Quenching time of some nonlinear wave equations

Firmin K. N’gohisse and Théodore K. Boni

Université d’Abobo-Adjamé UFR-SFA, Département de Mathématiques et Informatiques BP 801 Abidjan 02, (Côte d’Ivoire)
Institut National Polytechnique Houphouët-Boigny de Yamoussoukro BP 1093 Yamoussoukro, (Côte d’Ivoire)


Abstract: In this paper, we consider the following initial-boundary value problem \[ {\left\rbrace \begin{array}{ll} u_{tt}(x,t)=\varepsilon Lu(x,t)+f\big (u(x,t)\big )\quad \mbox {in}\quad \Omega \times (0,T)\,,\\ u(x,t)=0 \quad \mbox {on}\quad \partial \Omega \times (0,T)\,, \\ u(x,0)=0 \quad \mbox {in}\quad \Omega \,, \\ u_t(x,0)=0 \quad \mbox {in}\quad \Omega \,, \end{array}\right.}\] where $\Omega $ is a bounded domain in $\mathbb{R}^N$ with smooth boundary $\partial \Omega $, $L$ is an elliptic operator, $\varepsilon $ is a positive parameter, $f(s)$ is a positive, increasing, convex function for $s\in (-\infty ,b)$, $\lim _{s\rightarrow b}f(s)=\infty $ and $\int _0^b\frac{ds}{f(s)}<\infty $ with $b=\operatorname{const}>0$. Under some assumptions, we show that the solution of the above problem quenches in a finite time and its quenching time goes to that of the solution of the following differential equation \[ {\left\rbrace \begin{array}{ll} \alpha ^{\prime \prime }(t)=f(\alpha (t))\,,&\quad t>0\,, \\ \alpha (0)=0\,,\quad \alpha ^{\prime }(0)=0\,, \end{array}\right.}\] as $\varepsilon $ goes to zero. We also show that the above result remains valid if the domain $\Omega $ is large enough and its size is taken as parameter. Finally, we give some numerical results to illustrate our analysis.

AMSclassification: primary 35B40; secondary 35B50, 35L20, 35L70, 65M06.

Keywords: nonlinear wave equations, quenching, convergence, numerical quenching time.