最小非色λ可选图

IF 1 3区 数学 Q2 MATHEMATICS
Jialu Zhu, Xuding Zhu
{"title":"最小非色λ可选图","authors":"Jialu Zhu,&nbsp;Xuding Zhu","doi":"10.1002/jgt.23267","DOIUrl":null,"url":null,"abstract":"<div>\n \n <p>For a multiset <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n \n <mo>=</mo>\n \n <mrow>\n <mo>{</mo>\n \n <mrow>\n <msub>\n <mi>k</mi>\n \n <mn>1</mn>\n </msub>\n \n <mo>,</mo>\n \n <msub>\n <mi>k</mi>\n \n <mn>2</mn>\n </msub>\n \n <mo>,</mo>\n \n <mo>…</mo>\n \n <mo>,</mo>\n \n <msub>\n <mi>k</mi>\n \n <mi>q</mi>\n </msub>\n </mrow>\n \n <mo>}</mo>\n </mrow>\n </mrow>\n </mrow>\n </semantics></math> of positive integers, let <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <msub>\n <mi>k</mi>\n \n <mi>λ</mi>\n </msub>\n \n <mo>=</mo>\n \n <msubsup>\n <mo>∑</mo>\n \n <mrow>\n <mi>i</mi>\n \n <mo>=</mo>\n \n <mn>1</mn>\n </mrow>\n \n <mi>q</mi>\n </msubsup>\n \n <msub>\n <mi>k</mi>\n \n <mi>i</mi>\n </msub>\n </mrow>\n </mrow>\n </semantics></math>. A <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>-list assignment of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n </semantics></math> is a list assignment <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>L</mi>\n </mrow>\n </mrow>\n </semantics></math> of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n </semantics></math> such that the colour set <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <msub>\n <mo>⋃</mo>\n \n <mrow>\n <mi>v</mi>\n \n <mo>∈</mo>\n \n <mi>V</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>G</mi>\n \n <mo>)</mo>\n </mrow>\n </mrow>\n </msub>\n \n <mi>L</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>v</mi>\n \n <mo>)</mo>\n </mrow>\n </mrow>\n </mrow>\n </semantics></math> can be partitioned into the disjoint union <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <msub>\n <mi>C</mi>\n \n <mn>1</mn>\n </msub>\n \n <mo>∪</mo>\n \n <msub>\n <mi>C</mi>\n \n <mn>2</mn>\n </msub>\n \n <mo>∪</mo>\n \n <mo>⋯</mo>\n \n <mo>∪</mo>\n \n <msub>\n <mi>C</mi>\n \n <mi>q</mi>\n </msub>\n </mrow>\n </mrow>\n </semantics></math> of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>q</mi>\n </mrow>\n </mrow>\n </semantics></math> sets so that for each <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>i</mi>\n </mrow>\n </mrow>\n </semantics></math> and each vertex <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>v</mi>\n </mrow>\n </mrow>\n </semantics></math> of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n </semantics></math>, <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mo>∣</mo>\n \n <mi>L</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>v</mi>\n \n <mo>)</mo>\n </mrow>\n \n <mo>∩</mo>\n \n <msub>\n <mi>C</mi>\n \n <mi>i</mi>\n </msub>\n \n <mo>∣</mo>\n \n <mo>=</mo>\n \n <msub>\n <mi>k</mi>\n \n <mi>i</mi>\n </msub>\n </mrow>\n </mrow>\n </semantics></math>. We say <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n </semantics></math> is <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>-choosable if <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n </semantics></math> is <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>L</mi>\n </mrow>\n </mrow>\n </semantics></math>-colourable for any <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>-list assignment <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>L</mi>\n </mrow>\n </mrow>\n </semantics></math> of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n </semantics></math>. The concept of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>-choosability puts <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>k</mi>\n </mrow>\n </mrow>\n </semantics></math>-colourability and <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>k</mi>\n </mrow>\n </mrow>\n </semantics></math>-choosability in a same framework: If <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n \n <mo>=</mo>\n \n <mrow>\n <mo>{</mo>\n \n <mi>k</mi>\n \n <mo>}</mo>\n </mrow>\n </mrow>\n </mrow>\n </semantics></math>, then <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>-choosability is equivalent to <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>k</mi>\n </mrow>\n </mrow>\n </semantics></math>-choosability; if <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math> consists of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>k</mi>\n </mrow>\n </mrow>\n </semantics></math> copies of 1, then <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>-choosability is equivalent to <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>k</mi>\n </mrow>\n </mrow>\n </semantics></math>-colourability. If <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n </semantics></math> is <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>-choosable, then <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n </semantics></math> is <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <msub>\n <mi>k</mi>\n \n <mi>λ</mi>\n </msub>\n </mrow>\n </mrow>\n </semantics></math>-colourable. On the other hand, there are <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <msub>\n <mi>k</mi>\n \n <mi>λ</mi>\n </msub>\n </mrow>\n </mrow>\n </semantics></math>-colourable graphs that are not <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>-choosable, provided that <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math> contains an integer larger than 1. Let <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>ϕ</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>λ</mi>\n \n <mo>)</mo>\n </mrow>\n </mrow>\n </mrow>\n </semantics></math> be the minimum number of vertices in a <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <msub>\n <mi>k</mi>\n \n <mi>λ</mi>\n </msub>\n </mrow>\n </mrow>\n </semantics></math>-colourable non-<span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>-choosable graph. This paper determines the value of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>ϕ</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>λ</mi>\n \n <mo>)</mo>\n </mrow>\n </mrow>\n </mrow>\n </semantics></math> for all <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>λ</mi>\n </mrow>\n </mrow>\n </semantics></math>.</p>\n </div>","PeriodicalId":16014,"journal":{"name":"Journal of Graph Theory","volume":"110 3","pages":"283-289"},"PeriodicalIF":1.0000,"publicationDate":"2025-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Minimum Non-Chromatic-\\n \\n \\n \\n λ\\n \\n \\n -Choosable Graphs\",\"authors\":\"Jialu Zhu,&nbsp;Xuding Zhu\",\"doi\":\"10.1002/jgt.23267\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div>\\n \\n <p>For a multiset <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n \\n <mo>=</mo>\\n \\n <mrow>\\n <mo>{</mo>\\n \\n <mrow>\\n <msub>\\n <mi>k</mi>\\n \\n <mn>1</mn>\\n </msub>\\n \\n <mo>,</mo>\\n \\n <msub>\\n <mi>k</mi>\\n \\n <mn>2</mn>\\n </msub>\\n \\n <mo>,</mo>\\n \\n <mo>…</mo>\\n \\n <mo>,</mo>\\n \\n <msub>\\n <mi>k</mi>\\n \\n <mi>q</mi>\\n </msub>\\n </mrow>\\n \\n <mo>}</mo>\\n </mrow>\\n </mrow>\\n </mrow>\\n </semantics></math> of positive integers, let <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <msub>\\n <mi>k</mi>\\n \\n <mi>λ</mi>\\n </msub>\\n \\n <mo>=</mo>\\n \\n <msubsup>\\n <mo>∑</mo>\\n \\n <mrow>\\n <mi>i</mi>\\n \\n <mo>=</mo>\\n \\n <mn>1</mn>\\n </mrow>\\n \\n <mi>q</mi>\\n </msubsup>\\n \\n <msub>\\n <mi>k</mi>\\n \\n <mi>i</mi>\\n </msub>\\n </mrow>\\n </mrow>\\n </semantics></math>. A <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-list assignment of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> is a list assignment <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>L</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> such that the colour set <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <msub>\\n <mo>⋃</mo>\\n \\n <mrow>\\n <mi>v</mi>\\n \\n <mo>∈</mo>\\n \\n <mi>V</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>G</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow>\\n </msub>\\n \\n <mi>L</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>v</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow>\\n </mrow>\\n </semantics></math> can be partitioned into the disjoint union <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <msub>\\n <mi>C</mi>\\n \\n <mn>1</mn>\\n </msub>\\n \\n <mo>∪</mo>\\n \\n <msub>\\n <mi>C</mi>\\n \\n <mn>2</mn>\\n </msub>\\n \\n <mo>∪</mo>\\n \\n <mo>⋯</mo>\\n \\n <mo>∪</mo>\\n \\n <msub>\\n <mi>C</mi>\\n \\n <mi>q</mi>\\n </msub>\\n </mrow>\\n </mrow>\\n </semantics></math> of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>q</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> sets so that for each <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>i</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> and each vertex <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>v</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>, <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mo>∣</mo>\\n \\n <mi>L</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>v</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n \\n <mo>∩</mo>\\n \\n <msub>\\n <mi>C</mi>\\n \\n <mi>i</mi>\\n </msub>\\n \\n <mo>∣</mo>\\n \\n <mo>=</mo>\\n \\n <msub>\\n <mi>k</mi>\\n \\n <mi>i</mi>\\n </msub>\\n </mrow>\\n </mrow>\\n </semantics></math>. We say <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> is <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-choosable if <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> is <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>L</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-colourable for any <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-list assignment <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>L</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>. The concept of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-choosability puts <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>k</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-colourability and <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>k</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-choosability in a same framework: If <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n \\n <mo>=</mo>\\n \\n <mrow>\\n <mo>{</mo>\\n \\n <mi>k</mi>\\n \\n <mo>}</mo>\\n </mrow>\\n </mrow>\\n </mrow>\\n </semantics></math>, then <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-choosability is equivalent to <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>k</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-choosability; if <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> consists of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>k</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> copies of 1, then <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-choosability is equivalent to <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>k</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-colourability. If <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> is <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-choosable, then <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> is <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <msub>\\n <mi>k</mi>\\n \\n <mi>λ</mi>\\n </msub>\\n </mrow>\\n </mrow>\\n </semantics></math>-colourable. On the other hand, there are <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <msub>\\n <mi>k</mi>\\n \\n <mi>λ</mi>\\n </msub>\\n </mrow>\\n </mrow>\\n </semantics></math>-colourable graphs that are not <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-choosable, provided that <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math> contains an integer larger than 1. Let <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>ϕ</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>λ</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow>\\n </mrow>\\n </semantics></math> be the minimum number of vertices in a <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <msub>\\n <mi>k</mi>\\n \\n <mi>λ</mi>\\n </msub>\\n </mrow>\\n </mrow>\\n </semantics></math>-colourable non-<span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>-choosable graph. This paper determines the value of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>ϕ</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>λ</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow>\\n </mrow>\\n </semantics></math> for all <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>λ</mi>\\n </mrow>\\n </mrow>\\n </semantics></math>.</p>\\n </div>\",\"PeriodicalId\":16014,\"journal\":{\"name\":\"Journal of Graph Theory\",\"volume\":\"110 3\",\"pages\":\"283-289\"},\"PeriodicalIF\":1.0000,\"publicationDate\":\"2025-06-15\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Graph Theory\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1002/jgt.23267\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Graph Theory","FirstCategoryId":"100","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/jgt.23267","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0

摘要

G的一个λ列表赋值是L的一个列表赋值G使得颜色集∈v (G) L (v)可以划分为不相交并c1∪c2∪⋯∪cq (q)对于每个i和每个顶点v (G)∣L (v)∩ci∣= k I。我们说G是λ可选的,如果G是L -可色对于任意λ -list赋值L (G) λ选择性的概念将k -可色性和k -可选择性放在同一个框架中:如果λ = {k},则λ -可选择性等价于k -可选择性;如果λ包含k个1的副本,那么λ -选择性就相当于k -显色性。如果G是λ可选的,那么G是k λ可着色的。另一方面,有k个λ可着色的图是不可λ选择的,假设λ包含一个大于1的整数。设φ (λ)为k中的最小顶点数λ可着色非λ可选图。本文确定了所有λ的φ (λ)的值。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Minimum Non-Chromatic- λ -Choosable Graphs

For a multiset λ = { k 1 , k 2 , , k q } of positive integers, let k λ = i = 1 q k i . A λ -list assignment of G is a list assignment L of G such that the colour set v V ( G ) L ( v ) can be partitioned into the disjoint union C 1 C 2 C q of q sets so that for each i and each vertex v of G , L ( v ) C i = k i . We say G is λ -choosable if G is L -colourable for any λ -list assignment L of G . The concept of λ -choosability puts k -colourability and k -choosability in a same framework: If λ = { k } , then λ -choosability is equivalent to k -choosability; if λ consists of k copies of 1, then λ -choosability is equivalent to k -colourability. If G is λ -choosable, then G is k λ -colourable. On the other hand, there are k λ -colourable graphs that are not λ -choosable, provided that λ contains an integer larger than 1. Let ϕ ( λ ) be the minimum number of vertices in a k λ -colourable non- λ -choosable graph. This paper determines the value of ϕ ( λ ) for all λ .

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来源期刊
Journal of Graph Theory
Journal of Graph Theory 数学-数学
CiteScore
1.60
自引率
22.20%
发文量
130
审稿时长
6-12 weeks
期刊介绍: The Journal of Graph Theory is devoted to a variety of topics in graph theory, such as structural results about graphs, graph algorithms with theoretical emphasis, and discrete optimization on graphs. The scope of the journal also includes related areas in combinatorics and the interaction of graph theory with other mathematical sciences. A subscription to the Journal of Graph Theory includes a subscription to the Journal of Combinatorial Designs .
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