====== Pavle Blagojevic (University of Belgrade) ====== ====== How to Complicate a ``Simple'' Problem: Computational Topology of Equivariant Maps from Spheres to Complements of Arrangements ====== ===== Abstract for the Combinatorics and Number Theory and Geometry/Topology Seminars 2003 November 24 ===== The point of this talk is to illustrate the interplay of combinatorial and topological methods in combinatorial problems. I will consider a combinatorial problem (a 4-fan partition of 2 masses), its transformation into a topological problem on subspace arrangements, and the combinatorial and equivariant cohomology techniques in the solution of this problem.