There are many nonlinear parabolic equations whose solutions develop singularity in finite time, say T. In many cases, a certain norm of the solution tends to infinity as time t approaches T. Such a phenomenon is called blow-up, and T is called the blow-up time. This paper is concerned with approximation of blow-up phenomena in nonlinear parabolic equations. For numerical computations or for other reasons, we often have to deal with approximate equations. But it is usually not at all clear if such wild phenomena as blow-up can be well reflected in the approximate equations. In this paper we present rather simple but general sufficient conditions which guarantee that the blow-up time for the original equation is well approximated by that for approximate equations. We will then apply our result to various examples.
§1. Introduction and Main ResultsThere is a large number of nonlinear partial differential equations of parabolic type whose solution for a given initial data cannot be extended globally in time and develop a singularity in finite time, say T. Such a phenomenon is called blow-up and T is called the blow-up time. In many cases, some norms of blow-up solutions tend to infinity as t approaches T.Blow-up is known to occur in various equations including those in combustion theory, chemotaxis models and equations describing crystalline formation involving curvature-driven motion (see [9], [39]). The study of blow-up phenomena is not only interesting from the mathematical point of view but also Communicated by H. Okamoto, March 9, 2000. Revised April 20, 2000. 1991 Generally speaking, it is very difficult to numerically simulate blow-up phenomena accurately. For one thing, one has to deal with numerical data that grow indefinitely as the blow-up time approaches. This is obviously not an easy task. Secondly -and more importantly -it is not at all clear if features of such a wild phenomenon as blow-up can be well reflected in the discretized equation which approximate the original equation. Most of the standard error estimates become useless as t approaches the blow-up time.There have been some attempts to establish numerical methods to capture blow-up phenomena. For example, the rescaling algorithm by Berger and Kohn [10] and the method of MMPDE [12] by Budd et al can observe the shape of blow-up solutions near the blow-up time. There are also some works concerning approximation of blow-up time. Some authors studied numerical blow-up time and its convergence. As for the semilinear parabolic equation ut = u xx + u p , Nakagawa [35] (p = 2) and Chen [13] (p > 1) studied a finite difference scheme for this equation and proved the convergence of the blow-up time of approximate solutions to that of the real solution. They assumed that L q (q = I or 2) norm of the solution diverges at blow-up time. This assumption, however, does not always hold [17]. Recently, Abia, Lopez-Marcos and Martinez [1] considered a one dimensional semi-discrete problem for this equation. Here a semi-discrete problem means the syste...