An edge or face of an embedded graph is light if the sum of the degrees of the vertices incident with it is small. This paper parallelizes four inequalities on the number of light edges and light triangles from the plane to the projective plane. Each of the four inequalities is shown to be the best
On Light Edges and Triangles in Planar Graphs of Minimum Degree Five
β Scribed by Oleg V. Borodin; Daniel P. Sanders
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 342 KB
- Volume
- 170
- Category
- Article
- ISSN
- 0025-584X
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β¦ Synopsis
Abstract
This paper presents two tight inequalities for planar graphs of minimum degree five. An edge or face of a plane graph is light if the sum of the degrees of the vertices incident with it is small. A light edge inequality is presented which shows that planar graphs of minimum degree five have a large number of light edges; a graph is presented which shows that this inequality cannot be improved. This completes work contributed to by Wernicke, GrΓΌnbaum, Fisk, and Borodin. A graph is presented which shows that a similar light triangle inequality of Borodin is best possible; no such graph had been previously found.
π SIMILAR VOLUMES
## Abstract A graph __H__ is light in a given class of graphs if there is a constant __w__ such that every graph of the class which has a subgraph isomorphic to __H__ also has a subgraph isomorphic to __H__ whose sum of degrees in __G__ is β€β__w__. Let $\cal G$ be the class of simple planar graphs