32 citations · 50 across the 3 of their papers we have counts for
7 papers
Effective Field Theory of Large Scale Structure in modified gravity and application to Degenerate Higher-Order Scalar-Tensor theories
Shin'ichi Hirano, Tomohiro Fujita
In modified gravity, the one-loop matter power spectrum exhibits an ultraviolet divergence as shown in the framework of the degenerate higher-order scalar-tensor theory. To address…
Gravitational positivity bounds
Junsei Tokuda, Katsuki Aoki, Shin'ichi Hirano
We study the validity of positivity bounds in the presence of a massless graviton, assuming the Regge behavior of the amplitude. Under this assumption, the problematic -channel…
UV sensitive one-loop matter power spectrum in degenerate higher-order scalar-tensor theories
Shin'ichi Hirano, Tsutomu Kobayashi, Daisuke Yamauchi +1
We study matter density perturbations up to third order and the one-loop matter power spectrum in degenerate higher-order scalar-tensor (DHOST) theories beyond Horndeski. We system…
Primordial tensor non-Gaussianities from general single-field inflation with non-Bunch-Davies initial states
Shingo Akama, Shin'ichi Hirano, Tsutomu Kobayashi
It has been found that the primordial non-Gaussianity of the curvature perturbation in the case of non-Bunch-Davies initial states can be enhanced compared with those in the case o…
Primordial non-Gaussianities of scalar and tensor perturbations in general bounce cosmology: Evading the no-go theorem
Shingo Akama, Shin'ichi Hirano, Tsutomu Kobayashi
It has been pointed out that matter bounce cosmology driven by a k-essence field cannot satisfy simultaneously the observational bounds on the tensor-to-scalar ratio and non-Gaussi…
On the screening mechanism in DHOST theories evading gravitational wave constraints
Shin'ichi Hirano, Tsutomu Kobayashi, Daisuke Yamauchi
We consider a subclass of degenerate higher-order scalar-tensor (DHOST) theories in which gravitational waves propagate at the speed of light and do not decay into scalar fluctuati…