Restricted frame graphs and a conjecture of Scott

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F16%3A10333128" target="_blank" >RIV/00216208:11320/16:10333128 - isvavai.cz</a>

Výsledek na webu

<a href="http://www.combinatorics.org/ojs/index.php/eljc/article/view/v23i1p30" target="_blank" >http://www.combinatorics.org/ojs/index.php/eljc/article/view/v23i1p30</a>

DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

Restricted frame graphs and a conjecture of Scott

Popis výsledku v původním jazyce

Scott proved in 1997 that for any tree T, every graph with bounded clique number which does not contain any subdivision of T as an induced subgraph has bounded chromatic number. Scott also conjectured that the same should hold if T is replaced by any graph H. Pawlik et al. recently constructed a family of triangle free intersection graphs of segments in the plane with unbounded chromatic number (thereby disproving an old conjecture of Erdos). This shows that Scott's conjecture is false whenever H is obtained from a non-planar graph by subdividing every edge at least once. It remains interesting to decide which graphs H satisfy Scott's conjecture and which do not. In this paper, we study the construction of Pawlik et al. in more details to extract more counterexamples to Scott's conjecture. For example, we show that Scott's conjecture is false for any graph obtained from K-4 by subdividing every edge at least once. We also prove that if G is a 2-connected multigraph with no vertex contained in every cycle of G, then any graph obtained from G by subdividing every edge at least twice is a counterexample to Scott's conjecture.

Název v anglickém jazyce

Restricted frame graphs and a conjecture of Scott

Popis výsledku anglicky

Scott proved in 1997 that for any tree T, every graph with bounded clique number which does not contain any subdivision of T as an induced subgraph has bounded chromatic number. Scott also conjectured that the same should hold if T is replaced by any graph H. Pawlik et al. recently constructed a family of triangle free intersection graphs of segments in the plane with unbounded chromatic number (thereby disproving an old conjecture of Erdos). This shows that Scott's conjecture is false whenever H is obtained from a non-planar graph by subdividing every edge at least once. It remains interesting to decide which graphs H satisfy Scott's conjecture and which do not. In this paper, we study the construction of Pawlik et al. in more details to extract more counterexamples to Scott's conjecture. For example, we show that Scott's conjecture is false for any graph obtained from K-4 by subdividing every edge at least once. We also prove that if G is a 2-connected multigraph with no vertex contained in every cycle of G, then any graph obtained from G by subdividing every edge at least twice is a counterexample to Scott's conjecture.

Druh

J_x - Nezařazeno - Článek v odborném periodiku (Jimp, Jsc a Jost)

CEP obor

IN - Informatika

OECD FORD obor

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Projekt

<a href="/cs/project/LL1201" target="_blank" >LL1201: Komplexní Struktury: Regularita v Kombinatorice a Diskrétní Matematice</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2016

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Electronic Journal of Combinatorics

ISSN

1077-8926

e-ISSN

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Svazek periodika

23

Číslo periodika v rámci svazku

1

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

21

Strana od-do

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Kód UT WoS článku

000382632700001

EID výsledku v databázi Scopus

2-s2.0-84958824979