109 citations · 613 across the 27 of their papers we have counts for
10 papers · 1 filter
String Excitation by Initial Singularity of Inflation
Kanji Nishii, Daisuke Yoshida
We discuss excitation of string oscillation modes by an initial singularity of inflation. The initial singularity of inflation is known to occur with a finite Hubble parameter, whi…
invariant Fierz-Pauli massive gravity
Toshifumi Noumi, Kaishu Saito, Jiro Soda +1
We consider an invariant massive deformation of double field theory at the level of free theory. We study Kaluza-Klein reduction on and…
Birth of de Sitter Universe from time crystal
Daisuke Yoshida, Jiro Soda
We show that a simple sub-class of Horndeski theory can describe a time crystal Universe. The time crystal Universe can be regarded as a baby Universe nucleated from a flat space,…
2-form gauge theory dual to scalar-tensor theory
Daisuke Yoshida
We generalize the electromagnetic duality between a massless, canonical scalar field and a 2-form gauge field in 4-dimensional spacetime to scalar-tensor theories. We derive the ac…
Global Spacetime Structure of Compactified Inflationary Universe
Tokiro Numasawa, Daisuke Yoshida
We investigate the global spacetime structure of torus de Sitter universe, which is exact de Sitter space with torus identification based on the flat chart. We show that past incom…
Higher derivative scalar-tensor theory through a non-dynamical scalar field
Xian Gao, Masahide Yamaguchi, Daisuke Yoshida
We propose a new class of higher derivative scalar-tensor theories without the Ostrogradsky's ghost instabilities. The construction of our theory is originally motivated by a scala…
Pole inflation in Jordan frame supergravity
Ken'ichi Saikawa, Masahide Yamaguchi, Yasuho Yamashita +1
We investigate inflation models in Jordan frame supergravity, in which an inflaton non-minimally couples to the scalar curvature. By imposing the condition that an inflaton would h…
Cosmological perturbations and stability of nonsingular cosmologies with limiting curvature
Daisuke Yoshida, Jerome Quintin, Masahide Yamaguchi +1
We revisit nonsingular cosmologies in which the limiting curvature hypothesis is realized. We study the cosmological perturbations of the theory and determine the general criteria…
Coupling between Galileon and massive gravity with composite metrics
Xian Gao, Daisuke Yoshida
We investigate the coupling between a Galileon scalar field and massive gravity through composite metrics. We derive the full set of equations of motion for a flat Friedmann-Robert…
New Cosmological Solutions in Massive Gravity
Tsutomu Kobayashi, Masaru Siino, Masahide Yamaguchi +1
We find new, simple cosmological solutions with flat, open, and closed spatial geometries, contrary to the previous wisdom that only the open model is allowed. The metric and the S…