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Hiroyuki Takamura

Publications and source records attributed to Hiroyuki Takamura.

At least 19 recordsLinked to original sources
arXiv2026

A revisit via slicing method on a quadratic semilinear wave equation in two space dimensions

In this paper, we are focusing on the proof of the blow-up result for a quadratic semilinear wave equation in two space dimensions. There is a logarithmic loss in estimating the lifespan of classical solutions if the 0th moment of the initial speed does not vanish. This result is already known with almost sharp constants. But in order to have a direct application to numerical analysis, we show a simple proof by iteration argument of point-wise estimate of the solution with the slicing technique.

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arXiv2026

Lifespan estimate for one dimensional wave equation with semilinear terms of spatial derivative

This paper studies the upper and lower bounds of the lifespan for the classical solutions to the initial value problems of one dimensional wave equations with non-autonomous semilinear terms including the space-derivative of the unknown function.This is a non-trivial business comparing to the analogous results with time-derivative type semilinear terms, especially for the proof to obtain the sharp upper bound of the lifespan as we have to deal with space dependent weights among iteration procedures of the weighted functional of the solution. Also it is surprising that a part of them reaches to the same ordinary differential inequality for classical semilinear damped wave equations introduced by Li and Zhou (Discrete Contin. Dynam. Systems, 1995, 1(4): 503-520), and we show a simple proof for blow up result from this ordinary differential inequality by iteration argument and slicing method in more general situation.

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arXiv2026

Blow-up of solutions to the Euler-Poisson-Darbox equation with critical power nonlinearity

In our recent precious work, we established the finite time blow up result and upper bound of lifespan estimate to the singular Cauchy problem of semilinear Euler-Poisson-Darboux equation in R^n with subcritical power type nonlinearity. By introducing an improved test function, we obtain an enhanced lower bound for the functional including the spacetime integral of the nonlinear term with an additional logarithmic growth, which finally yields the blow up result and upper bound of lifespan estimate for the corresponding Cauchy problem with "critical" nonlinear power. And this gives some partial answer to the open problem 1 posed by D'Abbicco (J. Differential Equations 286 (2021), 531-556).

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arXiv2025

A revisit on the critical blow-up for semilinear wave equations in low space dimensions with slicing method

In this reviewing paper, we are interested in the proof of estimating the lifespan of classical solutions of semilinear wave equations with the critical exponent from above especially in low space dimensions. There are a few ways to show the result by comparison argument with ODE via point-wise estimates, or by functional method via weak form with the special choice of the test function. But in order to have direct applications to the numerical analysis, we show the simple proof by iteration argument of point-wise estimates of the solution with the slicing technique.

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arXiv2024

Note on the existence of classical solutions of derivative semilinear models for one dimensional wave equation

This note is a supplement with a new result to the review paper by Takamura [13] on nonlinear wave equations in one space dimension. We are focusing here to the long-time existence of classical solutions of semilinear wave equations in one space dimension, especially with derivative nonlinear terms of product-type. Our result is an extension of the single component case, but it is meaningful to provide models as possible as many to cover the optimality of the general theory. The proof is based on the classical iteration argument of the point-wise estimate of the solution.

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arXiv2024

Blow-up of classical solutions of quasilinear wave equations in one space dimension

This paper studies the upper bound of the lifespan of classical solutions of the initial value problems for one dimensional wave equations with quasilinear terms of space-, or time-derivatives of the unknown function. The results are same as those of the semilinear case. But it is quite meaningful to consider this kind of problems for the purpose to cover the optimality of the general theory for nonlinear wave equations by many model equations as far as possible.

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arXiv2024

Blow-up of solutions to semilinear wave equations with spatial derivatives

For small-amplitude semilinear wave equations with power type nonlinearity on the first-order spatial derivative, the expected sharp upper bound on the lifespan of solutions is obtained for both critical cases and subcritical cases, for all spatial dimensions $n>1$. It is achieved uniformly by constructing the integral equations, deriving the ordinary differential inequality system, and iteration argument. Combined with the former works, the sharp lifespan estimates for this problem are completely established, at least for the spherical symmetric case.

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arXiv2024

A blow-up result for the semilinear Euler-Poisson-Darboux-Tricomi equation with critical power nonlinearity

In this paper, we prove a blow-up result for a generalized semilinear Euler-Poisson-Darboux equation with polynomially growing speed of propagation, when the power of the semilinear term is a shift of the Strauss' exponent for the classical semilinear wave equation. Our proof is based on a comparison argument of Kato-type for a second-order ODE with time-dependent coefficients, an integral representation formula by Yagdjian and the Radon transform. As byproduct of our method, we derive upper bound estimates for the lifespan which coincide with the sharp one for the classical semilinear wave equation in the critical case.

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arXiv2024

Recent developments on the lifespan estimate for classical solutions of nonlinear wave equations in one space dimension

In this paper, we overview the recent progresses on the lifespan estimates of classical solutions of the initial value problems for nonlinear wave equations in one space dimension. There are mainly two directions of the developments on the model equations which ensure the optimality of the general theory. One is on the so-called "combined effect" of two kinds of the different nonlinear terms, which shows the possibility to improve the general theory. Another is on the extension to the non-autonomous nonlinear terms which includes the application to nonlinear damped wave equations with the time-dependent critical case.

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arXiv2023

The combined effect in one space dimension beyond the general theory for nonlinear wave equations

In this paper, we show the so-called "combined effect" of two different kinds of nonlinear terms for semilinear wave equations in one space dimension. Such a special phenomenon appears only in the case that the total integral of the initial speed is zero. It is remarkable that, including the combined effect case, our results on the lifespan estimates are partially better than those of the general theory for nonlinear wave equations.

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arXiv2023

The generalized combined effect for one dimensional wave equations with semilinear terms including product type

We are interested in the so-called "combined effect" of two different kinds of nonlinear terms for semilinear wave equations in one space dimension. Recently, the first result with the same formulation as in the higher dimensional case has been obtained if and only if the total integral of the initial speed is zero, namely Huygens' principle holds. In this paper, we extend the nonlinear term to the general form including the product type. Such model equations are extremely meaningful only in one space dimension because the most cases in higher dimensions possess the global-in-time existence of a classical solution in the general theory for nonlinear wave equations. It is also remarkable that our results on the lifespan estimates are partially better than those of the general theory. This fact tells us that there is a possibility to improve the general theory which was expected complete more than 30 years ago.

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arXiv2023

The lifespan of classical solutions of one dimensional wave equations with semilinear terms of the spatial derivative

This paper is devoted to the lifespan estimates of small classical solutions of the initial value problems for one dimensional wave equations with semilinear terms of the spatial derivative of the unknown function. It is natural that the result is same as the one for semilinear terms of the time-derivative. But there are so many differences among their proofs. Moreover, it is meaningful to study this problem in the sense that it may help us to investigate its blow-up boundary in the near future.

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arXiv2022

On a semilinear wave equation in anti-de Sitter spacetime: the critical case

In the present paper we prove the blow-up in finite time for local solutions of a semilinear Cauchy problem associated with a wave equation in anti-de Sitter spacetime in the critical case. According to this purpose, we combine an ODI result with an iteration argument, by using an explicit integral representation formula for the solution to a linear Cauchy problem associated with the wave equation in anti-de Sitter spacetime in one space dimension.

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arXiv2022

A note on blow-up results for semilinear wave equations in de Sitter and anti-de Sitter spacetimes

In this work we derive some blow-up results for semilinear wave equations both in de Sitter and anti-de Sitter spacetimes. By requiring suitable conditions on a time-dependent factor in the nonlinear term, we prove the blow-up in finite time of the spatial averages of local in time solutions. In particular, we derive a sequence of lower bound estimates for the spatial average by combining a suitable slicing procedure with an iteration frame for this time-dependent functional.

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