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Determining the Equation of State of the Expanding Universe: Inverse Problem in Cosmology
Takashi Nakamura, Takeshi Chiba
Even if the luminosity distance as a function of redshift is obtained accurately using, for example, Type Ia supernovae, the equation of state of the Universe cannot be determined…
Low frequency gravitational waves from black hole MACHO binaries
Kunihito Ioka, Takahiro Tanaka, Takashi Nakamura
The intensity of low frequency gravitational waves from black hole MACHO binaries is studied. First we estimate the gravitational wave background produced by black hole MACHO binar…
The Luminosity Distance, the Equation of State, and the Geometry of the Universe
Takeshi Chiba, Takashi Nakamura
The second derivative of the luminosity distance with respect to the redshift is written in terms of the deceleration parameter . We point out that the third derivative contai…
Black Hole Binary Formation in the Expanding Universe --- Three Body Problem Approximation ---
Kunihito Ioka, Takeshi Chiba, Takahiro Tanaka +1
We study black hole MACHO binary formation through three-body interactions in the early universe at s. The probability distribution functions of the eccentricity and…
Observational tests of x-matter models
Takeshi Chiba, Naoshi Sugiyama, Takashi Nakamura
We study gravitational lensing statistics, matter power spectra and the angular power spectra of the cosmic microwave background (CMB) radiation in x-matter models. We adopt an equ…
Expected EAGLE event rate towards the Magellanic Clouds
Takashi Nakamura, Ryoichi Nishi
We propose to search for MACHOs by observing EAGLE (Extremely Amplified Gravitational LEnsing) events of a majority of dim stars. This search is independent of the usual one. For t…
Location of the innermost stable circular orbit of binary neutron stars in the post Newtonian approximations of general relativity
Masaru Shibata, Keisuke Taniguchi, Takashi Nakamura
In this paper, we present results obtained from our recent studies on the location of the innermost stable circular orbit (ISCO) for binary neutron stars (BNSs) in several levels o…