field Tests of Beyond Horndeski Gravity Theories
Jeremy Sakstein, Eugeny Babichev, Kazuya Koyama +2
Theories of gravity in the beyond Horndeski class encompass a wide range of scalar-tensor theories that will be tested on cosmological scales over the coming decade. In this work,…
Relativistic Stars in Beyond Horndeski Theories
Eugeny Babichev, Kazuya Koyama, David Langlois +2
This work studies relativistic stars in beyond Horndeski scalar-tensor theories that exhibit a breaking of the Vainshtein mechanism inside matter, focusing on a model based on the…
Beyond Fab Four
E. Babichev, C. Charmousis, D. Langlois +1
We show that the two additional Lagrangians that appear in theories beyond Horndeski can be reexpressed in terms of simple generalizations of the "John" and "Paul" terms of the Fab…
Modified gravity inside astrophysical bodies
Ryo Saito, Daisuke Yamauchi, Shuntaro Mizuno +2
Many theories of modified gravity, including the well studied Horndeski models, are characterized by a screening mechanism that ensures that standard gravity is recovered near astr…