Discrete Mathematics ( IF 0.8 ) Pub Date : 2021-06-19 , DOI: 10.1016/j.disc.2021.112516 Vladimir P. Korzhik
A graph drawn on the plane is 2-immersed in the plane if each edge is crossed by at most two other edges. By a proper 2-immersion of a graph we mean a 2-immersion of the graph in the plane such that there is at least one crossing point. We consider the class of all finite graphs triangulating the plane such that the graphs have no loops and multiple edges, the vertices have degree 5 and 6 only, and the distance between any two 5-valent vertices is at least 4. In this series of papers we construct graphs of the class having no proper 2-immersions. In the present paper we obtain a necessary condition for a graph of the class to have a proper 2-immersion. Then we construct a graph of the class that does not satisfy the necessary condition thereby obtaining a planar graph having no proper 2-immersions.
中文翻译:
平面图在平面中没有适当的 2 浸。三
如果每条边最多与其他两条边交叉,则绘制在平面上的图形是 2-浸入平面中。图形的适当的2-浸入是指图形在平面中的2-浸入使得至少有一个交叉点。我们考虑类 在所有有限图中对平面进行三角剖分,使得图没有环和多条边,顶点只有度数 5 和 6,并且任意两个 5 价顶点之间的距离至少为 4。 在本系列论文中,我们构造图班级的 没有适当的 2 次浸泡。在本文中,我们获得了类图的必要条件有一个适当的 2 沉浸。然后我们构造一个类的图 不满足必要条件,从而得到一个没有适当的 2-浸入的平面图。