2.4k citations · 6.1k across the 29 of their papers we have counts for
5 papers · 1 filter
Pathological behaviour of the scalar graviton in Hořava-Lifshitz gravity
Kazuya Koyama, Frederico Arroja
We confirm the recent claims that, in the infrared limit of Hořava-Lifshitz gravity, the scalar graviton becomes a ghost if the sound speed squared is positive on the flat de Sitte…
Cosmological matching conditions for gravitational waves at second order
Frederico Arroja, Hooshyar Assadullahi, Kazuya Koyama +1
We compute the second-order matching conditions for tensor metric perturbations at an abrupt change in the equation of state. For adiabatic perturbations on large scales the matchi…
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…
On the full trispectrum in single field DBI-inflation
Frederico Arroja, Shuntaro Mizuno, Kazuya Koyama +1
We compute the tree-level connected four-point function of the primordial curvature perturbation for a fairly general minimally coupled single field inflationary model, where the i…
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…