M. Rigoli et Imc. Salavessa, WILLMORE SUBMANIFOLDS OF THE MOBIUS SPACE AND A BERNSTEIN-TYPE THEOREM, Manuscripta mathematica, 81(1-2), 1993, pp. 203-222
We study Willmore immersed submanifolds f : M(m) --> S-n into the n-Mo
bius space, with m greater than or equal to 2, as critical points of a
conformally invariant functional W. We compute the Euler-Lagrange equ
ation and relate this functional with another one applied to the confo
rmal Gauss map of immersions into S-n. We solve a Bernestein-type prob
lem for compact Willmore hypersurfaces of Sn, namely, if There Exists
a is an element of IR(n+2) such that <gamma f, a>not equal 0 on M, whe
re gamma f is the hyperbolic conformal Gauss map and <,> is the Lorent
z inner product of IR(n+2), and if f satisfies an additional condition
, then f(M) is an (n - 1)-sphere.