Base of a deformation

A conjugate net on a surface $F$ and its deformation $F^*$ outside their points of congruence. The base of a deformation is characterized by the fact that the bend — the relation between the normal curvatures $k$ and $k^*$ at isometrically-corresponding points of $F$ and $F^*$ along corresponding directions — has extremal values along the directions of the base of the deformation.

References

[1]	V.F. Kagan, "Foundations of the theory of surfaces in a tensor setting" , 2 , Moscow-Leningrad (1948) (In Russian)

Comments

For more references on the topic of deforming or bending surfaces, cf. the article Deformation, isometric.