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604 件
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セミナー
Clumpy Outflows from Super-Eddington Accreting Black Holes
2026年4月10日(金) 14:00 - 15:15
Haojie Hu (筑波大学 JSPS海外特別研究員)
Recent advances in X-ray spectroscopic observation have enabled researchers to reveal distinct clumpy structures in the super-Eddington outflows from the supermassive black hole in PDS 456 (XRISM Collaboration 2025), initiating detailed investigation of fine-scale structures in accretion-driven outflows. In this talk, I will introduce our high-resolution, two-dimensional radiation-hydrodynamics simulations with time-varying and anisotropic initial and boundary conditions that reproduce clumpy outflows from super-Eddington accretion flows. The resulting clumpy outflows extend across a wide range of radial distances and polar angles, exhibiting typical properties such as a size of ~10 rg (where rg is the gravitational radius), a velocity of ~0.05–0.2 c (where c is the speed of light), and about five clumps along the line of sight. Although the velocities are slightly smaller, these characteristics reasonably resemble those obtained from the XRISM observation. The gas density of the clumps is on the order of 10^-13–10^-12 g cm^-3, and their optical depth for electron scattering is approximately 1–10. The clumpy winds accelerated by radiation force are considered to originate from the region within <300 rg.
会場: 研究本館 2階 220号室 (メイン会場) / via Zoom
イベント公式言語: 英語
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ワークショップ
KEK-iTHEMS Workshop “Concepts of Quantum and Spacetime”
2026年3月9日(月) - 12日(木)
The two fundamental questions—“What is quantum?” and “What is spacetime?”—are deeply intertwined. On one hand, the formulation and interpretation of quantum theory depend both implicitly and explicitly on our conceptions of time and space. On the other hand, we believe that fully taking into account the quantum character of nature will force us to revise our understanding of spacetime. These two conceptual problems lie at the heart of the unsolved challenge of how to quantize classical spacetime, and conversely, how (semi-) classical descriptions of spacetime emerge from quantum theory. Furthermore, if the entire matter-spacetime system is a kind of quantum many-body system, thermodynamics—which governs its statistical behaviors—should play a key role in elucidating these problems. This workshop will discuss the question “How can quantum theory and spacetime be understood in a consistent manner?” from a fundamental and broad perspective. To tackle this challenge, we gather researchers in foundations of quantum theory, quantum gravity, and related fields from around the world, providing a "space and time" to share various ideas with open minds and engage in lively discussions. By exploring new concepts and principles, we hope to uncover directions to guide quantum theory over the next 100 years. This workshop covers… Foundations of quantum theory Quantum gravity and emergence of spacetime Formulation of semi-classical gravity Experimental aspects of fundamental properties in nature and quantum gravity Foundations of quantum many-body systems and thermodynamics Other related topics are welcome. We welcome short talk presentations and poster presentations. This event is a workshop jointly organized by KEK Theory Center and RIKEN iTHEMS.
会場: Seminar Hall, Building 3, KEK
イベント公式言語: 英語
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ワークショップ
RIKEN iTHEMS-Kyoto University joint workshop on Asymptotics in Astrophysics and Cosmology
2026年3月2日(月) - 4日(水)
This joint workshop will bring together physicists and mathematicians who work with asymptotics and perturbation theory techniques. This includes theorists in cosmology, high energy physics, quantum gravity, solar physics, astrophysics. Workshop overview Over three days, there will be approximately 15 invited (1 hour slot) or contributed (20-30 min slot) talks about: Fundamental asymptotics and perturbation theory techniques used in theoretical physics. Various applications of asymptotics and perturbation theory techniques in (wave transport or oscillation related) astrophysics and cosmology eigenvalue problems. The workshop will also feature hands-on Mathematica and Python tutorials introducing: Practical use of WKB methods in applied mathematics for any “Schrodinger-like” wave equations, Resummation methods in high energy theory, Deriving normal modes in stars, and their application to tidal evolution in binary star or planet systems, Eigenvalue problems in core collapse supernova theory.
会場: 融合連携イノベーション推進棟（IIB） 8階
イベント公式言語: 英語
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セミナーWhat can we learn from kilonovae about nucleosynthesis and high-density matter?
2026年2月9日(月) 14:00 - 15:15
オリバー・ユスト (Postdoctoral Researcher, GSI Helmholtzzentrum für Schwerionenforschung, Germany)
The electromagnetic transients accompanying neutron-star mergers (NSMs), called kilonovae, are powered by the radioactive decay of freshly synthesized heavy elements. As such they should contain rich information about the ejected matter and the properties of the extremely dense meta-stable neutron-star remnant formed right after the collision. However, extracting such information from observed kilonova light curves and spectra remains a challenging endeavor, which requires sophisticated models of various hydrodynamic processes and neutrino transport effects, detailed knowledge of nuclear and atomic physics, as well as complex radiative transfer calculations. In this talk I will report recent efforts from our "HeavyMetal" collaboration aimed at deciphering kilonovae.
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
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ワークショップ
iTHEMS Cosmology Forum n°5 - Effective Field Theory approaches across the Universe
2026年1月29日(木) 10:00 - 17:00
青木 勝輝 (京都大学 基礎物理学研究所 基研特任助教)
野海 俊文 (東京大学 大学院総合文化研究科 准教授)
Lucas Pinol (CNRS Researcher, LPENS, CNRS/École Normale Supérieure, France)This fifth workshop will bring together researchers exploring the effective field theory (EFT) framework in diverse cosmological contexts. Topics will include EFT formulations of interacting dark matter and dark energy, open EFTs for gravity, and multi-field inflationary dynamics. By highlighting recent progress and open questions, the workshop seeks to bridge insights from the early and late universe through the unifying language of EFT. In addition to the invited talks, the workshop will feature a panel discussion designed to promote interaction between the speakers and participants. One of the key goals of this event is to foster collaboration among researchers working in neighboring fields, and to encourage participation from young and early-career researchers who are interested in, but may not yet have worked on, these themes. The workshop welcomes a broad audience with an interest in theoretical cosmology, gravitation, and quantum field theory. The workshops are organised by the Cosmology Study Group at RIKEN iTHEMS.
会場: 研究本館 4階 435-437号室
イベント公式言語: 英語
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スクール
New computational methods in quantum field theory 2026
2026年1月26日(月) - 28日(水)
Recent developments in quantum computers and related theoretical/technical advancements have brought attention to "new computational methods in quantum field theory" in the fields of high energy/nuclear physics. Main targets of this school are graduate students and postdocs. This school provides opportunities to discuss recent research trends and their applications through lectures by experts and presentations by participants. Lecturers: Junichi Haruna (University of Osaka) "Introduction to Quantum Error Correction (tentative)" Yoshimasa Hidaka (Yukawa Institute for Theoretical Physics/RIKEN iTHEMS) “Introduction to Hamiltonian Lattice Gauge Theory (tentative)” Tokiro Numasawa (University of Tokyo) "Open Majorana system (tentative)"
会場: 研究本館 4階 435-437号室
イベント公式言語: 英語
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コロキウムMeasuring evolutionary forces of cultural change
2026年1月13日(火) 14:00 - 15:30
ジョシュア・プロトキン (Walter H. and Leonore C. Annenberg Professor of the Natural Sciences, University of Pennsylvania, USA)
I will describe how to measure the forces that drive cultural change, using inference tools from evolutionary theory. We study time series data from large corpora of parsed English texts to identify what drives language change over the course of centuries. We also measure frequency-dependent effects in time series of baby names and purebred dog preferences. The form of frequency dependence we infer helps to explain the diversity distribution of names, and it replicates across the United States, France, Norway and the Netherlands. We find different growth laws for male versus female names, attributable to different rates of innovation, whereas names from the bible enjoy a genuine advantage at all frequencies. Frequency dependence emerges from a host of underlying social and cultural mechanisms, including a preference for novelty that recapitulates fashion trends in dog owners. Studying culture through the lens of evolutionary theory provides a quantitative account of social pressures to conform or to be different; and it provides inference tools that may be used in biology as genetic and phenotypic time series are increasingly available.
会場: 大河内記念ホール (メイン会場) / via Zoom
イベント公式言語: 英語
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セミナー
Higher Gauge Structures and Invariant Action Principles
2026年1月6日(火) 15:15 - 16:15
Sebastián Salgado (External Researcher, Instituto de Alta Investigacion, Universidad de Tarapaca, Chile)
I present the systematic construction of gauge theories based on free differential and L-infinity algebras. This provides a consistent algebraic framework for constructing gauge-invariant theories whose field content is extended by higher-degree differential forms as gauge potentials. I derive explicit expressions for the corresponding extended Chern-Simons actions and the generalized anomaly terms that emerge from them. Possible applications to gravity and supergravity will also be discussed.
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
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セミナー
Invitation to Random Tensor Models: from random geometry, enumeration of tensor invariants, to characteristic polynomials
2026年1月6日(火) 13:30 - 14:30
鳥海 玲子 (沖縄科学技術大学院大学 (OIST) 准教授)
I will introduce random tensor models by first reviewing their motivation coming from random geometric approach to quantum gravity. Then, I will selectively present some of the interesting research results, by highlighting recent results on enumeration of graphs representing tensor invariants, and reporting our recent work on a new notion of characteristic polynomials for tensors via Grassmann integrals and distributions of roots of random tensors. The latter two are based on arXiv:2404.16404[hep-th] and arXiv:2510.04068[math-ph]
会場: 研究本館 3階 359号室 (メイン会場) / via Zoom
イベント公式言語: 英語
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セミナー 明日開催
Cosmological correlators beyond the de-Sitter invariance
2025年12月24日(水) 15:00 - 17:00
Zhu Yuhang (Postdoctoral Researcher, Particle Theory and Cosmology Group, Center for Theoretical Physics of the Universe (CTPU), Institute for Basic Science (IBS), Republic of Korea)
Cosmological correlators serve as powerful probes of the physics that governed the Universe in its earliest moments. Yet analytic calculations of correlators involving massive spinning fields are highly challenging. Recent progress in the cosmological bootstrap program has greatly deepened our understanding of these correlators. In this talk, we will show how to extend the bootstrap program beyond exact de Sitter invariance by studying two types of symmetry breaking: explicit scale-invariance breaking and boost breaking. We will present the boundary differential equations that characterise correlators in these settings and highlight the rich phenomenology that emerges. Finally, we will also show recent developments in approximation methods, based on the combination of exact WKB and saddle-point method, which provide a precise, efficient, and physically transparent way to capture and classify the non-analytic features of correlators.
会場: via Zoom / セミナー室 (359号室)
イベント公式言語: 英語
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セミナー
Origin and evolutionary history of an urban underground mosquito
2025年12月18日(木) 13:00 - 14:00
羽場 優紀 (Postdoc, Zuckerman Institute, Columbia University, USA)
Urbanization is rapidly reshaping landscapes around the world, which poses questions about whether and how quickly animals and plants can adapt. Culex pipiens form molestus, more commonly known as the "London Underground mosquito," has been held up as a benchmark for the potential speed and complexity of urban adaptation. This intraspecific lineage within Cx. pipiens, a major West Nile virus vector, is purported to have evolved human biting and a suite of other human-adaptive behaviors in the subways and cellars of northern Europe within the past 200 years. Form molestus features prominently in textbooks as well as scholarly reviews of urban adaptation. Yet, the hypothesis of in situ urban evolution has never been rigorously tested. I will talk our recent efforts to understand the contentious origin and evolutionary history of the urban, human-biting mosquito. Our synthesis and meta-analysis of rich yet confusing literature show that its London Underground origin is unlikely (Haba and McBride 2022 Current Biology). Whole genome resequencing and population genomics of 800+ mosquitoes across ~50 countries again debunk the in situ evolution hypothesis and instead support that molestus first adapted to human environments >1000 years ago in the Mediterranean or Middle East, most likely in ancient Egypt or another early agricultural society (Haba et al. 2025 Science). I will outline implications of our results in urban evolutionary biology as well as in public health. Speaker Bio Yuki Haba, Ph.D., is an evolutionary biologist passionate about understanding how and why diverse behaviors evolve in nature. He is currently a Leon Levy Scholar in Neuroscience at Columbia University's Zuckerman Mind Brain Behavior Institute. He aims to take multi-desciplinary approaches, combining genomics, neuroscience, and field-based behavioral ecology to comprehensively understand the evolution of behavior. Yuki completed his PhD at Princeton, MA at Columbia, and undergraduate degree at the University of Tokyo. Personal webpage: https://yukihaba.github.io/
会場: セミナー室 (359号室)
イベント公式言語: 英語
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セミナー
Is the Fornax galaxy cluster hiding its radio sources?
2025年12月15日(月) 14:00 - 15:15
Alvina Yee Lian On (PD, Physics Division, National Center for Theoretical Sciences, Taiwan)
Recently, the ASKAP POSSUM and MeerKAT surveys revealed an apparent lack of radio source counts in the Fornax galaxy cluster field. The sources in this patch of sky also appeared to be less polarised. These observations are peculiar and could be important signatures of depolarisation on megaparsec scales. In this talk, I will present some of our recent results, where we quantified the effects on polarisation of radio point sources behind a merging galaxy cluster simulation. The merger gives rise to a large-scale intracluster shock, which compresses the gas and aligns the magnetic field along the shock front. The in-falling subcluster also triggers gas sloshing near the cluster center, resulting in the formation of cold fronts. Our ray-tracing calculations revealed that, generally, bright sources do not experience any significant changes in polarisation, whereas faint sources either get severely depolarised or enhanced as their radiation propagates through the intracluster medium. I will highlight the physical conditions under which polarisation may change significantly along the line-of-sight and discuss how these may impact our interpretations of radio observations, particularly with the SKA.
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
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セミナー
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
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その他
京都大学MACSプログラムスタディグループ 理研訪問・研究交流会 —理研研究者と語る最前線—
2025年12月12日(金) 12:30 - 15:10
12:00 – 13:30 コーヒーミーティング参加 13:30 – 14:10 入谷 亮介 (理研 iTHEMS 上級研究員) — 研究キーワード:数理生物学, 進化生態学 14:10 – 14:30 休憩 14:30 – 15:10 森川 億人 (理研 iTHEMS 基礎科学特別研究員) — 研究キーワード: 格子場の理論, 共形場理論, 場の量子論, 素粒子論
会場: 研究本館 3階 345-347室
イベント公式言語: 日本語
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セミナー
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
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セミナー
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
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セミナー
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
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セミナー
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
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セミナー
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