A Density Turán Theorem

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985807%3A_____%2F17%3A00474851" target="_blank" >RIV/67985807:_____/17:00474851 - isvavai.cz</a>

Výsledek na webu

<a href="http://dx.doi.org/10.1002/jgt.22075" target="_blank" >http://dx.doi.org/10.1002/jgt.22075</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1002/jgt.22075" target="_blank" >10.1002/jgt.22075</a>

Jazyk výsledku

angličtina

Název v původním jazyce

A Density Turán Theorem

Popis výsledku v původním jazyce

Let F be a graph that contains an edge whose deletion reduces its chromatic number. For such a graph F, a classical result of Simonovits from 1966 shows that every graph on n > n(0)(F) vertices with more than chi(F)-2/chi(F)-1. n(2)/2 edges contains a copy of F. In this article we derive a similar theorem for multipartite graphs. For a graph H and an integer l >= v(H), let d(l) (H) be the minimum real number such that every l-partite graph whose edge density between any two parts is greater than d(l)(H) contains a copy of H. Our main contribution in this article is to show that d(l) (H) = chi(H)-2/chi(H)-1 for all l >= l(0)(H) sufficiently large if and only if H admits a vertex-coloring with chi(H) - 1 colors such that all color classes but one are independent sets, and the exceptional class induces just a matching. When H is a complete graph, this recovers a result of Pfender (Combinatorica 32 (2012), 483-495). We also consider several extensions of Pfender's result.

Název v anglickém jazyce

A Density Turán Theorem

Popis výsledku anglicky

Let F be a graph that contains an edge whose deletion reduces its chromatic number. For such a graph F, a classical result of Simonovits from 1966 shows that every graph on n > n(0)(F) vertices with more than chi(F)-2/chi(F)-1. n(2)/2 edges contains a copy of F. In this article we derive a similar theorem for multipartite graphs. For a graph H and an integer l >= v(H), let d(l) (H) be the minimum real number such that every l-partite graph whose edge density between any two parts is greater than d(l)(H) contains a copy of H. Our main contribution in this article is to show that d(l) (H) = chi(H)-2/chi(H)-1 for all l >= l(0)(H) sufficiently large if and only if H admits a vertex-coloring with chi(H) - 1 colors such that all color classes but one are independent sets, and the exceptional class induces just a matching. When H is a complete graph, this recovers a result of Pfender (Combinatorica 32 (2012), 483-495). We also consider several extensions of Pfender's result.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10101 - Pure mathematics

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2017

Kód důvěrnosti údajů

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

Název periodika

Journal of Graph Theory

ISSN

0364-9024

e-ISSN

—

Svazek periodika

85

Číslo periodika v rámci svazku

2

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

29

Strana od-do

496-524

Kód UT WoS článku

000402151300014

EID výsledku v databázi Scopus

2-s2.0-85018815115