Large scale evolution of the curvature perturbation in Horava-Lifshitz cosmology (2009)
Kobayashi, Tsutomu, Urakawa, Yuko, Yamaguchi, Masahide
In the non-relativistic theory of gravity recently proposed by Horava, the Hamiltonian constraint is not satisfied locally at each point in space. The absence of the local Hamiltonian constraint...
A note on observational signatures in superluminal unified dark matter models (2009)
Urakawa, Yuko, Kobayashi, Tsutomu
We explore the possibility that the dark matter and dark energy are mimicked by a single fluid or by a single $k$-essence-like scalar field. The so called Chaplygin gas unified dark matter models can...
Influence on observation from IR divergence during inflation -- Multi field inflation -- (2009)
Urakawa, Yuko, Tanaka, Takahiro
We propose one way to regularize the fluctuations generated during inflation, whose infrared (IR) corrections diverge logarithmically. In the case of a single field inflation model, recently, we...
Influence on observation from IR divergence during inflation -- Single field inflation -- (2009)
Urakawa, Yuko, Tanaka, Takahiro
A naive computation of the correlation functions of fluctuations generated during inflation suffers from logarithmic divergences in the infrared (IR) limit. In this paper, we propose one way to solve...
Urakawa, Yuko, Maeda, Kei-ichi
Based on the stochastic gravity, we study the loop corrections to the scalar and tensor perturbations during inflation. Since the loop corrections to scalar perturbations suffer infrared (IR)...
Cosmological Density Fluctuations in Stochastic Gravity -- Formalism and Linear Analysis -- (2007)
Urakawa, Yuko, Maeda, Kei-ichi
We study primordial perturbations generated from quantum fluctuations of an inflaton based on the formalism of stochastic gravity. Integrating out the degree of freedom of the inflaton field, we...