Functionals on Closed 2-Surfaces

We show that the 2-torus in ${\mathbb{R}}^3$ is a critical point of a sequence of functionals ${\mathcal{F}}_n$ ($n=1,2,3,\cdots$) defined over compact 2-surfaces in ${\mathbb{R}}^3$. When the Lagrange function $\mathcal{E}$ is a polynomial of degree $n$ of the mean curvature $H$ of the surface, the radii ($a,r$) of the 2-torus are related as $\frac{a^2}{r^2}=\frac{n^2-n}{n^2-n-1}, n \ge 2$. If the Lagrange function depends on both mean and Gaussian curvatures, the 2- torus remains to be a critical point of ${\mathcal{F}}_n$ without any constraints on the radii of the torus.