Department of Computer Science | Institute of Theoretical Computer Science | CADMO

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar Talk Information |

**Date and Time**: Tuesday, June 09, 2009, 12:15 pm

**Duration**: This information is not available in the database

**Location**: OAT S15/S16/S17

**Speaker**: Jan Foniok

A theorem attributed to Hasse, Gallai, Roy and/or Vitaver claims that every orientation of every non-k-colourable graph contains a long directed path or a directed cycle (so it contains a homomorphic image of a long directed path), where "long" means "with at least k+1 vertices". We extend this theorem and prove that there is a family P of oriented paths with unbounded algebraic height such that every orientation of every non-4-colourable graph contains a homomorphic image of every path in P. (algebraic height = #forward arcs - #backward arcs) The motivation for this work is Hedetniemi's product- colouring conjecture (but probably I will not have time to discuss it); the method is "adjoint functors" (and I certainly want to discuss that).

Joint work with J. Nešetřil and C. Tardif.

Upcoming talks | All previous talks | Talks by speaker | Upcoming talks in iCal format (beta version!)

Previous talks by year: 2024 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996

Information for students and suggested topics for student talks

Automatic MiSe System Software Version 1.4803M | admin login