세미나/포럼
[세미나/포럼] [2018.12.14.금] 수학과 위상조합세미나 개최 안내
- 세미나/포럼
- 교내
- 박수현
- 2018-12-04
안녕하세요. 아주대 위상조합 세미나를 아래와 같이 개최하고자 합니다.
많은 참여부탁드립니다.
연사 : Yandong Bai (Northwestern Polytechnical University, China)
일시 : 12월 14일 금요일 15:30 ~ 16:30
장소 : 팔달관 621호
제목 : Bipartitions of digraphs
초록 :
Stiebitz asked in 1995 the following question. For any two positive integers $s$ and $t$, does there exist a finite integer $f(s,t)$ such that every digraph with minimum outdegree at least $f(s,t)$ admits a bipartition $(A,B)$ such that $A$ induces a subdigraph with minimum outdegree at least $s$ and $B$ induces a subdigraph with minimum outdegree at least $t$? In this talk, we give an affirmative answer for tournaments, multipartite tournaments and digraphs with bounded maximum indegree. In particular, we show that for every $\varepsilon$ with $0<\varepsilon<1/2$, there exists an integer $\delta_{0}$ such that every tournament $T$ with minimum outdegree at least $\delta_{0}$ admits a bipartition $(A,B)$ satisfying that $-1\leqslant |A|-|B| \leqslant 1$ and each vertex of $T$ has at least $(1/2-\varepsilon)$ of its outneighbors in both $A$ and $B$.