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

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar Talk Information |

**Date and Time**: Thursday, January 10, 2013, 12:15 pm

**Duration**: 30 minutes

**Location**: CAB G51

**Speaker**: Jan Foniok (Queen's University)

**Theorem (Geller, Stahl):** Let *G* be a graph. Then the lexicographic product *G*[*K*_{2}] is *n*-colourable if and only if *G* admits a homomorphism to the Kneser graph *K*(*n*,2).

**Theorem (El-Zahar, Sauer):** For two graphs *G* and *H*, the categorial product *G* × *H* is *n*-colourable if and only if *G* admits a homomorphism to the exponential graph *K _{n}^{H}*.

What do these two theorems have in common? Each is an example of the same phenomenon, known in category theory as *adjoint functors*. I will explain what they are and show some other applications, such as a circular version of the Gallai–Roy (–Hasse–Vitaver) Theorem.

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

Previous talks by year: 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