Wednesday, December 11, 2024

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2024-12-12 / 13:30 ~ 14:30
학과 세미나/콜로퀴엄 - 정수론: 인쇄
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Title: On a polynomial basis for MZV’s in positive characteristic Abstract: We recall the notion of the stuffle algebra and review known results for this algebra in characteristic 0. Then, we construct a polynomial basis for the stuffle algebra over a field in positive characteristic. As an application, we determine the transcendence degree for multiple zeta values in positive characteristic for small weights. This is joint work with Nguyen Chu Gia Vuong and Pham Lan Huong
2024-12-12 / 10:45 ~ 11:45
학과 세미나/콜로퀴엄 - Topology, Geometry, and Data Analysis: 인쇄
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We present scEGOT, a comprehensive single-cell trajectory inference framework based on entropic Gaussian mixture optimal transport. The main advantage of scEGOT allows us to go back and forth between continuous and discrete problems, and it provides a versatile trajectory inference method including reconstructions of the underlying vector fields at a low computational cost. Applied to the human primordial germ cell-like cell (PGCLC) induction system, scEGOT identified the PGCLC progenitor population and bifurcation time of segregation. Our analysis shows TFAP2A is insufficient for identifying PGCLC progenitors, requiring NKX1-2.
2024-12-13 / 16:00 ~ 17:00
학과 세미나/콜로퀴엄 - 박사논문심사: 시지지, 카스텔누오보-멈포드 정칙성, 그리고 텐서 계수에 대한 몇 가지 연구 인쇄
by 한종인()

2024-12-13 / 11:00 ~ 12:00
학과 세미나/콜로퀴엄 - 응용 및 계산수학 세미나: 인쇄
by 이영규()
We present HINTS, a Hybrid, Iterative, Numerical, and Transferable Solver that combines Deep Operator Networks (DeepONet) with classical numerical methods to efficiently solve partial differential equations (PDEs). By leveraging the complementary strengths of DeepONet’s spectral bias for representing low-frequency components and relaxation or Krylov methods’ efficiency at resolving high-frequency modes, HINTS balances convergence rates across eigenmodes. The HINTS is highly flexible, supporting large-scale, multidimensional systems with arbitrary discretizations, computational domains, and boundary conditions, and can also serve as a preconditioner for Krylov methods. To demonstrate the effectiveness of HINTS, we present numerical experiments on parametric PDEs in both two and three dimensions.
2024-12-11 / 15:00 ~ 16:00
학과 세미나/콜로퀴엄 - 박사논문심사: 모듈러 형식의 주기다항식의 산술적 성질에 관하여 인쇄
by Hojin Kim()

2024-12-13 / 16:30 ~ 17:30
IBS-KAIST 세미나 - 이산수학: Phase transition of degenerate Turán problems in p-norms 인쇄
by Jun Gao(IBS 극단 조합 및 확률 그룹)
For a positive real number $p$, the $p$-norm $\|G\|_p$ of a graph $G$ is the sum of the $p$-th powers of all vertex degrees. We study the maximum $p$-norm $\mathrm{ex}_{p}(n,F)$ of $F$-free graphs on $n$ vertices, focusing on the case where $F$ is a bipartite graph. It is natural to conjecture that for every bipartite graph $F$, there exists a threshold $p_F$ such that for $p< p_{F}$, the order of $\mathrm{ex}_{p}(n,F)$ is governed by pseudorandom constructions, while for $p > p_{F}$, it is governed by star-like constructions. We determine the exact value of $p_{F}$, under a mild assumption on the growth rate of $\mathrm{ex}(n,F)$. Our results extend to $r$-uniform hypergraphs as well. We also prove a general upper bound that is tight up to a $\log n$ factor for $\mathrm{ex}_{p}(n,F)$ when $p = p_{F}$. We conjecture that this $\log n$ factor is unnecessary and prove this conjecture for several classes of well-studied bipartite graphs, including one-side degree-bounded graphs and families of short even cycles. This is a joint work with Xizhi Liu, Jie Ma and Oleg Pikhurko.
2024-12-17 / 16:30 ~ 17:30
IBS-KAIST 세미나 - 이산수학: Counting homomorphisms in antiferromagnetic graphs via Lorentzian polynomials 인쇄
by 이준경(연세대)
An edge-weighted graph $G$, possibly with loops, is said to be antiferromagnetic if it has nonnegative weights and at most one positive eigenvalue, counting multiplicities. The number of graph homomorphisms from a graph $H$ to an antiferromagnetic graph $G$ generalises various important parameters in graph theory, including the number of independent sets and proper vertex colourings. We obtain a number of new homomorphism inequalities for antiferromagnetic target graphs $G$. In particular, we prove that, for any antiferromagnetic $G$, $|\mathrm{Hom}(K_d, G)|^{1/d} ≤ |\mathrm{Hom}(K_{d,d} \setminus M, G)|^{1/(2d)}$ holds, where $K_{d,d} \setminus M$ denotes the complete bipartite graph $K_{d,d}$ minus a perfect matching $M$. This confirms a conjecture of Sah, Sawhney, Stoner and Zhao for complete graphs $K_d$. Our method uses the emerging theory of Lorentzian polynomials due to Brändén and Huh, which may be of independent interest. Joint work with Jaeseong Oh and Jaehyeon Seo.
2024-12-12 / 16:15 ~ 17:15
학과 세미나/콜로퀴엄 - 콜로퀴엄: 인쇄
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Topological data analysis (TDA) is an emerging concept in applied mathematics, by which we can characterize shapes of massive and complex data using topological methods. In particular, the persistent homology and persistence diagrams are nowadays applied to a wide variety of scientific and engineering problems. In this talk, I will survey our recent research on persistent homology from three interrelated perspectives; quiver representation theory, random topology, and applications on materials science. First, on the subject of quiver representation theory, I will talk about our recent challenges to develop a theory of multiparameter persistent homology on commutative ladders. By applying interval decompositions/approximations on multiparameter persistent homology (Asashiba et al, 2022) to our setting, I will introduce a new concept called connected persistence diagrams, which properly possess information of multiparameter persistence, and show some properties of connected persistence diagrams. Next, about random topology, I will show our recent results on limit theorems (law of large numbers, central limit theorem, and large deviation principles) of persistent Betti numbers and persistence diagrams defined on several stochastic models such as random cubical sets and random point processes in a Euclidean space. Furthermore, I will also explain a preliminary work on how random topology can contribute to understand the decomposition of multiparameter persistent homology discussed in the first part. Finally, about applications, I will explain our recent activity on materials TDA project. By applying several new mathematical tools introduced above, we can explicitly characterize significant geometric and topological hierarchical features embedded in the materials (glass, granular systems, iron ore sinters etc), which are practically important for controlling materials funct
2024-12-11 / 16:00 ~ 17:00
IBS-KAIST 세미나 - IBS-KAIST 세미나: 인쇄
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TBA
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