Null type framed surfaces in Minkowski 3-space (Extension of the Singularity theory)

Abstract

In this paper, we define null type framed surfaces in Minkowski 3-space and give a classification of null type framed base surfaces. Null type framed base surfaces contain regular null surfaces, but they are allowed to have singularities. Then we define the Bertrand offsets of null tangent developables, whose striction curves are null, and give some properties of Bertrand offsets.