Additional First-Order Equation for Infinitesimal Bendings of Smooth Surfaces in the Isothermal Coordinates
摘要
The article contributes to the theory of infinitesimal bendings of smoothsurfaces in Euclidean 3-space.We derive a first-order linear differential equation, which previouslydid not appear in the literature and which is satisfied by any Darbouxrotation field of a smooth surface.We show that, for some surfaces, this additional equation is functionallyindependent of the three standard equations that the Darboux rotationfield satisfies (and by which it is determined).As a consequence of this additional equation, we prove the maximumprinciple for the components of the Darboux rotation field for a classof disk-homeomorphic surfaces containing not only surfaces of positive Gaussian curvature.