The CMB temperature trispectrum of cosmic strings (2009)
Hindmarsh, Mark, Ringeval, Christophe, Suyama, Teruaki
We provide an analytical expression for the trispectrum of the Cosmic Microwave Background (CMB) temperature anisotropies induced by cosmic strings. Our result is derived for the small angular scales...
Cosmological perturbations of a perfect fluid and non-commutative geometry (2009)
De Felice, Antonio, Gerard, Jean-Marc, Suyama, Teruaki
We provide an action that describes the linear cosmological perturbations of a perfect fluid. This action is suited not only to perfect fluids with a barotropic equation of state, but also to those...
The CMB temperature bispectrum induced by cosmic strings (2009)
Hindmarsh, Mark, Ringeval, Christophe, Suyama, Teruaki
The Cosmic Microwave Background (CMB) bispectrum of the temperature anisotropies induced by a network of cosmic strings is derived for small angular scales, under the assumption that the principal...
Scalar mode propagation in modified gravity with a scalar field (2009)
De Felice, Antonio, Suyama, Teruaki
We study the propagation of the scalar modes around a Friedmann-Lemaitre-Robertson-Walker universe for general modifications of gravity in the presence of a real scalar field. In general, there will...
Vacuum structure for scalar cosmological perturbations in Modified Gravity Models (2009)
De Felice, Antonio, Suyama, Teruaki
We have found for the general class of Modified Gravity Models f(R,G) a new instability which can arise in vacuum for the scalar modes of the cosmological perturbations if the background is not de...
Yokoyama, Shuichiro, Suyama, Teruaki, Tanaka, Takahiro
We present a new efficient method for computing the non-linearity parameters of the higher order correlation functions of local type curvature perturbations in inflation models having a $\cal...
A General Analysis of Non-Gaussianity from Isocurvature Perturbations (2008)
Kawasaki, Masahiro, Nakayama, Kazunori, Sekiguchi, Toyokazu, Suyama, Teruaki, Takahashi, Fuminobu
Light scalars may be ubiquitous in nature, and their quantum fluctuations can produce large non-Gaussianity in the cosmic microwave background temperature anisotropy. The non-Gaussianity may be...
Non-Gaussianity from isocurvature perturbations (2008)
Kawasaki, Masahiro, Nakayama, Kazunori, Sekiguchi, Toyokazu, Suyama, Teruaki, Takahashi, Fuminobu
We develop a formalism to study non-Gaussianity in both curvature and isocurvature perturbations. It is shown that non-Gaussianity in the isocurvature perturbation between dark matter and photons...
Exact gravitational lensing by cosmic strings with junctions (2008)
We point out that the results by Brandenberger et al. in Phys.Rev.D77:083502(2008) that the geometry around the straight cosmic strings with stationary junctions is flat to linear order in the string...
Primordial Curvature Fluctuation and Its Non-Gaussianity in Models with Modulated Reheating (2008)
Ichikawa, Kazuhide, Suyama, Teruaki, Takahashi, Tomo, Yamaguchi, Masahide
We investigate non-Gaussianity in the modulated reheating scenario where fluctuations of the decay rate of the inflaton generate adiabatic perturbations, paying particular attention to the...
Non-Gaussianity from Symmetry (2008)
Suyama, Teruaki, Takahashi, Fuminobu
We point out that a light scalar field fluctuating around a symmetry-enhaced point can generate large non-Gaussianity in density fluctuations. We name such a particle as an "ungaussiton", a scalar...
Non-Gaussianity, Spectral Index and Tensor Modes in Mixed Inflaton and Curvaton Models (2008)
Ichikawa, Kazuhide, Suyama, Teruaki, Takahashi, Tomo, Yamaguchi, Masahide
We study non-Gaussianity, the spectral index of primordial scalar fluctuations and tensor modes in models where fluctuations from the inflaton and the curvaton can both contribute to the present...
Primordial Non-Gaussianity in Multi-Scalar Inflation (2007)
Yokoyama, Shuichiro, Suyama, Teruaki, Tanaka, Takahiro
We give a concise formula for the non-Gaussianity of the primordial curvature perturbation generated on super-horizon scales in multi-scalar inflation model without assuming slow-roll conditions....
Non-Gaussianity in the modulated reheating scenario (2007)
Suyama, Teruaki, Yamaguchi, Masahide
We investigate the non-Gaussianity of primordial curvature perturbation in the modulated reheating scenario where the primordial perturbation is generated due to the spacial fluctuation of the...
Primordial Non-Gaussianity in Multi-Scalar Slow-Roll Inflation (2007)
Yokoyama, Shuichiro, Suyama, Teruaki, Tanaka, Takahiro
We analyze the non-Gaussianity for primordial curvature perturbations generated in multi-scalar slow-roll inflation model including the model with non-separable potential by making use of $\delta N$...
Generating the primordial curvature perturbations in preheating (2006)
Suyama, Teruaki, Yokoyama, Shuichiro
We show that the primordial curvature perturbations may originate not from the quantum fluctuations of inflaton during inflation but from isocurvature perturbations which are amplified during...
Black hole production in tachyonic preheating (2006)
Suyama, Teruaki, Tanaka, Takahiro, Bassett, Bruce, Kudoh, Hideaki
We present fully non-linear simulations of a self-interacting scalar field in the early universe undergoing tachyonic preheating. We find that density perturbations on sub-horizon scales which are...
Exact Wave Propagation in a Spacetime with a Cosmic String (2005)
Suyama, Teruaki, Tanaka, Takahiro, Takahashi, Ryuichi
We present exact solutions of the massless Klein-Gordon equation in a spacetime in which an infinite straight cosmic string resides. The first solution represents a plane wave entering perpendicular...
Suyama, Teruaki, Takahashi, Ryuichi, Michikoshi, Shugo
Wave effects can be important for the gravitational lensing of gravitational waves. In such a case, wave optics must be used in stead of geometric optics. We consider a plane wave entering a lens...
Scattering of Gravitational Waves by the Weak Gravitational Fields of Lens Objects (2005)
Takahashi, Ryuichi, Suyama, Teruaki, Michikoshi, Shugo
We consider the scattering of the gravitational waves by the weak gravitational fields of lens objects. We obtain the scattered gravitational waveform by treating the gravitational potential of the...
Are black holes over-produced during preheating? (2004)
Suyama, Teruaki, Tanaka, Takahiro, Bassett, Bruce, Kudoh, Hideaki
We provide a simple but robust argument that primordial black hole (PBH) production generically does {\em not} exceed astrophysical bounds during the resonant preheating phase after inflation. This...