图特重铬酸盐
Tutte's dichromate for signed graphs
摘要：
我们引入了“三变量Tutte多项式”的一个有符号的图作为一个不变量的有符号的图顶点切换，其中包含其评价的数量适当的着色和nowhere零流的数量。在这一点上，它平行于图的Tutte多项式，其中包含色多项式和流多项式作为专门化。无处零紧张局势的数量（签署的图，他们不是简单地涉及到适当的着色，因为他们是图）是在评价的三变量Tutte多项式在两个不同的点。有趣的是，有偏图的二元二色多项式，由Zaslavsky所示，与图的Tutte多项式共享许多类似的属性，一般不会产生有符号图的无零流的数量。因此，符号图的“重色”（我们的三元Tutte多项式）不同于重色多项式（秩大小生成函数）。符号图的三元Tutte多项式可以推广到公共基集上的拟阵的序偶的不变量--对于符号图，其基础图的圈拟阵和其框架拟阵形成相应的拟阵对。这个不变量是规范定义的Tutte多项式的拟阵对的共同基础上的一个最近的文件的意义上的Kraubrski，Moffatt和Tanasa，并首先研究了威尔士和Kayibi作为一个四变量连接多项式的拟阵对的共同基础上。
英文摘要：
We introduce the ``trivariate Tutte polynomial" of a signed graph as an invariant of signed graphs up to vertex switching that contains among its evaluations the number of proper colorings and the number of nowhere-zero flows. In this, it parallels the Tutte polynomial of a graph, which contains the chromatic polynomial and flow polynomial as specializations. The number of nowhere-zero tensions (for signed graphs they are not simply related to proper colorings as they are for graphs) is given in terms of evaluations of the trivariate Tutte polynomial at two distinct points. Interestingly, the bivariate dichromatic polynomial of a biased graph, shown by Zaslavsky to share many similar properties with the Tutte polynomial of a graph, does not in general yield the number of nowhere-zero flows of a signed graph. Therefore the ``dichromate" for signed graphs (our trivariate Tutte polynomial) differs from the dichromatic polynomial (the rank-size generating function). The trivariate Tutte polynomial of a signed graph can be extended to an invariant of ordered pairs of matroids on a common ground set -- for a signed graph, the cycle matroid of its underlying graph and its frame matroid form the relevant pair of matroids. This invariant is the canonically defined Tutte polynomial of matroid pairs on a common ground set in the sense of a recent paper of Krajewski, Moffatt and Tanasa, and was first studied by Welsh and Kayibi as a four-variable linking polynomial of a matroid pair on a common ground set.
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