Principal configurations around umbilics of spacelike surfaces in null hypersurfaces of ${\mathbb{R}}_1^4$

Matias Navarro, Oscar Palmas, Didier A. Solis

We study the principal configurations around an isolated $\eta$-umbilical point on a generic spacelike surface $S$ immersed in a null hypersurface $M$ of Minkowski space $\mathbb{R}_1…