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

Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar (in cooperation with A. Steger, D. Steurer and B. Sudakov)

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

Interlacing adjoints on directed graphs

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