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Lifted, projected and subgraph-induced inequalities for the representatives k-fold coloring polytope

机译:代表k折叠着色多态性的解除,投影和子图引起的不等式

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A k-fold x-coloring of a graph G is an assignment of (at least) k distinct colors from the set {1, 2,..., x} to each vertex such that any two adjacent vertices are assigned disjoint sets of colors. The kth chromatic number of G, denoted by chi(k)(G), is the smallest x such that G admits a k-fold x-coloring. We present an integer linear programming formulation (ILP) to determine chi(k) (G) and study the facial structure of the corresponding polytope P-k (G). We show facets that Pk+1(G) inherits from P-k(G) and show how to lift facets from P-k (G) to Pk+l (G). We project facets of P-1 (G o K-k) into facets of P-k (G), where G o K-k is the lexicographic product of G by a clique with k vertices. In both cases, we can obtain facet-defining inequalities from many of those known for the 1-fold coloring polytope. We also derive facets of P-k (G) from facets of stable set polytopes of subgraphs of G. In addition, we present classes of facet-defining inequalities based on strongly chi(k)-critical webs and antiwebs, which extend and generalize known results for 1-fold coloring. We introduce this criticality concept and characterize the webs and antiwebs having such a property. (C) 2016 Elsevier B.V. All rights reserved.
机译:图G的k倍x着色是将至少{{,2,...,x}}组中的至少k种不同颜色分配给每个顶点,以便将任意两个相邻顶点分配为不相交的颜色。 G的第k个色数由chi(k)(G)表示,是最小的x,因此G允许进行k倍的x着色。我们提出一种整数线性规划公式(ILP)来确定chi(k)(G),并研究相应多位点P-k(G)的面部结构。我们展示了Pk + 1(G)继承自P-k(G)的方面,并展示了如何将方面从P-k(G)提升到Pk + 1(G)。我们将P-1(G o K-k)的面投影到P-k(G)的面中,其中G o K-k是G的词法乘积,带有k个顶点。在这两种情况下,我们都可以从许多已知的1倍着色多表位获得不平等的方面。我们还从G的子图的稳定集多边形的刻面衍生出Pk(G)的刻面。此外,我们基于强chi(k)临界网和反网提出了定义刻面的不等式类别,这些不等式扩展并概括了已知结果用于1色着色。我们介绍此临界概念并表征具有这种特性的纤维网和反纤维网。 (C)2016 Elsevier B.V.保留所有权利。

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