Publications (34)
Non-relativistic stellar structure in higher-curvature gravity: systematic construction of solutions to the modified Lane-Emden equations
Shinpei Tonosaki, Tomoya Tachinami, Yuuiti Sendouda
We study the structure of static spherical stars made up of a non-relativistic polytropic fluid in linearized higher-curvature theories of gravity (HCG). We first formulate the mod…
Rapid Merger of Binary Primordial Black Holes: an Implication for GW150914
Kimitake Hayasaki, Keitaro Takahashi, Yuuiti Sendouda +1
We propose a new scenario for the evolution of a binary of primordial black holes (PBHs). We consider a dynamical friction by ambient dark matter, scattering of dark matter particl…
Analytical model for CMB temperature angular power spectrum from cosmic (super-)strings
Daisuke Yamauchi, Keitaro Takahashi, Yuuiti Sendouda +2
We present a new analytical method to calculate the small angle CMB temperature angular power spectrum due to cosmic (super-)string segments. In particular, using our method, we cl…
Instability of de Sitter brane and horizon entropy in a 6D braneworld
Shunichiro Kinoshita, Yuuiti Sendouda, Shinji Mukohyama
We investigate thermodynamic and dynamical stability of a family of six-dimensional braneworld solutions with de Sitter branes. First, we investigate thermodynamic stability in ter…
"Detuned" f(R) gravity and dark energy
Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda
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 fie…
Lorentz-violating vs ghost gravitons: the example of Weyl gravity
Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda +1
We show that the ghost degrees of freedom of Einstein gravity with a Weyl term can be eliminated by a simple mechanism that invokes local Lorentz symmetry breaking. We demonstrate…
Various Hamiltonian formulations of f(R) gravity and their canonical relationships
Nathalie Deruelle, Yuuiti Sendouda, Ahmed Youssef
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…
A quantisation procedure in the presence of an initial Kasner singularity: primordial gravitational waves from triaxially anisotropic pre-inflation
Yu Furuya, Yuki Niiyama, Yuuiti Sendouda
In this paper, we discuss quantisation of cosmological tensor perturbations in the Kasner-de Sitter space-time as a model of (pre-)inflation. Quantisation in such an anisotropic ba…
Non-Gaussianity in Cosmic Microwave Background Temperature Fluctuations from Cosmic (Super-)Strings
Keitaro Takahashi, Atsushi Naruko, Yuuiti Sendouda +3
We compute analytically the small-scale temperature fluctuations of the cosmic microwave background from cosmic (super-)strings and study the dependence on the string intercommutin…
Dynamical Stability of Six-dimensional Warped Flux Compactification
Hiroyuki Yoshiguchi, Shinji Mukohyama, Yuuiti Sendouda +1
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 th…
Constraints on primordial black holes from Galactic gamma-ray background
B. J. Carr, Kazunori Kohri, Yuuiti Sendouda +1
The fraction of the Universe going into primordial black holes (PBHs) with initial mass M_* \approx 5 \times 10^{14} g, such that they are evaporating at the present epoch, is stro…
New cosmological constraints on primordial black holes
B. J. Carr, Kazunori Kohri, Yuuiti Sendouda +1
We update the constraints on the fraction of the Universe going into primordial black holes in the mass range 10^9--10^17 g associated with the effects of their evaporations on big…
Femto-lensing due to a Cosmic String
Chul-Moon Yoo, Ryo Saito, Yuuiti Sendouda +2
We consider the femto-lensing due to a cosmic string. If a cosmic string with the deficit angle [femto-arcsec] [rad] exists around the line of sight to…
Quadrupole formula for Kaluza-Klein modes in the braneworld
Shunichiro Kinoshita, Hideaki Kudoh, Yuuiti Sendouda +1
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) mo…
A doubly covariant formula of deficit angle and its application to six-dimensional braneworld
Yuuiti Sendouda, Shunichiro Kinoshita, Shinji Mukohyama
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…
Non-Fierz-Pauli bimetric theory from quadratic curvature gravity on Einstein manifolds
Yuki Niiyama, Yuya Nakamura, Ryosuke Zaimokuya +2
We show that, in four-dimensional spacetimes with an arbitrary Einstein metric, with and without a cosmological constant, perturbative dynamical degrees of freedom in generic quadr…
CMB ISW-lensing bispectrum from cosmic strings
Daisuke Yamauchi, Yuuiti Sendouda, Keitaro Takahashi
We study the effect of weak lensing by cosmic (super-)strings on the higher-order statistics of the cosmic microwave background (CMB). A cosmic string segment is expected to cause…
Sub-GeV galactic cosmic-ray antiprotons from primordial black holes in the Randall-Sundrum braneworld
Yuuiti Sendouda, Kazunori Kohri, Shigehiro Nagataki +1
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 observati…
Hamiltonian formulation of f(Riemann) theories of gravity
Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda +1
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…
Constraints on the mass spectrum of primordial black holes and braneworld parameters from the high-energy diffuse photon background
Yuuiti Sendouda, Shigehiro Nagataki, Katsuhiko Sato
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 bra…
Constraints on Primordial Black Holes
Bernard Carr, Kazunori Kohri, Yuuiti Sendouda +1
We update the constraints on the fraction of the Universe that may have gone into primordial black holes (PBHs) over the mass range g. Those smaller than…
Junction Conditions in f(R) Theories of Gravity
Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda
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 cl…
Gravitational-wave polarizations in generic linear massive gravity and generic higher-curvature gravity
Tomoya Tachinami, Shinpei Tonosaki, Yuuiti Sendouda
We study the polarizations of gravitational waves (GWs) in two classes of extended gravity theories. First, we formulate the polarizations in linear massive gravity (MG) with gener…
Observable induced gravitational waves from an early matter phase
Laila Alabidi, Kazunori Kohri, Misao Sasaki +1
Assuming that inflation is succeeded by a phase of matter domination, which corresponds to a low temperature of reheating , we evaluate the spectra of gravitation…
Observable Spectra of Induced Gravitational Waves from Inflation
Laila Alabidi, Kazunori Kohri, Misao Sasaki +1
Measuring the primordial power spectrum on small scales is a powerful tool in inflation model building, yet constraints from Cosmic Microwave Background measurements alone are insu…
Weak lensing of CMB by cosmic (super-)strings
Daisuke Yamauchi, Keitaro Takahashi, Yuuiti Sendouda +1
We study the effect of weak lensing by cosmic (super-)strings on the anisotropies of cosmic microwave background (CMB). In developing a method to calculate the lensing convergence…
Non-relativistic stellar structure in the Fierz--Pauli theory and generic linear massive gravity
Tomoya Tachinami, Yuuiti Sendouda
We study the structure of static spherical stars composed of non-relativistic matter in linear massive gravity with or without the Fierz-Pauli (FP) tuning. Adopting a polytropic eq…
Skewness in CMB temperature fluctuations from curved cosmic (super-)strings
Daisuke Yamauchi, Yuuiti Sendouda, Chul-Moon Yoo +3
We compute the one-point probability distribution function of small-angle cosmic microwave background temperature fluctuations due to curved cosmic (super-)strings with a simple mo…
Type-I cosmic string network
Takashi Hiramatsu, Yuuiti Sendouda, Keitaro Takahashi +2
We study the network of Type-I cosmic strings using the field-theoretic numerical simulations in the Abelian-Higgs model. For Type-I strings, the gauge field plays an important rol…
Acoustic causality in relativistic shells
Shunichiro Kinoshita, Yuuiti Sendouda, Keitaro Takahashi
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 effec…
Inflation with a Weyl term, or ghosts at work
Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda +1
In order to assess the role of ghosts in cosmology, we study the evolution of linear cosmological perturbations during inflation when a Weyl term is added to the action. Our main r…
Warped Flux Compactification and Brane Gravity
Shinji Mukohyama, Yuuiti Sendouda, Hiroyuki Yoshiguchi +1
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…
Probing pre-inflationary anisotropy with directional variations in the gravitational wave background
Yu Furuya, Yuki Niiyama, Yuuiti Sendouda
We perform a detailed analysis on a primordial gravitational-wave background amplified during a Kasner-like pre-inflationary phase allowing for general triaxial anisotropies. It is…
Mass spectrum of primordial black holes from inflationary perturbation in the Randall-Sundrum braneworld: a limit on blue spectra
Yuuiti Sendouda, Shigehiro Nagataki, Katsuhiko Sato
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 coincid…