Miura, Takaho, Arakida, Hideyoshi, Kasai, Masumi, Kuramata, Shuichi
We give an idea and the order-of-magnitude estimations to explain the recently reported secular increase of the Astronomical Unit (AU) by Krasinsky and Brumberg (2004). The idea proposed is analogous...
We re-analyze the observed magnitude-redshift relation of type Ia supernovae (SNe Ia) and examine the possibility that the apparent acceleration of the cosmic expansion is not caused by dark energy...
Konno, Kohkichi, Kasai, Masumi
We present a general relativistic framework for studying gravitational effects in quantum mechanical phenomena. We concentrate our attention on the case of ultra-relativistic, spin-1/2 particles...
Toward a No-Go Theorem for an Accelerating Universe through a Nonlinear Backreaction (2006)
Kasai, Masumi, Asada, Hideki, Futamase, Toshifumi
The backreaction of nonlinear inhomogeneities to the cosmic expansion is re-analyzed in the framework of general relativity. Apparent discrepancies regarding the effect of the nonlinear backreaction,...
Inversion formula for determining parameters of an astrometric binary (2004)
Asada, Hideki, Akasaka, Toshio, Kasai, Masumi
It is believed that some numerical technique must be employed for the determination of the system parameters of a visual binary or a star with a planet because the relevant equations are not only...
Euclidean Algorithm for a Gravitational Lens in a Polynomial Equation (2004)
Asada, Hideki, Kasai, Taketoshi, Kasai, Masumi
The Euclidean algorithm in algebra is applied to a class of gravitational lenses for which the lens equation consists of any set of coupled polynomial equations in the image position. In general,...
Separability of Rotational Effects on a Gravitational Lens (2003)
Asada, Hideki, Kasai, Masumi, Yamamoto, Tatsuya
We derive the deflection angle up to $O(m^2a)$ due to a Kerr gravitational lens with mass $m$ and specific angular momentum $a$. It is known that at the linear order in $m$ and $a$ the Kerr lens is...
Images for an Isothermal Ellipsoidal Gravitational Lens from a Single Real Algebraic Equation (2002)
Asada, Hideki, Hamana, Takashi, Kasai, Masumi
We present explicit expressions for the lens equation for a cored isothermal ellipsoidal gravitational lens as a single real sixth-order algebraic equation in two approaches; 2-dimensional Cartesian...
Do relativistic corrections affect microlensing amplification? (2000)
Ebina, Junya, Osuga, Takeaki, Asada, Hideki, Kasai, Masumi
Studies of gravitational microlensing are usually based on the lens equation, which is valid only to first order in the gravitational constant $G$. However, the amplification factor of microlensing...
Can we see a rotating gravitational lens? (2000)
It is known that the rotation of a gravitational lens affects properties of images. We consider an inverse problem: If the lens is dark, can we infer its rotation from the observed images? We find...
Lagrangian description of the fluid flow with vorticity in the relativistic cosmology (1999)
We develop the Lagrangian perturbation theory in the general relativistic cosmology, which enables us to take into account the vortical effect of the dust matter. Under the Lagrangian representation...
Non-linear vorticity-density coupling in Lagrangian dynamics (1997)
We present a general Lagrangian formalism that allows the treatment of vorticity. We give solutions for the rotational perturbations up to the third-order in a flat background universe. We show how...
Relativistic Zel'dovich approximation in spherically symmetric model (1997)
Morita, Masaaki, Nakamura, Kouji, Kasai, Masumi
We compare relativistic approximation methods, which describe gravitational instability in the expanding universe, in a spherically symmetric model. Linear perturbation theory, second-order...