Several results concerning contractible and removable edges in 3-connected finite graphs are extended to infinite graphs. First, we prove that every 3-connected locally finite infinite graph has infinitely many removable edges. Next, we prove that for any 3-connected graph , if is a finite degree vertex in and is not incident to any contractible edges, then is a finite cycle or contains a border pair. As a result, every 3-connected locally finite infinite graph contains infinitely many contractible edges. Lastly, it is shown that for any 3-connected locally finite infinite graph which is triangle-free or has minimum degree at least 4, the closure of the subgraph induced by all the contractible edges in the Freudenthal compactification of is topologically 2-connected.
机构:
Natl Inst Informat, Global Res Ctr Big Data Math, 2-1-2 Hitotsubashi,Chiyoda Ku, Tokyo 1018430, JapanNatl Inst Informat, Global Res Ctr Big Data Math, 2-1-2 Hitotsubashi,Chiyoda Ku, Tokyo 1018430, Japan
Ando, Kiyoshi
Egawa, Yoshimi
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Tokyo Univ Sci, Dept Appl Math, 1-3 Kagurazaka,Shinjuku Ku, Tokyo 1628601, JapanNatl Inst Informat, Global Res Ctr Big Data Math, 2-1-2 Hitotsubashi,Chiyoda Ku, Tokyo 1018430, Japan