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Junichi Harada

Publications and source records attributed to Junichi Harada.

11 recordsLinked to original sources
arXiv2025

Oscillatory behavior of solutions to the critical Fujita equation in 6D

Long time dynamics of solutions to the 6D energy critical heat equation $u_t=\Delta u+|u|^{p-1}u$ on $\R^6\times(0,\infty)$ is investigated. It is shown that there exists a radially symmetric global solution $u(x,t)\in C([0,\infty);\dot H^1(\R^6))$ of the form \begin{align*} u(x,t) = \lambda(t)^{-\frac{n-2}{2}} {\sf Q}(\tfrac{x}{\lambda(t)}) + \text{error} (x,t), \end{align*} where the function \( \lambda(t) \) satisfies: \begin{itemize} \item $\dis\lim_{t\to\infty}\|\text{error}(\cdot,t)\|_{\dot H_x^1(\R^6)}=0$, \item $\dis\liminf_{t\to\infty}\lambda(t)=0$, \item $\dis\limsup_{t\to\infty}\lambda(t)=\infty$. \end{itemize} The solutions constructed here demonstrate that the dynamical behavior in \( \dot H^1(\mathbb{R}^n) \) can differ significantly from the behavior in \( H^1(\mathbb{R}^n) \).

math.AP↗
arXiv2024

Dynamics near the ground state for the Sobolev critical Fujita type heat equation in 6D

This paper investigates the asymptotic behavior of solutions to $u_t=\Delta u+|u|^{p-1}u$ in the Sobolev critical case. Our main result is a classification of the dynamics near the ground states in the six dimensional case. It is shown that if the initial data $u_0\in H^1(\mathbb{R}^6)$ satisfies $\|u_0-{\sf Q}\|_{\dot H^1(\mathbb{R}^6)}\ll1$, then the solution falls into one of the following three scenarios: 1) It is globally defined and converge to one of the ground states as $t\to\infty$. 2) It is globally defined and converge to $0$ in $\dot H^1(\mathbb{R}^6)$ as $t\to\infty$. 3) It exhibits finite time blowup with a type I rate. This paper extends the classification result in the case $n\geq7$, previously obtained by Collot-Merle-Rapha\"el, to the borderline case $n=6$.

math.AP↗
arXiv2024

Stability of nondegenerate ODE type blowup for the Fujita type heat equation

The asymptotic bahavior of blowup solutions to the Fujita type heat equation $u_t=\Delta u+|u|^{p-1}u$ is studied. This equation admits the ODE type blowup given by $u(x,t)=(p-1)^\frac{1}{p-1}(T-t)^{-\frac{1}{p-1}}$. It is known that nondegenerate ODE type blowup is stable if $p\in(1,\frac{n+2}{n-2})$ due to Fermanian Kammerer-Merle-Zaag (2000). This paper extends their result to more general case.

math.AP↗
arXiv2022

Existence of blowup solutions to the semilinear heat equation with double power nonlinearity

We consider the semilinear heat equation $u_t=Δu+|u|^{p-1}u-|u|^{q-1}u$ in $\mathbb{R}^n\times(0,T)$, where $n=5$, $p=\frac{n+2}{n-2}$ and $q\in(0,1)$. By the presence of $-|u|^{q-1}u$, this equation has a finite time extinction property. We show the existence of a new type of blowup solutions by using this property. In fact, we obtain such blowup solutions by connecting a specific blowup solution of $u_t=Δu+|u|^{p-1}u$ and a specific solution of $u_t=Δu-|u|^{q-1}u$, and by adding correction terms.

math.AP↗
arXiv2020

A type II blowup for the six dimensional energy critical heat equation

We study blowup solutions of the 6D energy critical heat equation $u_t=Δu+|u|^{p-1}u$ in $\R^n\times(0,T)$. A goal of this paper is to show the existence of type II blowup solutions predicted by Filippas, Herrero and Velázquez \cite{FilippasHV}. The dimension six is a border case whether a type II blowup can occur or not. Therefore the behavior of the solution is quite different from other cases. In fact, our solution behaves like \[ u(x,t)\approx \begin{cases} λ(t)^{-2}{\sf Q}(λ(t)^{-1}x) & \text{in the inner region: } |x|\simλ(t), -(p-1)^\frac{1}{p-1}(T-t)^{-\frac{1}{p-1}} & \text{in the selfsimilar region: } |x|\sim\sqrt{T-t} \end{cases} \] with $λ(t)=(1+o(1))(T-t)^\frac{5}{4}|\log(T-t)|^{-\frac{15}{8}}$. The local energy $E_\text{loc}(u) =\frac{1}{2}\|\nabla u\|_{L^2(|x|<1)}^2-\frac{1}{3}\|u\|_{L^3(|x|<1)}^3$ of the solution goes to $-\infty$.

math.AP↗
arXiv2019

A higher speed type II blowup for the five dimensional energy critical heat equation

This paper is concerned with blow-up solutions of the five dimensional energy critical heat equation $u_t=Δu+|u|^\frac{4}{3}u$. A goal of this paper is to show the existence of type II blowup solutions which behave as $\|u(t)\|_\infty\sim(T-t)^{-3k}$ ($k=2,3,\cdots$). Our solutions are the same one formally derived by Filippas, Herrero and Velázquez \cite{Filippas}.

math.AP↗
arXiv2019

Resource Optimization of Product Development Projects with Time-Varying Dependency Structure

Project managers are continuously under pressure to shorten product development durations. One practical approach for reducing the project duration is lessening dependencies between different development components and teams. However, most of the resource allocation strategies for lessening dependencies place the implicit and simplistic assumption that the dependency structure between components is static (i.e., does not change over time). This assumption, however, does not necessarily hold true in all product development projects. In this paper, we present an analytical framework for optimally allocating resources to shorten the lead-time of product development projects having a time-varying dependency structure. We build our theoretical framework on a linear system model of product development processes, in which system integration and local development teams exchange information asynchronously and aperiodically. By utilizing a convexity result from the matrix theory, we show that the optimal resource allocation can be efficiently found by solving a convex optimization problem. We provide illustrative examples to demonstrate the proposed framework. We also present boundary analyses based on major graph models to provide managerial guidelines for improving empirical PD processes.

math.OC↗
arXiv2018

Resource Allocation for Containing Epidemics from Temporal Network Data

We study the problem of containing epidemic spreading processes in temporal networks. We specifically focus on the problem of finding a resource allocation to suppress epidemic infection, provided that an empirical time-series data of connectivities between nodes is available. Although this problem is of practical relevance, it has not been clear how an empirical time-series data can inform our strategy of resource allocations, due to the computational complexity of the problem. In this direction, we present a computationally efficient framework for finding a resource allocation that satisfies a given budget constraint and achieves a given control performance. The framework is based on convex programming and, moreover, allows the performance measure to be described by a wide class of functionals called posynomials with nonnegative exponents. We illustrate our theoretical results using a data of temporal interaction networks within a primary school.

cs.SI↗
arXiv2013

Non self-similar blow-up solutions to the heat equation with nonlinear boundary conditions

This paper is concerned with finite blow-up solutions of the heat equation with nonlinear boundary conditions. It is known that a rate of blow-up solutions is the same as the self-similar rate for a Sobolev subcritical case. A goal of this paper is to construct a blow-up solution whose blow-up rate is different from the self-similar rate for a Sobolev supercritical case.

math.AP↗