Events
DMS Combinatorics Seminar |
| Time: Feb 25, 2026 (01:00 PM) |
| Location: 328 Parker Hall |
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Details:
Speaker: Donggyu Kim, (Georgia Institute of Technology) Title: Pseudo-orientable ribbon graphs As consequences, we obtain the Matrix--Quasi-tree Theorem for pseudo-orientable ribbon graphs and the log-concavity on a sequence \(q_i\) counting quasi-trees of size \(2i-1\) or \(2i\). To prove the latter result, we generalize Stanley's log-concavity theorem for regular matroids to regular \(\Delta\)-matroids. Finally, we exhibit an infinite family of non-pseudo-orientable ribbon graphs that fail to satisfy log-concavity. This is joint work with Changxin Ding. |
