Discrete Math Seminar: Petr Skoda and Sophie Burrill
- Date: 06/12/2012
- Time: 14:30
Simon Fraser University
Petr Škoda -- Title: Obstructions of connectivity 2 for embedding graphs into the torus
Sophie Burrill -- Title: Generating trees for partitions and permutations with no k-nestings
Petr Škoda Abstract:We study the obstructions (minor-minimal forbidden graphs) for orientable surfaces that have a 2-vertex cut. The building blocks of the obstructions are described. As a consequence, the complete list of 68 obstructions for the torus that have connectivity 2 is constructed.
Sophie Burrill Abstract: We describea generating tree approach to the enumeration and exhaustive generation of set partitions and permutations with no $k$-nestings. Unlike previous work in the literature using connections of these objects with Young tableaux and restricted lattice walks, our approach deals directly with partitions and permutations diagrams. We detail a generation algorithm that uses only labelsto describe these set partitions and permutations with no $k$-nestings, and provide explicit functional equations for the generating functions, with $k$ as a parameter, getting valuable series results.
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