1. Invariants of almost embeddings of graphs in the plane
- Author
-
Alkin, E., Bordacheva, E., Miroshnikov, A., and Skopenkov, A.
- Subjects
Mathematics - Geometric Topology ,Computer Science - Computational Geometry ,Mathematics - Combinatorics ,Mathematics - History and Overview ,57-01, 57-02, 57K20, 55M25, 55S15, 05C10 - Abstract
In this survey we motivate studies of the invariants from the title. A graph drawing in the plane is called an almost embedding if the images of any two non-adjacent simplices (i.e. vertices or edges) are disjoint. We introduce integer invariants of almost embeddings: winding number, cyclic and triodic Wu numbers. We prove some relations between the invariants. We demonstrate connection of these relations to homology of the deleted product of a graph. We construct almost embeddings realizing some values of these invariants. This paper is accessible to mathematicians not specialized in the area (and to students). All the necessary definitions are recalled. We present some ideas of algebraic and geometric topology in a language accessible to non-topologists. However elementary, this paper is motivated by frontline of research; there are some conjectures and an open problem., Comment: 27 pages, many figures, in Russian. The paper belongs to math.AT because the invariants are special cases of the degree; to math.GT because the most closely related papers are 1805.10237 [math.GT], 2205.01013 [math.GT], and almost embeddings are studied in 2303.14503 (math.CO math.GT), 2008.02523 (math.GT math.AT), 1703.06305 (math.GT), 1904.02404 (math.AT math.GT), 2206.13486 (math.GT math.CO)
- Published
- 2024