arXiv subjects

Tetu Makino

Publications and source records attributed to Tetu Makino.

24 records · Page 2Linked to original sources

arXiv2016

On a certain type of nonlinear hyperbolic equations derived from astrophysical problems

Investigations of spherically symmetric motions of self-gravitating gaseous stars governed by the non-relativistic Newtonian gravitation theory or by the general relativistic theory lead us to a certain type of non-linear hyperbolic equations defined on a finite interval of the space variable. The linearized principal part has regular singularities at the both ends of the interval of the space variable. But the regularity loss caused by the singularities at the boundaries requires application of the Nash-Moser technique. An abstract unified treatment of the problem is presented.

math.AP↗

arXiv2015

On the time evolution of a homogeneous isotropic gaseous universe

We investigate the time evolution of a homogeneous isotropic universe which consists of a perfect gas governed by the Einstein-Euler-de Sitter equations. Under suitable assumptions on the equation of state and assumptions on the present states, we give a mathematically rigorous proof of the existence of the Big Bang at the finite past and expanding of the universe in the course to the infinite future.

math.AP↗

arXiv2015

On Spherically Symmetric Motions of the Atmosphere Surrounding a Planet Governed by the Compressible Euler Equations

We consider spherically symmetric motions of inviscid compressible gas surrounding a solid ball under the gravity of the core. Equilibria touch the vacuum with finite radii, and the linearized equation around one of the equilibria has time-periodic solutions. To justify the linearization, we should construct true solutions for which this time-periodic solution plus the equilibrium is the first approximation. But this leads us to difficulty caused by singularities at the free boundary touching the vacuum. We solve this problem by the Nash-Moser theorem.

math.AP↗

arXiv2014

A Note on a Modified Catuskoti

The `catuskoti' or tetralemma in Buddhist logic is a problematic subject from the modern logical point of view. Recently a many-valued paraconsistent logic was proposed in order to formalize catuskoti adequately by G. Priest. On the other hand a slight modification of the formalization of catuskoti seems to allow an appropriate interpretation in the framework of the classical propositional calculus in the mathematical logic developed by Russell-Whitehead and Hilbert-Ackermann.

math.LO↗

arXiv2014

On spherically symmetric motions of a gaseous star governed by the Euler-Poisson equations

We study spherically symmetric motions of a gaseous star governed by the Euler-Poisson equations. Equilibria are given as solutions of the Lane-Emden equations, and the linearized equation around one of these equilibria admits time-periodic solutions. To justify the linearization, we should construct true solutions of the nonlinear evolution equation for which this time-periodic solutions plus the equilibrium is the first approximation. To do so, we apply the Nash-Moser theory. We presents a partial result under some assumptions on the adiabatic exponent of the gas, and propose an open problem to be studied in the future.

math.AP↗

arXiv2013

An Application of Nash-Moser Theorem to Smooth Solutions of One-Dimensional Compressible Euler Equation with Gravity

We study one-dimensional motions of polytropic gas governed by the compressible Euler equations. The problem on the half space under a constant gravity gives an equilibrium which has free boundary touching the vacuum and the linearized approximation at this equilibrium gives time periodic solutions. But it is not easy to justify the existence of long-time true solutions for which this time periodic solution is the first approximation. The situation is in contrast to the problem of free motions without gravity. The reason is that the usual iteration method for quasilinear hyperbolic problem cannot be used because of the loss of regularities which causes from the touch with the vacuum. Interestingly, the equation can be transformed to a nonlinear wave equation on a higher dimensional space, for which the space dimension, being larger than 4, is related to the adiabatic exponent of the original one-dimensional problem. We try to find a family of solutions expanded by a small parameter. Applying the Nash-Moser theory, we justify this expansion.The application of the Nash-Moser theory is necessary for the sake of conquest of the trouble with loss of regularities, and the justification of the applicability requires a very delicate analysis of the problem.

math.AP↗