主讲教师：许宝刚 人气：891 更新时间: 2015年10月20日
吴文俊数学重点实验室组合图论系列讲座之六十一【许宝刚】 摘要： We show that if a graph $G$ has neither triangles nor quadrilaterals, and has no odd holes of lengthat least 7, then $chi(G)le 4$ and $chi(G)le 3$ if $G$ has radius at most $3$, and for each vertex$u$ of $G$, the set of vertices of the same distance to $u$ induces a bipartite subgraph. This answers some questions of Plummer and Zha. Joint work with Gexin Yu and Xiaoya Zha.
主讲教师：张继平 人气：756 更新时间: 2016年05月25日
摘要：Adequacy of subgroups is very important in generalizations of Taylor-Wiles method for proving the automorphy of Galois representations. I will talk about some new progress on linear groups and the application related to adequacy of subgroups.
主讲教师：郁星星 人气：688 更新时间: 2016年05月25日
A subdivision of a graph G is denoted T G. Mader conjectured that every C4-free graph with average degree d contains TK_l with l = ?(d). Koml′os and Szemer′edi reduced this problem to expanders and proved Mader’s conjecture for n-vertex expanders with average degree d < exp(log1/8 n). We show that Mader's conjecture is true for n-vertex expanders with average degree d < n3/10, which improves Koml′os and Szemer′edi’s bound to a polynomial bound. As a consequence, we show that every C4-free graph with average degree d contains a TK_l with l = ?(d/(log d) c ) for any c > 3/2. This is joint work with H. Huang and Y. Wang
主讲教师：傅翔 人气：2633 更新时间: 2015年03月22日
Dominance is a useful partial ordering defined on the root systems of Coxeter groups. In the literature it has non-trivial applications in the group-theoretic, combinatorial and computational aspects of Coxeter groups. In this talk we outline a number of recent results on dominance. In particular, we discuss how dominance can be used to better understand the asymptotic behaviours of the so-called normalized roots of infinite Coxeter groups. Furthermore, we outline the natural interpretation of dominance in terms of the Cayley graphs of Coxeter groups. Time permitting, we may outline the connection between the visual boundaries of the Davis complexes of Coxeter groups and the limits of the so-called normalized roots of Coxeter groups. This talk is based on some recent joint work with Dr. Lawrence Reeves.
主讲教师：Aleksandr Makhnev 人气：985 更新时间: 2014年12月07日
Let Γ be a distance regular cover of (k +1)-clique with λ = μ. If local subgraphs are strongly regular with parameters (v’, k’, λ’, μ’), then v’= k, k’= λ, and b1= k ? λ ? 1 = (r ? 1)μ, so k’= λ devides v’? 1. It is determined parameters of strongly regular graphs with at most 1000 vertices, which may be local subgraphs in distance regular cover of clique with λ = μ. It is classified arc-transitive distance regular cover of clique with λ = μ with local subgraphs, whose parametrs belongs to our list.
主讲教师：Naoto Yotsutani 人气：1400 更新时间: 2015年05月18日
吴文俊数学重点实验室微分几何与分析系列讲座八十三【四谷直仁】 题目: DOUBLING CONSTRUCTION OF COMPACT MANIFOLDS WITH SPECIAL HOLONOMY The aim of this talk is to give differential-geometric constructions of Calabi-Yau 3-folds, 4- folds and compact Spin(7)-manifolds. Ingredients in our constructions are (orbifold) admissible pairs (with antiholomorphic involution), which were dealt with by Kovalev in a series of his papers (2003, 2011, 2013). For our convenience, we shall mainly discuss the case of CY 3-folds. If time permitted, we also give a concrete example with this construction. This talk is based on a series of joint works with Mamoru Doi.
主讲教师：Anyue Chen 人气：3188 更新时间: 2015年03月22日
In this talk, I'll address some important topics, particularly the extinction properties and their asymptotic behaviour of the Interacting Branching Collision Process (IBCP), which consists of two strongly interacting components: an ordinary Markov branching process (MBP) and a collision branching process (CBP). After establishing some elegant necessary and sufficient conditions for existence and uniqueness of IBCP, the explicit expressions are then obtained for the extinction probabilities for the regular, critical-explosive and super-explosive cases. The subtle sub-explosive case will also be addressed. The associated expected hitting times are also investigated and revealed. Moreover, considering some of these exact explicit expressions are very complicated and thus we turn to investigate the asymptotic behaviour of these extremely complicated and divergent expressions for extinction probabilities. Surprisingly, we are able to show that the asymptotic behaviour follows an elegant and homogenous power law with an index quantity. We further show that this interesting and important index quantity takes a very simple and uniform form which could be interpreted as the "spectrum", ranging from minus infinity to positive infinity, of the interaction between the two components of the IBCP.
主讲教师：吴可 人气：1419 更新时间: 2015年05月21日
吴文俊实验室数学物理系列报告之四十六 【吴可】 报告题目：Heisenberg代数和Fermi代数的范畴化报告人：首都师范大学数学学院 吴可教授时间：2015.5.19 （星期二）下午4:30 地点：管理科研楼 1418 摘要：TBA
主讲教师：彭岳建 人气：582 更新时间: 2016年05月25日
摘要：A number α ∈ [0,1) is jump for r-uniform graphs if there exists a constant c > 0 such that for any family F of r-uniform graphs, if the Turán density of F is greater than α, then the Tur´ an density of F is at least α + c. A fundamental result in extremal graph theory due to Erd¨ os and Stone implies that every number in [0,1) is a jump for r = 2. Erd¨ os also showed that every number in [0,r!r r ) is a jump for r ≥ 3. Furthermore, Frankl and R¨ odl showed the existence of non-jumps for r ≥ 3. But there are still a lot of unknowns regarding jumps or non-jumps for hypergraphs. We give a survey on the known result.
主讲教师：王诗宬 人气：687 更新时间: 2016年12月02日
11-30吴文俊讲座【王诗宬 院士】 摘要: I will give a survey talk on the recent results (joint with Derbez, Liu and Sun) around the title