Rapid Merger of Binary Primordial Black Holes (2009)
Hayasaki, Kimitake, Takahashi, Keitaro, Sendouda, Yuuiti, Nagataki, Shigehiro
We propose a new scenario for the evolution of a binary of primordial black holes (PBHs). We consider the dynamical friction by ambient dark matter and gravitational interaction between a binary and...
Hamiltonian formulation of f(Riemann) theories of gravity (2009)
Deruelle, Nathalie, Sasaki, Misao, Sendouda, Yuuiti, Yamauchi, Daisuke
We present a canonical formulation of gravity theories whose Lagrangian is an arbitrary function of the Riemann tensor. Our approach allows a unified treatment of various subcases and an easy...
Various Hamiltonian formulations of f(R) gravity and their canonical relationships (2009)
Deruelle, Nathalie, Sendouda, Yuuiti, Youssef, Ahmed
Various Hamiltonian formulations of f(R) gravity can be found in the literature. Some authors follow the Ostrogradsky treatment of higher derivative theories and introduce as extra variables first...
Takahashi, Keitaro, Naruko, Atsushi, Sendouda, Yuuiti, Yamauchi, Daisuke, Yoo, Chul-Moon, Sasaki, Misao
We compute analytically the small-scale temperature fluctuations of cosmic microwave background from cosmic (super-)strings and study the dependence on the string intercommuting probability $P$. We...
"Detuned" f(R) gravity and dark energy (2008)
Deruelle, Nathalie, Sasaki, Misao, Sendouda, Yuuiti
In gravity theories derived from a f(R) Lagrangian, matter is usually supposed to be minimally coupled to the metric, which hence defines a ``Jordan frame.'' However, since the field equations are...
Junction Conditions in f(R) Theories of Gravity (2007)
Deruelle, Nathalie, Sasaki, Misao, Sendouda, Yuuiti
Taking advantage of the conformal equivalence of f(R) theories of gravity with General Relativity coupled to a scalar field we generalize the Israel junction conditions for this class of theories by...
Instability of de Sitter brane and horizon entropy in a 6D braneworld (2007)
Kinoshita, Shunichiro, Sendouda, Yuuiti, Mukohyama, Shinji
We investigate thermodynamic and dynamical stability of a family of six-dimensional braneworld solutions with de Sitter branes. First, we investigate thermodynamic stability in terms of de Sitter...
A doubly covariant formula of deficit angle and its application to six-dimensional braneworld (2006)
Sendouda, Yuuiti, Kinoshita, Shunichiro, Mukohyama, Shinji
We reformulate boundary conditions for axisymmetric codimension-2 braneworlds in a way which is applicable to linear perturbation with various gauge conditions. Our interest is in the thin brane...
Sendouda, Yuuiti, Nagataki, Shigehiro, Sato, Katsuhiko
The mass spectrum of the primordial black holes formed by density perturbation in the radiation-dominated era of the Randall-Sundrum type-2 cosmology is given. The spectrum coincides with standard...
Dynamical Stability of Six-dimensional Warped Flux Compactification (2005)
Yoshiguchi, Hiroyuki, Mukohyama, Shinji, Sendouda, Yuuiti, Kinoshita, Shunichiro
We show the dynamical stability of a six-dimensional braneworld solution with warped flux compactification recently found by the authors. We consider linear perturbations around this background...
Warped Flux Compactification and Brane Gravity (2005)
Mukohyama, Shinji, Sendouda, Yuuiti, Yoshiguchi, Hiroyuki, Kinoshita, Shunichiro
We find a simple exact solution of 6-dimensional braneworld which captures some essential features of warped flux compactification, including a warped geometry, compactification, a magnetic flux, and...
Quadrupole formula for Kaluza-Klein modes in the braneworld (2005)
Kinoshita, Shunichiro, Kudoh, Hideaki, Sendouda, Yuuiti, Sato, Katsuhiko
The quadrupole formula in four-dimensional Einstein gravity is a useful tool to describe gravitational wave radiation. We derive the quadrupole formula for the Kaluza-Klein (KK) modes in the...
Sendouda, Yuuiti, Kohri, Kazunori, Nagataki, Shigehiro, Sato, Katsuhiko
We investigate cosmic-ray antiprotons emitted from the galactic primordial black holes in the Randall-Sundrum type-2 braneworld. The recent results of the BESS antiproton observation implies the...
Acoustic causality in relativistic shells (2004)
Kinoshita, Shunichiro, Sendouda, Yuuiti, Takahashi, Keitaro
The motion of sound waves propagating in the perfect fluid with inhomogeneous background flow is effectively described as a massless scalar field on a curved space-time. This effective geometry is...
Sendouda, Yuuiti, Nagataki, Shigehiro, Sato, Katsuhiko
We investigate the spectral shape of a high-energy diffuse photon emitted by evaporating primordial black holes (PBHs) in the Randall-Sundrum type II (RS2) braneworld. In their braneworld scenario,...