Organizers
The SUSTech Discrete Mathematics Seminar is organized by Ferdinand Ihringer, Caiheng Li, Qing Xiang, and Ziqing Xiang.
You can contact us under discretemath@sustech.edu.cn.
Talks
Recent Talks
Speaker: Yue Yang (National University of Singapore)
Room: College of Science M1001
Time: 2025/12/11, Thursday, 10:00 - 11:00
Tencent Meeting: 116 415 990
Halpern-Läuchli Theorem (HL) is one instance of Ram-seyan theorems, with deep connections to mathematical logic. In this talk, I will report some recent results related to HL, jointly obtained with Chitat Chong and Wei Li from National University of Singapore. I will also spend some time introducing Reverse Mathematics to the general audience, including some history, main motivation and basic terminologies.
Speaker: Shuchao Li (Central China Normal University)
Room: College of Science M1001
Time: 2025/12/04, Thursday, 10:00 - 11:00
Tencent Meeting: 654 651 904
Turán-type problem is a fundamental problem in extremal graph theory. The spectral Turán-type problem is a newly developed one in this field. Both of these two types of extremal problems attract more and more researchers’ attention. In this talk, we first introduce the background in this field. Then we present our new results on (non-) color critical graphs along this line. Finally, we propose some further research issues in this field.
Speaker: Weicong Li (Great Bay University)
Room: College of Science M4009
Time: 2025/11/27, Thursday, 10:00 - 11:00
Tencent Meeting: 111 643 003
In this talk, I will present the complete classification of triply-transitive strongly regular graphs. This work concludes a program initiated by Herman, Maleki, and Razafimahatratra, who resolved most cases but left open the status of two infinite families from finite geometry. We prove that these remaining families are indeed triply-transitive, thereby settling the classificaition. This is joint work with Hanlin Zou.
Speaker: Jack Koolen (University of Science and Technology of China)
Room: College of Science M4009
Time: 2025/11/25, Tuesday, 10:00 - 11:00
Tencent Meeting: 868 415 472
In 1979, Neumaier gave a bound on λ in terms of m and μ, where -m is the smallest eigenvalue of a primitive strongly regular graph, unless the graph in question belongs to one of the two infinite families of strongly regular graphs. We improve this result. We also indicate how our methods can be used to give an alternate derivation of Bruck’s Completion Theorem for orthogonal arrays.
Speaker: Tatsuro Ito (Anhui University)
Room: College of Science M4009
Time: 2025/11/25, Tuesday, 11:00 - 12:00
Tencent Meeting: 868 415 472
Last year, I gave a talk at SUSTECH with the same title, in which I made two conjectures. This is a continuation of the talk. It turns out that one of them is correct and the other is wrong.
I will discuss the coherent configuration that arises from the action of a maximal parabolic subgroup H of GL(N,q) acting on the set of all subspaces ̃X of F_q^N. The 1st and 2nd eigenmatrices of the association scheme on each fibre are explictly given in terms of those of q-Johnson schemes and bilinear forms schemes. I will explain the structure of the Bose-Mesner algebra of the association scheme in terms of group characters, and how it is globally connected to others in the coherent configuration.
This is joint work with Xiaoye Liang.
