Half-Simple Symmetric Venn Diagrams

Chip Killian, Department of Computer Science, Duke University, USA.
Frank Ruskey, Department of Computer Science, University of Victoria, Canada.
Carla Savage, Department of Computer Science, North Carolina State University, USA.
Mark Weston, Department of Computer Science, University of Victoria, Canada.

Abstract:

A Venn diagram is simple if at most two curves intersect at any given point. A recent paper of Griggs, Killian, and Savage [Elec. J. Combinatorics, 11 (2004) #R2] shows how to construct rotationally symmetric Venn diagrams for any prime number of curves. However, the resulting diagrams contain only C(n,n/2) intersection points, whereas a simple Venn diagram contains 2n-2 intersection points. We show how to modify their construction to give symmetric Venn diagrams with asymptotically at least 2n-1 intersection points, whence the name "half-simple".



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