Tuesday, October 8, 2024

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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.
2024-10-10 / 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.
2024-10-15 / 16:00 ~ 17:00
SAARC 세미나 - SAARC 세미나: 인쇄
by 라준현(KIAS)
Wave turbulence refers to the statistical theory of weakly nonlinear dispersive waves. In the weakly turbulent regime of a system of dispersive waves, its statistics can be described via a coarse-grained dynamics, governed by the kinetic wave equation. Remarkably, kinetic wave equations admit exact power-law solutions, called Kolmogorov-Zakharov spectra, which resemble Kolmogorov spectrum of hydrodynamic turbulence, and is often interpreted as a transient equilibrium between excitation and dissipation. In this talk, we will outline a local well-posedness result for kinetic wave equation for a toy model for wave turbulence. The result includes well-posedness near K-Z spectra, and demonstrates a surprising smoothing effect of the kinetic wave equation. The talk is based on the joint work with Pierre Germain (ICL) and Katherine Zhiyuan Zhang (Northeastern).
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)

2024-10-15 / 10:30 ~ 11:30
학과 세미나/콜로퀴엄 - 대수기하학: 인쇄
by ()
The lecture series gives a view on computational methods and their some applications to existence and classfication problems. In the first lectures I will introduce Groebner basis and their basic applications in commutative algebra such as computing kernel and images of morphism between finitely presented modules over polynomial rings. As a theoretical application of Groebner basis I will give Petri's analysis of the equations of a canonical curve. The second topic will be Computer aided existence and unirationality proofs of algebraic varieties and their moduli spaces. In case of curves liaison theory is needed, which will be developed. For existence proofs random searches over finite fields is a technique that has not been exploited very much. I will illustrate this technique in a number of examples, in particular for the construction of certain surfaces. Classification of non-minimal surfaces uses adjunction theory. We will discuss this from a computational point of view.
2024-10-15 / 16:30 ~ 17:30
IBS-KAIST 세미나 - 이산수학: Random walks on percolation 인쇄
by Kyeongsik Nam(KAIST)
In general, random walks on fractal graphs are expected to exhibit anomalous behaviors, for example heat kernel is significantly different from that in the case of lattices. Alexander and Orbach in 1982 conjectured that random walks on critical percolation, a prominent example of fractal graphs, exhibit mean field behavior; for instance, its spectral dimension is 4/3. In this talk, I will talk about this conjecture for a canonical dependent percolation model.
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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