セミナー

Fracture squares and separable algebras

2025年12月12日(金) 16:00 - 17:30

Luca Pol (Postdoctoral Researcher, Max Planck Institute for Mathematics in Bonn, Germany)

In this talk I will present a way to reconstruct a category from its subcategories of complete and local objects while retaining the symmetric monoidal structure. As an application of this machinery I will discuss how to calculate separable algebras in equivariant homotopy theory.

会場: via Zoom / 研究本館 3階 セミナー室(345-347)

イベント公式言語: 英語

Widespread conservation of genetic effect sizes between human groups across traits

2025年12月12日(金) 13:30 - 15:00

Simon Robert Myers (Professor, University of Oxford, UK)

Understanding genetic differences between populations is essential for avoiding confounding in genome-wide association studies and improving polygenic score (PGS) portability. We developed a statistical pipeline to infer fine-scale Ancestry Components and applied it to UK Biobank data. Ancestry Components identify population structure not captured by widely used principal components, improving stratification correction for geographically correlated traits. To estimate the similarity of genetic effect sizes between groups, we developed ANCHOR, which estimates changes in the predictive power of an existing PGS in distinct local ancestry segments. ANCHOR infers highly similar (estimated correlation 0.98 ± 0.07) effect sizes between UK Biobank participants of African and European ancestry for 47 of 53 quantitative phenotypes, suggesting that gene–environment and gene–gene interactions do not play major roles in poor cross-ancestry PGS transferability for these traits in the United Kingdom, and providing optimism that shared causal mutations operate similarly in different populations.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

From perturbations of operators to noncommutative condensers

2025年12月11日(木) 16:00 - 17:00

Dan Voiculescu (Professor, Department of Mathematics, University of California, Berkeley, USA)

A numerical invariant, the quasicentral modulus underlies the multivariable generalizations of the classical Weyl-von Neumann-Kuroda and Kato-Rosenblum theorems. There are also connections to the Kolmogorov-Sinai dynamical entropy. I will also point out some of the open problems. Recently a noncommutative analogy with condenser capacity in nonlinear potential theory is emerging, that provides a new perspective on the subject.

会場: via Zoom / 研究本館 3階 359号室

イベント公式言語: 英語

Self-organized mechano-chemical instabilities drive the emergence of tissue morphogenesis in digit organoids

2025年12月11日(木) 13:00 - 14:00

アントワーヌ・ディエズ (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 数学応用研究チーム 研究員)

Tissue morphogenesis is an emergent phenomenon: macroscopic structures cannot be predicted from a mere list of genes and cells. We examine here how digits arise from a spherical limb bud and present a framework linking microscopic cellular behavior to morphogenesis. To extract digit morphogenesis in vitro, we created a limb-mesenchyme organoid that breaks symmetry and forms digit-like cartilage. Analyzing cell behavior, iterating between experimental evidence and cellular-based models, shows that microscopic mechanisms like differential adhesion between distal and proximal autopod cells, chemotaxis toward Fgf8b, and biased traction can drive tissue-wide deformations by convergent extension that eventually lead to the formation of digit structures. Taking the continuum limit of these microscopic rules yields a modified Cahn–Hilliard equation, that is well known to describe fluid interfaces and so-called fingering instabilities, but that is shown here to recapitulate well organoid morphogenesis. Taken together, this work suggests that the emergence of “fingers” can be explained in a theoretical framework as a type of fingering instability.

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

Graph polynomials and quantum field theory

2025年12月9日(火) 15:00 - 17:00

Michael McBreen (Assistant Professor, Department of Mathematics, The Institute of Mathematical Sciences, The Chinese University of Hong Kong, Hong Kong)

The Tutte polynomial was introduced in the 1940s as a two-variable generalisation of the chromatic polynomial of a graph. It is the universal matroid invariant satisfying a deletion-contraction relation, and is the subject of much recent work. I will describe a geometric realisation of the Tutte polynomial via the cohomology of a symplectic dual pair of hypertoric varieties. The same construction associates an interesting two-variable polynomial to any pair of symplectically dual spaces, whose one-variable specialisations recover the respective Poincare polynomials. Joint work with Ben Davison.

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

Generative sampling with physics-informed kernels

2025年12月8日(月) 14:00 - 15:00

Renzo Kapust (Ph.D. Student, Institute for Theoretical Physics, University Heidelberg, Germany)

We construct a generative network for Monte-Carlo sampling in lattice field theories and beyond, for which the learning of layerwise propagation is done and optimised independently on each layer. The architecture uses physics-informed renormalisation group flows that provide access to the layerwise propagation step from one layer to the next in terms of a diffusion equation for the respective renormalisation group kernel through a given layer. Thus, it transforms the generative task into that of solving once the set of independent and linear differential equations for the kernels of the transformation. As these equations are analytically known, the kernels can be refined iteratively. This allows us to structurally tackle out-of-domain problems generally encountered in generative models and opens the path to further optimisation. We illustrate the practical feasibility of the architecture within simulations in scalar field theories.

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

Full exceptional collections on Fano threefolds and the braid group action

2025年12月5日(金) 16:00 - 17:30

Anya Nordskova (カブリ数物連携宇宙研究機構 (Kavli IPMU) Postdoctoral researcher)

The bounded derived category D^b(X) of coherent sheaves on an algebraic variety X is a powerful tool that encodes a wealth of information about X. In some cases D^b(X) admits a particularly nice description via so-called full exceptional collections, which allow one to view D^b(X) as being glued from the simplest building blocks, each equivalent to the derived category D^b(pt) of a point. In this situation the set of all full exceptional collections admits an action of the braid group. In 1993, Bondal and Polishchuk conjectured that this braid group action is always transitive. After a short historical overview I will sketch the idea behind the proof of Bondal-Polishchuk's conjecture in the case when X is a Fano threefold of Picard rank 1 (e.g. the projective space P^3). This is the first 3-dimensional case where the transitivity of the braid group action has been verified. The talk is based on joint work with Michel Van den Bergh.

会場: 研究本館 3階 セミナー室(345-347) (メイン会場) / via Zoom

イベント公式言語: 英語

About analytic continuation of quantum field theories in non-integer dimensions

2025年12月5日(金) 14:00 - 15:30

Slava Rychkov (Professor, Institut des hautes études scientifiques, France)

Analytic continuation in dimension has been used first as a way to regularize perturbative quantum field theory. But since the work of Wilson and Fisher, quantum field theory in d-dimension has been used more radically, to connect theories living say, in d=4, to theories in d=3 and d=2. Mathematically it's not fully clear what this means. I will give some thoughts about this subject, and I will describe some recent paradoxes which arise when one consider expansion of O(N) models around d=2, based on recent work with Fabiana De Cesare.

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

The Functional Renormalisation Group: From the physics of strongly correlated systems to generative models

2025年12月5日(金) 10:30 - 12:00

Jan Martin Pawlowski (Professor, Institute for Theoretical Physics, University of Heidelberg, Germany)

In the past decades, the functional renormalisation group (fRG) has matured into a comprehensive approach to strongly-correlated (non-perturbative) systems, covering quantitatively both universal and non-universal phenomena. The fRG also constitutes an ideal approach for unravelling structural aspects of quantum field theories. This is not only interesting for studies in mathematical physics, but also guides systematic diagrammatic expansion schemes. It is also used to set up novel statistical (lattice) approaches to non-perturbative phenomena. In the present talk I survey these advances and illustrate the progress with selected examples ranging from ultracold atoms, QCD and quantum gravity to novel generative architectures for lattice simulations and beyond.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

Quantum Information in Scattering: From Amplitude Poles to Entanglement Features

2025年12月4日(木) 14:00 - 16:00

蘇 俊文 (Postdoctoral Researcher, Department of Physics, Tsinghua University, Beijing, China)

Probing quantum entanglement in high-energy collisions has recently become a rapidly growing direction in particle physics, aiming to measure quantum correlations at the highest energy scales accessible to humans. A key question is how such entanglement relies on the analytic structure of scattering amplitudes. In this talk, I will show that the pole structure, associated with intermediate heavy particles, leads to distinctive entanglement features. When a heavy particle mediates inelastic scatterings with three or more final particles, the entanglement entropy between its decay products and the rest exhibits a universal dip as the energy increases, reflecting the limited information flow through on-shell heavy particles and signaling entanglement suppression in the heavy-particle-dominated regime. This reveals entanglement structures beyond the usual “area-law” behavior of 2-to-2 processes. Finally, I will comment on possible ways to probe these features experimentally through analyses of final-state phase-space distributions. This talk is based on JHEP 10 (2025) 003 [arXiv: 2507.03555].

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

Biological Background of Duplicated Sequence Evolution: A Focus on Gene Conversion

2025年12月4日(木) 13:00 - 14:00

大窪 健児 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 基礎科学特別研究員)

Duplicated sequences—such as gene families, tandem arrays, and segmental duplications—are common in many genomes. Their evolution is shaped by several biological processes, including mutation, recombination, duplication, deletion, and gene conversion. Among these, gene conversion is especially important because it can make nearby copies more similar, while leaving distant copies free to diverge. In this seminar, I will give a broad and accessible overview of the biological background related to duplicated sequences, with a particular focus on what is known about gene conversion. I will summarize well-established patterns such as its dependence on genomic distance, sequence similarity, and recombination context. These biological features are often studied separately, so organizing them in one place can help provide a clearer foundation. The goal of the talk is to outline the biological principles that motivate thinking about duplicated sequences in a more formal or quantitative way in the future. I will not discuss specific model details. Instead, this presentation will serve as background preparation for later theoretical work.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

Quantum Computing Journal Club #1

2025年12月2日(火) 10:00 - 12:00

Bring a recent paper on quantum computing for discussion. No need to prepare slides.

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

From phase reduction to hypergraphs: the higher-order dynamics of coupled phase oscillators

2025年11月27日(木) 13:00 - 14:00

リッカルド・ムオロ (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 基礎科学特別研究員)

Networks are powerful tools in the modeling of complex systems, but they do not always capture the right interactions when multiple units are involved simultaneously. Such many-body interactions are encoded by higher-order structures which can be thought as extensions of networks. Over the last years, higher-order networks have been the focus of great excitement, since this novel framework has enormous potential for applications. In this talk, I will give an overview of higher-order interactions and their effects on nonlinear dynamics. I will introduce the basics of dynamics on networks and its extension to the case of higher-order interactions. As examples of the effects on nonlinear dynamics, I will discuss the case of phase reduction for systems with higher-order interactions and show the effects on synchronization dynamics.

会場: セミナー室 (359号室) / via Zoom

イベント公式言語: 英語

Introduction to Game Theory #3

2025年11月27日(木) 11:00 - 12:00

村瀬 洋介 (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 数理社会科学チーム チームディレクター)

An introductory lecture on game theory to promote potential interdisciplinary collaborations. No prior knowledge is required — the lecture is intended for non-experts. We will cover the fundamental concepts to help you build an intuitive understanding of how game theory analyzes strategic interactions. After briefly reviewing the previous lectures, we will talk about repeated games, where players are engaged in games repeatedly.

会場: via Zoom (メイン会場) / セミナー室 (359号室)

イベント公式言語: 英語

Hamiltonian Learning and Dynamics Prediction via Machine Learning

2025年11月26日(水) 15:00 - 16:00

李 可仁 (Assistant Professor, College of Physics and Optoelectronic Engineering, Shenzhen University, China)

Accurate prediction of quantum Hamiltonian dynamics and identification of Hamiltonian parameters are crucial for advancements in quantum simulations, error correction, and control protocols. This talk introduces a machine learning model with dual capabilities: it can deduce time-dependent Hamiltonian parameters from observed changes in local observables within quantum many-body systems, and it can predict the evolution of these observables based on Hamiltonian parameters. The model’s validity was confirmed through theoretical simulations across various scenarios and further validated by two experiments. Initially, the model was applied to a Nuclear Magnetic Resonance quantum computer, where it accurately predicted the dynamics of local observables. The model was then tested on a superconducting quantum computer with initially unknown Hamiltonian parameters, successfully inferring them. We believe that machine learning techniques hold great promise for enhancing a wide range of quantum computing tasks, including parameter estimation, noise characterization, feedback control, and quantum control optimization.

会場: via Zoom

イベント公式言語: 英語

Adaptive navigation strategies in adversarial predator-prey contexts

2025年11月20日(木) 13:00 - 14:00

西海 望 (新潟大学 教育研究院 自然科学系 特任准教授)

Animal navigation has long been a central topic in behavioral biology. In predator-prey systems, both predators and prey must navigate strategically - predators to capture prey and prey to reach safety - each evolving to outsmart the other through coevolution. To uncover the essence of these navigation strategies, I have investigated behavioral mechanisms across taxa. In bats, my collaborators and I found that they integrate multiple sensory and flight tactics to keep erratically flying moths within detection range. In pigeons, we discovered that individuals anticipating drone attacks adjust their positions toward the rear within the flock. I will also introduce an experimental framework that enables controlled interactions between real animals and virtual agents driven by reactive motion control, allowing quantitative tests of navigation efficiency. Through this seminar, I aim to highlight how studies of predator-prey navigation can bridge biology and engineering, providing insights into adaptive decision-making in dynamic environments.

会場: セミナー室 (359号室) / via Zoom

イベント公式言語: 英語

Chiral anomaly in Hamiltonian lattice gauge theory

2025年11月18日(火) 10:00 - 12:00

山本 新 (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 量子数理科学チーム 上級研究員)

The 4th quantum computing gathering organized by Quantum Computing Study Group

会場: セミナー室 (359号室) (メイン会場) / via Zoom

イベント公式言語: 英語

Contribution of star-forming galaxies to the cosmic gamma-ray background

2025年11月14日(金) 14:00 - 15:15

Junling Chen (東京大学 大学院数理科学研究科 博士課程)

Fermi Gamma-Ray Space Telescope has measured the diffuse extragalactic gamma-ray background (EGB) radiation in the energy range of 100 MeV to 820 GeV. Several candidate γ -ray sources have been proposed as the candidate components of the unresolved EGB, including active galactic nuclei (AGNs), millisecond pulsars, dark matter annihilation, and star-forming galaxies (SFGs), but their quantitative contribution has not yet been precisely determined. In this talk, I will introduce our latest physical model describing the gamma-ray emission mechanism from SFGs, and our estimate of the contribution of SFGs based on careful calibration with gamma-ray luminosities of nearby galaxies and physical quantities (star formation rate, stellar mass, and size) of galaxies observed by high-redshift galaxy surveys.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

The Uchuu simulations data set: large-scale structures and galaxies - Tomoaki Ishiyama

2025年11月13日(木) 14:00 - 15:30

石山 智明 (千葉大学 情報戦略機構 准教授)

I will introduce the Uchuu suite of large high-resolution cosmological N-body simulations. The largest simulation, named Uchuu, consists of 2.1 trillion dark matter particles in a box of side-length 2.0 Gpc/h, with particle mass of 3.27e8 Msun/h. The highest resolution simulation, Shin-Uchuu, consists of 262 billion particles in a box of side-length 140 Mpc/h, with particle mass of 8.97e5 Msun/h. Combining these simulations, we can follow the evolution of dark matter haloes and subhaloes spanning those hosting dwarf galaxies to massive galaxy clusters across an unprecedented volume from very high-z. We release N-body data (halo/subhalo catalogs and merger trees) and mock galaxy/AGN catalogs constructed using various models, which cover objects from z=0 to very high-z. These catalogs open a new window on understanding the large-scale structures and galaxy formation. In this presentation, I will also introduce results of cosmological simulations adopting a time-varying dark energy, conducted on the supercomputer Fugaku.

会場: セミナー室 (359号室) 3階 359号室とZoomのハイブリッド開催

イベント公式言語: 英語

DA Seminar: Machine learning for precipitation estimation and forecasting / Analysis of a Long-Lived Supercell: Life Cycle and Severe Weather Patterns in Northern Buenos Aires Province

2025年11月13日(木) 10:30 - 12:00

フアン・ルイス (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 予測科学研究チーム 客員研究員)
ルチアーノ・ヴィダル (理化学研究所 数理創造研究センター (iTHEMS) 数理展開部門 予測科学研究チーム 客員研究員)

Title: Machine learning for precipitation estimation and forecasting Speaker: Dr. Juan Ruiz (University of Buenos Aires – CONICET) Abstract: Estimating and forecasting precipitation is essential for a wide range of human activities as well as for disaster prevention. In this talk we will discuss the application of deep neural networks to the estimation of precipitation with high time and spatial resolution, combining remote sensors and numerical weather predictions. The proposed models show that these information sources can be effectively combined to improve the accuracy of real-time precipitation estimates. Additionally, we will present the application of deep neural networks as a postprocessing tool for short-range deterministic and ensemble-based numerical weather predictions and for the quantification of their uncertainty. The performance of the machine-learning models in the quantification of the uncertainty is close to that achieved by the dynamical ensembles and can be even better in the presence of a model. Title: Analysis of a Long-Lived Supercell: Life Cycle and Severe Weather Patterns in Northern Buenos Aires Province Speaker: Dr. Luciano Vidal (National Meteorological Service, Argentina) Abstract: This work presents a detailed analysis of a long-lived convective supercell that affected the northern Buenos Aires province, Argentina, on March 19, 2024. The primary objective is to characterize its life cycle and associated severe weather patterns using an integrated multi-sensor approach. This methodology combines data from satellite imagery with documentation of surface damage caused by large hail and intense winds. The storm exhibited a remarkable longevity, traveling approximately 400 km over 5.5 hours and impacting a total of 11 municipalities before its dissipation. Throughout its trajectory, the supercell generated significant damage due to large hail and severe wind gusts that, in some areas, exceeded 150 km/h. Furthermore, the storm ultimately affected the Sarandí-Santo Domingo basin (the pilot basin of the Argentine-Japanese SATREPS/PREVENIR project) by generating flash floods. The results of this analysis provide crucial information for the improvement of forecasting and early warning systems for severe weather events in the region.

会場: Hybrid Format (RIKEN R-CCS room 107 and Zoom)

イベント公式言語: 英語