マサリク大学の藤井 宗一郎先生の講演が下記の日程で行われます。
皆さま是非ともご参加ください。（申込不要）

日時：2025年2月7日（金）
　　　　　　　　15：00～17：00
場所：理学研究科３号館108室

タイトル：Hom complexes of graph homomorphisms and square-free graphs

概要：
The Hom complex Hom(G, H) is a certain polyhedral complex associated with a pair of
(undirected, finite, and simple) graphs G and H, whose vertices correspond to the graph homomorphisms from G to H. Hom complexes have been applied to the graph coloring problem, and are also related to the more recent topic of combinatorial reconfiguration.
In this talk, I will begin with the basics of Hom complexes and explain our recent result determining the homotopy type of (each connected component of) Hom(G, H) when H is square-free, meaning that it does not contain the 4-cycle graph as a subgraph. Although it is known that the homotopy type of Hom(G, H) can be quite complicated in general, for a connected G and a square-free H, we show that each connected component of Hom(G, H) is homotopy equivalent to a wedge sum of circles. A key tool for this is a certain “path object” construction for graphs, which might be of independent interest.(Based on joint work with Kei Kimura and Yuta Nozaki.)

・本学の学生は申込不要です。

・本講演は京都大学のスーパーグローバル教育プログラム、スーパーグローバルコース（数学分野）の企画講演です。当コースについての詳細はhttps://www.math.kyoto-u.ac.jp/ja/ktgu/ktgu　をご覧ください。