arXiv2020
This article introduces planar ribbons, Vergili ribbon complexes and ribbon nerves in Alexandroff-Hopf-Whitehead CW (Closure finite Weak) topological spaces. A {\em planar ribbon} (briefly, {ribbon}) in a CW space is the closure of a pair of nesting, non-concentric filled cycles that includes the boundary but does not include the interior of the inner cycle. Each planar ribbon has its own distinctive shape determined by its outer and inner boundaries and the interior within its boundaries. A Vergili ribbon complex (briefly, ribbon complex) in a CW space is a non-void collection of countable planar ribbons. A ribbon nerve is a nonvoid collection of planar ribbons (members of a ribbon complex) that have nonempty intersection. A planar CW space is a non-void collection of cells (vertexes, edges and filled triangles) that may or may not be attached to other and which satisfy Alexandroff-Hopf-Whitehead containment and intersection conditions. In the context of CW spaces, planar ribbons, ribbon complexes and ribbon nerves are characterized by Betti numbers derived from standard Betti numbers $\mathcal{B}_0$ (cell count), $\mathcal{B}_1$ (cycle count) and $\mathcal{B}_2$ (hole count), namely, $\mathcal{B}_{rb}$ and $\mathcal{B}_{rbNrv}$ introduced in this paper. Results are given for collections of ribbons and ribbon nerves in planar CW spaces equipped with an approximate descriptive proximity, division of the plane into three bounded regions by a ribbon and Brouwer fixed points on ribbons. In addition, the homotopy types of ribbons and ribbon nerves are introduced.