Eulerian-minors and Recursive Characterization of 4-regular Planar Graphs
摘要
In this paper, we first show that Eulerian-minors, constructed from Eulerian subgraphs through edge contractions, preserve Eulerian properties and establish a well-quasi-ordering under the Eulerian-minor relation. Then we concisely characterize Eulerian, planar, and outer-planar Eulerian graphs by excluding Eulerianminors. Furthermore, we introduce a novel planar operation that generates all 4-regular planar graphs from a bouquet consisted of two loops. This significantly simplifies prior methods proposed by Manca and Lehel for generating simple 4-regular planar graphs.