54 citations · 159 across the 5 of their papers we have counts for
5 papers
Self-anisotropizing inflationary universe in Horndeski theory and beyond
Hiroaki W. H. Tahara, Sakine Nishi, Tsutomu Kobayashi +1
As opposed to Wald's cosmic no-hair theorem in general relativity, it is shown that the Horndeski theory (and its generalization) admits anisotropic inflationary attractors if the…
Healthy imperfect dark matter from effective theory of mimetic cosmological perturbations
Shin'ichi Hirano, Sakine Nishi, Tsutomu Kobayashi
We study the stability of a recently proposed model of scalar-field matter called mimetic dark matter or imperfect dark matter. It has been known that mimetic matter with higher de…
Scale-invariant perturbations from NEC violation: A new variant of Galilean Genesis
Sakine Nishi, Tsutomu Kobayashi
We propose a novel branch of the Galilean Genesis scenario as an alternative to inflation, in which the universe starts expanding from Minkowski in the asymptotic past with a gross…
Generalized Galilean Genesis
Sakine Nishi, Tsutomu Kobayashi
The galilean genesis scenario is an alternative to inflation in which the universe starts expanding from Minkowski in the asymptotic past by violating the null energy condition sta…
Cosmological matching conditions and galilean genesis in Horndeski's theory
Sakine Nishi, Tsutomu Kobayashi, Norihiro Tanahashi +1
We derive the cosmological matching conditions for the homogeneous and isotropic background and for linear perturbations in Horndeski's most general second-order scalar-tensor theo…