Monday, October 7, 2024

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2024-10-10 / 15:30 ~ 16:30
학과 세미나/콜로퀴엄 - 대수기하학: 인쇄
by ()
I will explain the notion of projection of syzygies, which was originally given by Ehbauer and later was much used by many mathematicians and then give two applications of it. We will firstly explain how it can be used to study the syzygies of canonical curves and in particular explain its application to a conjecture by Schreyer on the ranks of generating linear syzygies for general canonical curves. We will then explain an application of it to the study of linear syzygies of Veronese varieties.
2024-10-10 / 14:00 ~ 15:00
학과 세미나/콜로퀴엄 - 대수기하학: 인쇄
by 한강진()
In this talk, we report some results on equations and the ideal of $\sigma_k(v_d(\mathbb{P}^n))$, the $k$-th secant variety of $d$-uple Veronese embedding of a projective space, in case of the $k$-th secant having a relatively small degree. Knowledge on defining equations of higher secant varieties is fundamental in the study of algebraic geometry and in recent years it also has drawn a strong attention in relation to tensor rank problems. We first recall known results on the equation of a $k$-th secant variety and introduce key notions for this work, which are '$k$-secant variety of minimal degree' and 'del Pezzo $k$-secant variety', due to Ciliberto-Russo and Choe-Kwak, respectively. Next, we focus on the case of $\sigma_4(v_3(\mathbb{P}^3))$ in $\mathbb{P}^{19}$ as explaining our method and considering its consequences. We present more results which can be obtained by the same method. This is a joint work with K. Furukawa (Josai Univ.).
2024-10-10 / 10:30 ~ 11:30
학과 세미나/콜로퀴엄 - 대수기하학: 인쇄
by ()
We use the geometry of symmetric products of curves to construct rank one symmetric Ulrich sheaves on the (higher) secant varieties. Time permitting, we will also give an application towards an algebraic theory of knots. This is joint work with M. Kummer and J. Park.
2024-10-10 / 14:30 ~ 15:30
학과 세미나/콜로퀴엄 - 정수론: 인쇄
by 박철()
It is believed that one can attach a smooth mod-p representation of a general linear group to a mod-p local Galois representation in a natural way that is called mod-p Langlands program. This conjecture is quite far from being understood beyond GL₂(ℚₚ). However, for a given mod-p local Galois representation one can construct a candidate on the automorphic side corresponding to the Galois representation for mod-p Langlands correspondence via global Langlands. In this talk, we introduce automorphic invariants on the candidate that determine the given Galois representation for a certain family of mod-p Galois representations.
2024-10-11 / 13:30 ~ 14:30
학과 세미나/콜로퀴엄 - Topology, Geometry, and Data Analysis: 인쇄
by ()
In this talk, I will first review the story about single/multi-parameter persistent homology and its algebraic abstraction, persistence modules, from the perspective of representation theory. Then, I will define the so-called interval rank invariant of persistence modules. This invariant can be computed easily by utilizing our proposed formula though its definition is purely algebraic, which will become the main part of this talk. One direct application of the formula is to show the relation between our invariant and the generalized rank invariant proposed by Kim-Memoli. If time permits, I will introduce some other applications and related content.
2024-10-07 / 16:30 ~ 18:00
학과 세미나/콜로퀴엄 - 대수기하학: 인쇄
by 최도영(KAIST)
We present a formula for the degree of the 3-secant variety of a nonsingular projective variety embedded by a 5-very ample line bundle. The formula is provided in terms of Segre classes of the tangent bundle of a given variety. We use the generalized version of double point formula to reduce the calculation into the case of the 2-secant variety. Due to the singularity of the 2-secant variety, we use secant bundle as a nonsingular birational model and compute multiplications of desired algebraic cycles. Additionally, we compute the Hilbert-Samuel multiplicity of 2-secant variety along given variety.
2024-10-10 / 11:50 ~ 12:40
대학원생 세미나 - 대학원생 세미나: 인쇄
by 이도현()
TBA
2024-10-14 / 16:00 ~ 17:00
편미분방정식 통합연구실 세미나 - 편미분방정식: Null shell solutions - stability and instability 인쇄
by (고등과학원)
In this talk, we study initial value problem for the Einstein equation with null matter fields, motivated by null shell solutions of Einstein equation. In particular, we show that null shell solutions can be constructed as limits of spacetimes with null matter fields. We also study the stability of these solutions in Sobolev space: we prove that solutions with one family of null matter field are stable, while the interaction of two families of null matter fields can give rise to an instability.
2024-10-08 / 16:00 ~ 17:00
SAARC 세미나 - SAARC 세미나: 인쇄
by 손영탁()
Modern machine learning methods such as multi-layer neural networks often have millions of parameters achieving near-zero training errors. Nevertheless, they maintain strong generalization capabilities, challenging traditional statistical theories based on the uniform law of large numbers. Motivated by this phenomenon, we consider high-dimensional binary classification with linearly separable data. For Gaussian covariates, we characterize linear classification problems for which the minimum norm interpolating prediction rule, namely the max-margin classification, has near-optimal generalization error. In the second part of the talk, we consider max-margin classification with non-Gaussian covariates. In particular, we leverage universality arguments to characterize the generalization error of non-linear random features model, a two-layer neural network with random first layer weights. In the wide-network limit, where the number of neurons tends to infinity, we show how non-linear max-margin classification with random features collapse to a linear classifier with a soft-margin objective.
2024-10-10 / 16:15 ~ 17:15
학과 세미나/콜로퀴엄 - 콜로퀴엄: 인쇄
by 김대욱(KAIST 뇌인지과학과)
In this talk, I will take you on a journey from mathematical concepts to their applications in brain and cognitive sciences. We will explore how differential equations and nonlinear dynamical systems can be employed to model complex biological systems, including the brain. I will also discuss how these models help in understanding higher-level processes such as sleep and circadian rhythms, offering a deeper glimpse into how the brain operates as a complex, dynamic system. Additionally, I will share my personal journey from my student days to my current role as a professor in brain and cognitive sciences, illustrating how my research path has evolved over time.
2024-10-08 / 16:30 ~ 17:30
IBS-KAIST 세미나 - 이산수학: Canonical colourings in random graphs 인쇄
by Mathias Schacht(University of Hamburg)
Rödl and Ruciński established Ramsey’s theorem for random graphs. In particular, for fixed integers $r$, $\ell\geq 2$ they showed that $n^{-\frac{2}{\ell+1}}$ is a threshold for the Ramsey property that every $r$-colouring of the edges of the binomial random graph $G(n,p)$ yields a monochromatic copy of $K_\ell$. We investigate how this result extends to arbitrary colourings of $G(n,p)$ with an unbounded number of colours. In this situation Erdős and Rado showed that canonically coloured copies of $K_\ell$ can be ensured in the deterministic setting. We transfer the Erdős-Rado theorem to the random environment and show that for $\ell\geq 4$ both thresholds coincide. As a consequence the proof yields $K_{\ell+1}$-free graphs $G$ for which every edge colouring yields a canonically coloured $K_\ell$. This is joint work with Nina Kamčev.
Events for the 취소된 행사 포함 모두인쇄
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