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Long Cycles in Graphs on a Fixed Surface

✍ Scribed by Thomas Böhme; Bojan Mohar; Carsten Thomassen


Publisher
Elsevier Science
Year
2002
Tongue
English
Weight
117 KB
Volume
85
Category
Article
ISSN
0095-8956

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✦ Synopsis


We prove that there exists a function a: N 0 × R + Q N such that (i) If G is a 4-connected graph of order n embedded on a surface of Euler genus g such that the face-width of G is at least a(g, e), then G can be covered by two cycles each of which has length at least (1 -e) n.

We apply this to derive lower bounds for the length of a longest cycle in a graph G on any fixed surface. Specifically, there exist functions b: N 0 Q N and c: N 0 Q R + such that for every graph G on n vertices that is embedded on a surface of Euler genus g the following statements hold:

(ii) If G is 4-connected, then G contains a collection of at most b(g) paths which cover all vertices of G, and G contains a cycle of length at least n/b(g).

Moreover, for each e > 0, every 4-connected graph G with sufficiently large face-width contains a spanning tree of maximum degree at most 3 and a 2-connected spanning subgraph of maximum degree at most 4 such that the number of vertices of degree 3 or 4 in either of these subgraphs is at most e |V(G)|.


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