A Course in Topological Combinatorics by Mark de Longueville

A Course in Topological Combinatorics by Mark de Longueville

Author:Mark de Longueville [Longueville, Mark de]
Language: eng
Format: epub, pdf
Tags: Applied, Graphic Methods, Analytic, Algebraic, Geometry, General, Combinatorics, Mathematics, Game Theory, Topology
ISBN: 9781441979100
Google: L3KMSTHvigwC
Publisher: Springer Science & Business Media
Published: 2011-01-02T00:00:00+00:00


Fig. 4.33Splitting the path in the essential part

Therefore, if i and j are even, then we are done. Otherwise, either i or j is odd, or both. We will consider separately the cases in which precisely one of them is odd and in which both are odd.

In the first case, we may assume that i is even and j is odd. We will construct a thrackle drawing of 8 i, 2j . Lemma 4.36 tells us that the drawings of the two cycles C i and C j touch at the common vertex x. We will double the cycle C j in a two-step procedure depicted in Fig. 4.34. First the path of even length j − 1 along C j is doubled using the doubling of edges as before, and then the crossing at the vertex x is modified as shown in the second step.



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