A new methodology in Geometric Transversal Theory

Seminar: 
Geometry, Symmetry and Physics
Event time: 
Thursday, January 27, 2005 - 9:30am to Wednesday, January 26, 2005 - 7:00pm
Location: 
205 LOM
Speaker: 
Ricky Pollack
Speaker affiliation: 
Courant Institute
Event description: 

We (in joint work with J. E. Goodman) describe a new encoding of a family of mutually disjoint compact convex sets that captures many of its combinatorial properties and use it to give a new proof of the Edelsbrunner-Sharir theorem that a collection of $n$ mutually disjoint compact convex sets in the plane cannot be met by straight lines in more than $2n-2$ combinatorially distinct ways. The encoding generalizes our encoding of planar point configurations by “allowable sequences” of permutations. Since it applies as well to a collection of compact connected sets with a specified pseudoline arrangement $\cal A$ of separators and double tangents the result extends the Edelsbrunner-Sharir theorem to the case of geometric permutations induced by pseudoline transversals compatible with $\cal A$.

Special note: 
Special Combinatorics & Geometry seminar