Masaaki Morita

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The effective evolution of an inhomogeneous cosmological model may be described in terms of spatially averaged variables. We point out that in this context, quite naturally, a measure arises which is identical to a fluid model of the Kullback-Leibler relative information entropy, expressing the distinguishability of the local inhomogeneous mass density(More)
The gravitational instability of inhomogeneities in the expanding universe is studied by the relativistic second-order approximation. Using the tetrad formalism we consider irrotational dust universes and get equations very similar to those given in the Lagrangian perturbation theory in Newtonian cosmology. Neglecting the cosmological constant and assuming(More)
We formulate a perturbative approximation to gravitational instability, based on Lagrangian hydrodynamics in Newtonian cosmology. We take account of ‘pressure’ effect of fluid, which is kinematically caused by velocity dispersion, to aim hydrodynamical description beyond shell crossing. Master equations in the Lagrangian description are derived and solved(More)
Takayuki Tatekawa,* Momoko Suda, Kei-ichi Maeda, Masaaki Morita, 2,3,4 and Hiroki Anzai Department of Physics, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan Theoretische Physik, Ludwig-Maximilians-Universität,(More)
The Chaplygin gas model, characterized by an equation of state of the type p = − ρ emerges naturally from the Nambu-Goto action of string theory. This fluid representation can be recast under the form of a tachyonic field given by a Born-Infeld type Lagrangian. At the same time, the Chaplygin gas equation of state can be obtained from a self-interacting(More)
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