The Curvatures of Some Skew Fundamental Forms

Tilla Klotz Milnor
1977 Proceedings of the American Mathematical Society  
Fix a unit normal vector field on a surface C4-immersed in a Riemannian 3-manifold of constant sectional curvature. Suppose H and K are mean and Gauss curvatures respectively, and that H' = V/72 -K. Wherever H' •> 0, define I', II' and III' by HI = II -HI, H'W = H\\ -K\ and III' = Hit -XT, where I and II are the first and second fundamental forms. For constants a, ß, and v, let A' = at + ßlt + yïlt. Wherever H' ¥= 0 and A' is nondegenerate, the curvature of this (not necessarily Riemannian)
more » ... ic A' is computed in terms of K(t) and more familiar quantities on the surface. Some discussion of K(t) is also included.
doi:10.2307/2041037 fatcat:yvzjfc6xkbbavl757btdw3s4k4