# 세미나 및 콜로퀴엄

구글 Calendar나 iPhone 등에서 구독하면 세미나 시작 전에 알림을 받을 수 있습니다.

The subject of p-adic differential equations was pioneered by Dwork in 1950’s, who investigated p-adic properties of solutions of a certain hypergeometric differential equation. This study of Dwork’s study led to extremely fascinating applications in number theory; especially, on elliptic curves and modular forms. The main goal of this colloquium talk is to explain the motivating example of the p-adic hypergeometric differential equation studied by Dwork and its link to the Legendre family of elliptic curves. If time permits, I’d like to discuss some generalization of Dwork’s study to families of abelian varieties and its potential applications.

We use circles on a sphere to illustrate important concepts in symplectic topology. We explain the difficulties encountered in higher dimensions and to what extent it can be overcome. Subsequently, we introduce the Fukaya category and connect the story to Khovanov homology.

Given any integers $s,t\geq 2$, we show there exists some $c=c(s,t)>0$ such that any $K_{s,t}$-free graph with average degree $d$ contains a subdivision of a clique with at least $cd^{\frac{1}{2}\frac{s}{s-1}}$ vertices. In particular, when $s=2$ this resolves in a strong sense the conjecture of Mader in 1999 that every $C_4$-free graph has a subdivision of a clique with order linear in the average degree of the original graph. In general, the widely conjectured asymptotic behaviour of the extremal density of $K_{s,t}$-free graphs suggests our result is tight up to the constant $c(s,t)$. This is joint work with Richard Montgomery.

To an abelian category A satisfying certain finiteness conditions, one can associate an algebra H_A (the Hall algebra of A) which encodes the structures of the space of extensions between objects in A. For a non-additive setting, Dyckerhoff and Kapranov introduced the notion of proto-exact categories, as a non-additive generalization of an exact category, which is shown to suffice for the construction of an associative Hall algebra. In this talk, I will discuss the category of matroids in this perspective.