摘要

A surface x: M --> S-n is called a Willmore surface if it is a critic al surface of the Willmore functional. It is well known that any minimal surface is a Willmore surface and that many nonminimal Willmore surfaces exists. In this paper, we establish an integral inequality for compact Willmore surfaces in S-n and obtain a new characterization of the Veronese surface in S-4 as a Willmore surface. Our result reduces to a well-known result in the case of minimal surfaces.