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A zero-free interval for flow polynomials of cubic graphs

机译:三次图流多项式的零自由间隔

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摘要

Let P(G, t) and F(G, t) denote the chromatic and flow polynomials of a graph G. Woodall has shown that, if G is a plane triangulation, then the only zeros of P(G, t) in (-infinity, gamma) are 0, 1 and 2, where approximate to 2.54...is the zero in (2, 3) of the chromatic polynomial of the octahedron. The main purpose of this paper is to remove the planarity hypothesis from Woodall's theorem by showing that the dual statement holds for both planar and non-planar graphs: if G is a cubic bridgeless graph, then the only zeros of F(G, t) in (-infinity, gamma) are 1 and 2, where y approximate to 2.54... is the zero in (2, 3) of the flow polynomial of the cube. Our inductive proof technique forces us to work with near-cubic graphs, that is to say graphs with minimum degree at least two and at most one vertex of degree greater then three. We also obtain related results concerning the zero distribution of the flow polynomials of near-cubic graphs. (c) 2006 Elsevier Inc. All rights reserved.
机译:令P(G,t)和F(G,t)表示图G的色多项式和流多项式。Woodall表明,如果G是平面三角剖分,则()中P(G,t)的唯一零-infinity,γ)是0、1和2,其中大约2.54 ...是八面体的色多项式(2,3)中的零。本文的主要目的是通过证明对偶图对于平面图和非平面图均成立,从而从Woodall定理中消除平面性假设:如果G是三次无桥图,则F(G,t)的唯一零in(-infinity,gamma)是1和2,其中y约等于2.54 ...是立方体的流量多项式(2,3)中的零。我们的归纳证明技术迫使我们使用近似三次图,即最小度至少为2且最大一个度顶点大于3的图。我们还获得了有关近三次图流多项式的零分布的相关结果。 (c)2006 Elsevier Inc.保留所有权利。

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