Prof. Emo Welzl and Prof. Bernd Gärtner
|Mittagsseminar Talk Information|
Date and Time: Thursday, January 24, 2008, 12:15 pm
Duration: This information is not available in the database
Location: CAB G51
Speaker: Philipp Zumstein
A vertex k-coloring of a plane graph G is called polychromatic if in every face of G all k colors appear. Let p(G) be the maximum number k for which there is a polychromatic k-coloring.
For a plane graph G, let g(G) denote the length of the shortest face in G. We show p(G) >= (3g(G)-5)/4 and on the other hand for each g there is a graph with g(G) = g and p(G) <= (3g+1)/4.
Furthermore, the problem of determining whether a plane graph admits a vertex coloring by 3 colors in which all colors appear in every face is NP-complete even for graphs in which all faces are of length 3 or 4 only. If all faces are of length 3 this can be decided in polynomial time.
The investigation of this problem is motivated by its connection to a variant of the art gallery problem in computational geometry.
Joint work with Noga Alon, Robert Berke, Kevin Buchin, Maike Buchin, Peter Csorba, Saswata Shannigrahi, and Bettina Speckmann.
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