Pseudo-Visibility Graphs

Bodhayan Roy Tata Institute of Fundamental Research School of Technology and Computer Science Homi Bhabha Road
Tuesday, 8 Mar 2011 (all day)
A-212 (STCS Seminar Room)
The notion of visibility graphs can be extended to that of pseudo-visibility graphs, where the edges between vertices do not necessarily remain straight line-segments. We discuss the construction of pseudo-visibility graphs which cannot be drawn on the plane as any valid visibility graph keeping the polygonal boundary unaltered, even though they satisfy all the necessary combinatorial conditions known for a graph to be a visibility graph. This proves that the necessary conditions are not sufficient ones.