162 citations · 518 across the 6 of their papers we have counts for
11 papers
On the full quantum trispectrum in multi-field DBI inflation
Shuntaro Mizuno, Frederico Arroja, Kazuya Koyama
We compute the leading order connected four-point function of the primordial curvature perturbation coming from the four-point function of the fields in multi-field DBI inflation m…
Lorentz boost and non-Gaussianity in multi-field DBI-inflation
Shuntaro Mizuno, Frederico Arroja, Kazuya Koyama +1
We show that higher-order actions for cosmological perturbations in the multi-field DBI-inflation model are obtained by a Lorentz boost from the rest frame of the brane to the fram…
Dynamics of a scalar field in Robertson-Walker spacetimes
Edmund J. Copeland, Shuntaro Mizuno, Maryam Shaeri
We analyze the dynamics of a single scalar field in Friedmann-Robertson-Walker universes with spatial curvature. We obtain the fixed point solutions which are shown to be late time…
Constraints on scalar-tensor models of dark energy from observational and local gravity tests
Shinji Tsujikawa, Kotub Uddin, Shuntaro Mizuno +2
We construct a family of viable scalar-tensor models of dark energy (DE) which possess a phase of late-time acceleration preceded by a standard matter era, while at the same time s…
Non-Gaussianities from ekpyrotic collapse with multiple fields
Kazuya Koyama, Shuntaro Mizuno, Filippo Vernizzi +1
We compute the non-Gaussianity of the curvature perturbation generated by ekpyrotic collapse with multiple fields. The transition from the multi-field scaling solution to a single-…
Curvature perturbations from ekpyrotic collapse with multiple fields
Kazuya Koyama, Shuntaro Mizuno, David Wands
A scale-invariant spectrum of isocurvature perturbations is generated during collapse in the ekpyrotic scaling solution in models where multiple fields have steep negative exponent…