# Noon lecture

list of noon lectures ( 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | future lectures)

On 21.02.2008 at 12:20 in S5, there is the following noon lecture:

# A new bound for a particular case of the Caccetta-Häggkvist conjecture

## Nicolas Lichiardopol

## Lycée Adam de Craponne, Salon, Francie

## Abstract

In a recent paper, Hamburger, Haxell and Kostochka have proved that if $\alpha \geq 0.35312$, then any digraph $D$ of order $n$ with minimum out-degree at least $\alpha n$, contains a directed cycle of length at most three. They have also proved that if $\beta \geq 0.34564$, then any digraph $D$ of order $n$ with both minimum out-degree and minimum in-degree at least $\beta n$, contains a directed cycle of length at most three. In my talk, by using the first result, I slightly improve the second bound. Namely, I prove that if $\beta \geq \frac{1}{2.9016}\approx 0.34464$, then any digraph $D$ of order $n$ with both minimum out-degree and minimum in-degree at least $\beta n$, contains a directed cycle of length at most three.

list of noon lectures ( 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | future lectures)

Webmaster: kamweb.mff.cuni.cz Modified: 19. 10. 2010