We first prove that a properly immersed static
-dimensional
submanifold
with restricted growth of the curvature at infinity in
is totally
umbilical if the Willmore functional is pinched by a positive constant depending only
on
.
Secondly, we obtain a global rigidity theorem for Willmore surfaces in the sphere.
Thirdly, we give a lower bound on the lifespan of the surface diffusion flow in
.
Finally, we get the longtime existence and convergence of the surface diffusion flow in
under
the small initial Willmore energy condition.
Dedicated to Professor Duanzhuang Qian
on his 110th anniversary.
Keywords
surface diffusion, Willmore surface, gap theorem,
convergence theorem.