An Intrinsic Characterization of Bonnet Surfaces Based on a Closed Differential Ideal

The structure equations for a surface are introduced and two required results based on the Codazzi equations are obtained from them. Important theorems pertaining to isometric surfaces are stated and a theorem of Bonnet is obtained. A tranformation formula for the connection forms is developed. It is proved that the angle of deformation must be harmonic. It is shown that the differentials of many of the important variables generate a closed differential ideal. This implies that a coordinate system exists in which many of the variables satisfy particular ordinary differential equations and these results can be used to characterize Bonnet surfaces.