Event

Sami Douba, McGill University

Wednesday, February 27, 2019 15:00to16:00
Burnside Hall Room 920, 805 rue Sherbrooke Ouest, Montreal, QC, H3A 0B9, CA

Title:2-Systems of arcs on spheres with prescribed endpoints.

Abstract: A 2-system of arcs on an n-punctured sphere S is a collection of (homotopy classes of) simple arcs on S joining punctures and pairwise intersecting at most twice. Bar-Natan proved that a 2-system of arcs on S beginning and ending at a fixed puncture has size at most n choose 3. In this talk, I will sketch a proof that the same holds for a 2-system of arcs on S joining a fixed pair of distinct punctures.

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