论小属曲面中 1- 嵌入图的受限匹配扩展

Pub Date : 2024-07-22 DOI:10.1016/j.disc.2024.114172
Jiangyue Zhang, Yan Wu, Heping Zhang
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A graph <em>G</em> is <em>1-embeddable</em> in a surface Σ if <em>G</em> can be drawn in Σ so that every edge of <em>G</em> crosses at most one other edge at a point. R.E.L. Aldred and M.D. Plummer <span><span>[1]</span></span>, <span><span>[2]</span></span> investigated the properties <span><math><mi>E</mi><mo>(</mo><mi>m</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> for graphs embedded in the plane, torus, projective plane and Klein bottle. In this paper, we study the property <span><math><mi>E</mi><mo>(</mo><mi>m</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> for 1-embeddable graphs in surfaces with small genus. It is shown that no 1-embeddable graph in the plane or projective plane is <span><math><mi>E</mi><mo>(</mo><mn>4</mn><mo>,</mo><mn>1</mn><mo>)</mo></math></span> and no 1-embeddable graph in the torus or Klein bottle is <span><math><mi>E</mi><mo>(</mo><mn>5</mn><mo>,</mo><mn>1</mn><mo>)</mo></math></span>. 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引用次数: 0

摘要

设 是一个至少有顶点的连通图,且包含一个完美匹配。那么,对于每一对大小分别为 和 的不相邻匹配,都存在一个完美匹配,使得 和 。如果可以在 Σ 中画出一条边,使得每条边最多与另一条边相交于一点,则该图位于曲面 Σ 中。R.E.L. Aldred 和 M.D. Plummer 研究了嵌入平面、环面、投影面和克莱因瓶中的图的性质。在本文中,我们研究了小属的曲面中 1-embeddable 图形的性质。结果表明,平面或投影面中没有 1-embeddable 图形,环面或克莱因瓶中也没有 1-embeddable 图形。作为推论,平面或投影面中没有 1- 嵌入图是 5- 可扩展的,环面或克莱因瓶中没有 1- 嵌入图是 6- 可扩展的。一些例子表明,这样的结果是最有可能的。
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On restricted matching extension of 1-embeddable graphs in surfaces with small genus

Let G be a connected graph with at least 2(m+n+1) vertices that contains a perfect matching. Then G is E(m,n) if for each pair of disjoint matchings M,NE(G) of size m and n, respectively, there exists a perfect matching F in G such that MF and FN=. A graph G is 1-embeddable in a surface Σ if G can be drawn in Σ so that every edge of G crosses at most one other edge at a point. R.E.L. Aldred and M.D. Plummer [1], [2] investigated the properties E(m,n) for graphs embedded in the plane, torus, projective plane and Klein bottle. In this paper, we study the property E(m,n) for 1-embeddable graphs in surfaces with small genus. It is shown that no 1-embeddable graph in the plane or projective plane is E(4,1) and no 1-embeddable graph in the torus or Klein bottle is E(5,1). As corollaries, no 1-embeddable graph in the plane or projective plane is 5-extendable and no 1-embeddable graph in the torus or Klein bottle is 6-extendable. Some examples show that such results are best possible.

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