## Abstract In this paper, we prove the following result: Every graph obtained by connecting (with any number of edges) two vertex‐disjoint upper‐embeddable graphs graphs with even Betti number is upper‐embeddable.
The n-ordered graphs: A new graph class
✍ Scribed by Anthony Bonato; Jeannette Janssen; Changping Wang
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 147 KB
- Volume
- 60
- Category
- Article
- ISSN
- 0364-9024
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
For a positive integer n, we introduce the new graph class of n‐ordered graphs, which generalize partial n‐trees. Several characterizations are given for the finite n‐ordered graphs, including one via a combinatorial game. We introduce new countably infinite graphs R^(n)^, which we name the infinite random n‐ordered graphs. The graphs R^(n)^ play a crucial role in the theory of n‐ordered graphs, and are inspired by recent research on the web graph and the infinite random graph. We characterize R^(n)^ as a limit of a random process, and via an adjacency property and a certain folding operation. We prove that the induced subgraphs of R^(n)^ are exactly the countable n‐ordered graphs. We show that all countable groups embed in the automorphism group of R^(n)^. © 2008 Wiley Periodicals, Inc. J Graph Theory 60: 204–218, 2009
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