论文标题

用于图形分区的catlin型定理避免了规定的子图

A Catlin-type Theorem for Graph Partitioning Avoiding Prescribed Subgraphs

论文作者

Rowshan, Yaser, Taherkhani, Ali

论文摘要

作为Brooks定理的扩展,Catlin于1979年表明,如果$ h $既不是奇数周期,也不是最高度$δ(h)$的完整图,则$ h $具有顶点$δ(h)$ - 颜色,以便其中一种颜色类是最大独立集。令$ g $为连接的订单图,至少$ 2 $。 a $ g $ -free $ k $ - 图$ h $的颜色是$ h $的顶点$ h $的分区,$ v_1,\ ldots,v_k $,以至于$ h [v_i] $,$ h [v_i] $,对$ v_i $诱导的子级,不包含任何子图与$ g $ g $。作为对Catlin定理的概括,我们表明,图$ h $具有$ g $ - free $ \ lceil {δ(h)\ fovue uccon $ g $ - free子集的$ v(h)$,如果$ v(h)$ $ v(h)$,则$ v(g)} \ rceil $ - 如果$ v(h)$ h $满足以下条件; (1)$ h $如果$ g $是常规的,(2)$ h $不是$ k_ {kΔ(g)+1} $如果$ g \ simeq k_ {Δ(g)+1} $ g \ s+g $ g $ g $ isomorphic comorphic,则不是同构的。实际上,我们通过证明$ g_1,\ ldots,g_k $的图形是最低度的$ d_1,\ ldots,d_k $,并且$Δ(h)= \ sum_ {i = 1}^{k} d_k $,然后是$ h $ h $ h $ h, that each $H[V_i]$ is $G_i$-free and moreover one of $V_i$s can be chosen in a way that $H[V_i]$ is a maximum $G_i$-free subset of $V(H)$ except either $k=1$ and $H$ is isomorphic to $G_1$, each $G_i$ is isomorphic to $K_{d_i+1}$ and $ h $不是同构至$ k_ {δ(h)+1} $,或者每个$ g_i $都是同构为$ k_ {2} $,而$ h $不是一个奇怪的周期。

As an extension of the Brooks theorem, Catlin in 1979 showed that if $H$ is neither an odd cycle nor a complete graph with maximum degree $Δ(H)$, then $H$ has a vertex $Δ(H)$-coloring such that one of the color classes is a maximum independent set. Let $G$ be a connected graph of order at least $2$. A $G$-free $k$-coloring of a graph $H$ is a partition of the vertex set of $H$ into $V_1,\ldots,V_k$ such that $H[V_i]$, the subgraph induced on $V_i$, does not contain any subgraph isomorphic to $G$. As a generalization of Catlin's theorem we show that a graph $H$ has a $G$-free $\lceil{Δ(H)\over δ(G)}\rceil$-coloring for which one of the color classes is a maximum $G$-free subset of $V(H)$ if $H$ satisfies the following conditions; (1) $H$ is not isomorphic to $G$ if $G$ is regular, (2) $H$ is not isomorphic to $K_{kδ(G)+1}$ if $G \simeq K_{δ(G)+1}$, and (3) $H$ is not an odd cycle if $G$ is isomorphic to $K_2$. Indeed, we show even more, by proving that if $G_1,\ldots,G_k$ are connected graphs with minimum degrees $d_1,\ldots,d_k$, respectively, and $Δ(H)=\sum_{i=1}^{k}d_k$, then there is a partition of vertices of $H$ to $V_1,\ldots,V_k$ such that each $H[V_i]$ is $G_i$-free and moreover one of $V_i$s can be chosen in a way that $H[V_i]$ is a maximum $G_i$-free subset of $V(H)$ except either $k=1$ and $H$ is isomorphic to $G_1$, each $G_i$ is isomorphic to $K_{d_i+1}$ and $H$ is not isomorphic to $K_{Δ(H)+1}$, or each $G_i$ is isomorphic to $K_{2}$ and $H$ is not an odd cycle.

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