Generalized motion of noncompact hypersurfaces with velocity having arbitrary growth on the curvature tensor
Generalized motion of noncompact hypersurfaces with velocity having arbitrary growth on the curvature tensor
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DOI:
10.2748/tmj/1178225593
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发表时间:
1995-06
影响因子:
0.5
通讯作者:
H. Ishii;P. Souganidis
中科院分区:
文献类型:
--
作者:
H. Ishii;P. Souganidis
In this note we study the generalized motion of noncompact hypersurfaces with normal velocity depending on the normal direction and the curvature tensor. This work extends the by-now-classical works of Evans and Spruck (for mean curvature) and Chen, Giga and Goto (for general motions with sublinear curvature dependence), because it allows general dependence on the curvature tensor. It also allows a general treatment of the generalized evolution including noncompact hypersurfaces. A number of results regarding no interior, convexity, etc. are also presented. Introduction. During the past few years there has been a substantial progress in understanding the evolution of surfaces, moving with normal velocity depending on the curvature tensor and the normal direction, past the first time singularities occur. The so-called level set approach, which is based on characterizing the surfaces as a level set (for definiteness the zero level set) of the solution of certain fully nonlinear degenerate parabolic PDE's, was developed successfully by Evans and Spruck [ES] for motions by mean curvature and by Chen, Giga and Goto [CGG] for more general evolutions, in which, however, the normal velocity depends, at most linearly, on the curvature tensor. The basic tool of [ES] and [CGG] is the theory of viscosity solutions. We refer to the User's Guide by Crandall, Ishii and Lions [CIL] for a general discussion of the theory of viscosity solutions and its scope, to [ES] and [CGG] for the origin of the level set approach and to Soner [Son] and Barles, Soner and Souganidis [BSS] for alternative formulations, extensions, discussions, etc. Some of the most striking justifications of the generalized motion of hypersurfaces were provided by its use towards obtaining rigorous results regarding the asymptotic behavior of reaction-diffusion equations (see, for example, Evans, Soner and Souganidis [ESS] and Barles, Soner and Souganidis [BSS]) and, more recently, the hydrodynamic limits of particle systems in Katsoulakis and Souganidis [KS1], [KS2] (see also Souganidis [Sou]). The purpose of this note is to extend the results of [CGG] to cases where the * Partially supported by Grant-in-Aid for Scientific Research No. 04640189, The Ministry of Education, Science and Culture, Japan. f Partially suported by NSF grants DMS-9025617 and DMS-9296117 (PYI), ARO contract DAAL 03-90-G-0012 ONR contract N 00014-93-1-0015 and the Alfred P. Sloan Foundation. Part of this work was done while on visit to the Department of Mathematics, Chuo University. 1991 Mathematics Subject Classification. Primary 35K55; Secondary 35K65. 228 H. ISHΠ AND P. E. SOUGANIDIS normal velocity is a general continuous function of the normal vector and the curvature tensor. Such evolutions arise very naturally in geometry, since they include, for example, the Gaussian curvature, as well as in applications like image processing (see, for example, Lions [L] and Alvarez, Guichard, Lions and Morel [AGLM]), etc. The main difficulty in studying such evolutions is that they give rise to PDE's with singularities of order higher than the one's considered by [ES], [CGG], etc. To overcome this difficulty, we extend the class of admissible test functions in the definition of viscosity solutions and then prove a comparison principle as well as an existence result in this class. A new feature of the level set approach here is that our uniqueness result concerning the zero level sets of solutions of nonlinear PDE's is sharp enough to treat the generalized evolutions of noncompact hypersurfaces. As a result, our arguments are slightly more natural than those in Ilmanen [I] concerning generalized evolutions of noncompact hypersurfaces. The paper is organized as follows: In Section 1 we formulate the problem, give the definitions and recall basic facts from the theory of viscosity solutions adapted to our setting. We also recall the definition of the level set approach to the generalized motion of hypersurfaces. Finally, we present a number of examples of motions of hypersurfaces which can be put in our framework. In Section 2 we state and prove our main results, namely, a comparison principle for viscosity solutions as well as a general existence result. Finally, in Section 3 we state a number of results regarding the regularity properties of the generalized evolution. At about the time when this work was completed, Goto [G] proved similar results but in the case of compact interfaces. Goto's approach, which is different from ours, is based on introduction of a notion of finite speed of propagation for the evolution. The authors would like to thank the referee for pointing out an error in the original version of proof of Theorem 1.7 and for making suggestions for us to improve English expressions in this paper. 1. Formulation of the problem, definitions and basic facts. We consider the nonlinear equation (1.1) ut + F{Du,D u) = 0 in β τ = Ωx(0, Γ), where T>0, Ω is an open subset of R, ut, Du and D u denote the time derivative, the spatial gradient and the spatial Hessian of the unknown function κ: ί2x[0,T]^Λ respectively, F: RxS^>R is a given function and S denotes the space of NxN symmetric matrices. Throughout the paper we will be assuming that (1.2) Fe C(J0), where Jo = (R \{0}) x S , )F is elliptic, i.e., for all peR\{0} and X, YeS , ( L 3 ) [ifXF(p, Y), GENERALIZED MOTION OF NONCOMPACT HYPERSURFACES 229