Tuesday, October 7, 2025

2025-10-13 / 16:00 ~ 17:30

by (아주대학교)

In this talk, we prove that the inviscid surface quasi-geostrophic (SQG) equation is strongly ill-posed in critical Sobolev spaces: there exists an initial data $H^2(\mathbb{R}^2)$ without any solutions in $L^{\infty}_tH^2$. Then, we introduce similar ill-posedness results for $\alpha$-SQG and two-dimensional incompressible Euler equations. This talk is based on joint works with In-Jee Jeong(SNU), Young-Pil Choi(Yonsei Univ.), Jinwook Jung(Hanyang Univ.), and Min Jun Jo(Duke Univ.).

2025-10-14 / 16:30 ~ 17:30

IBS-KAIST 세미나 - 이산수학: An improved lower bound on the number of edges in list critical graphs via DP coloring

by Ilkyoo Choi(Department of Mathematics, Hankuk University of Fo)

A graph $G$ is (list, DP) $k$-critical if the (list, DP) chromatic number is $k$ but for every proper subgraph $G’$ of $G$, the (list, DP) chromatic number of $G’$ is less than $k$. For $k\geq 4$, we show a bound on the minimum number of edges in a DP $k$-critical graph, and our bound is the first bound that is asymptotically better than the corresponding bound for proper $k$-critical graphs by Gallai from 1963. Our result also improves the best bound on the list chromatic number. This is joint work with Bradshaw, Kostochka, and Xu.

Events for the 취소된 행사 포함