JST-Sakura Science Exchange Program: AI for Atmospheric Science

2026年2月4日(水) - 10日(火)

This JST-Sakura Science Exchange Program leverages the complementary strengths and research foundations of Fudan University and RIKEN in atmospheric science, focusing on the important scientific challenge of applying artificial intelligence to cloud remote sensing and data assimilation. The exchange program also includes one-day workshop in R-CCS with Data Assimilation Research Team.

会場: 融合連携イノベーション推進棟（IIB） (メイン会場) / via Zoom / RIKEN Center for Computational Science, 1F Seminar room

イベント公式言語: 英語

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

Finite-size effects on the QCD critical point

2026年2月9日(月) 15:30 - 17:30

Gyozo Kovacs (Research Fellow, Institute of Theoretical Physics, University of Wroclaw, Poland)

[Joint seminar hosted by QMS Team (iTHEMS) and FTR Team (R-CCS)] While effective approaches are important tools in the search for the QCD critical point, the physical systems they describe differ in several aspects from those in heavy-ion collisions and from unextrapolated lattice QCD. A primary discrepancy is the system size, which is infinite only in effective model calculations. Various implementations exist to account for the resulting finite-size effects. Beyond the frequently used methods, we present a comprehensive mean-field approach that allows for both infinite- and finite-size calculations, even within a complex parameter space. We discuss the general impact of finite-size effects on key observables, such as conserved charge fluctuations, and on the analytic structure of the thermodynamic potential. 15:30-16:30 Lecture 16:30-17:30 Discussion with coffee

会場: 研究本館 (メイン会場) / via Zoom

イベント公式言語: 英語

Quantum Electrodynamics of Strong Laser-Matter Interaction: The Ongoing Journey and Beyond

2026年2月10日(火) 10:00 - 12:00

Ciappina Marcelo (Professor, Guangdong Technion, China)

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

Monitoring the complexity and dynamics of mitochondrial translation

2026年2月12日(木) 16:00 - 17:00

脇川 大誠 (理化学研究所 開拓研究所 (PRI) 岩崎RNAシステム生化学研究室 リサーチアソシエイト)

Since mitochondrial translation leads to the synthesis of the essential oxidative phosphorylation (OXPHOS) subunits, exhaustive and quantitative delineation of mitoribosome traversal is needed. Here, we developed a variety of high-resolution mitochondrial ribosome profiling derivatives and revealed the intricate regulation of mammalian mitochondrial translation. Harnessing a translation inhibitor, retapamulin, our approach assessed the stoichiometry and kinetics of mitochondrial translation flux, such as the number of mitoribosomes on a transcript, the elongation rate, and the initiation rate. We also surveyed the impacts of modifications at the anticodon stem loop in mitochondrial tRNAs (mt-tRNAs), including all possible modifications at the 34th position, in cells deleting the corresponding enzymes and derived from patients, as well as in mouse tissues. Moreover, a retapamulin-assisted derivative and mito-disome profiling revealed mitochondrial translation initiation factor (mtIF) 3-mediated translation initiation from internal open reading frames (ORFs) and programmed mitoribosome collision sites across the mitochondrial transcriptome. Our work provides a useful platform for investigating protein synthesis within the energy powerhouse of the cell.

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 geometric tensor determines the i.i.d. conversion rate in the resource theory of asymmetry for any compact Lie group

2026年2月13日(金) 10:00 - 11:30

山口 幸司 (九州大学 大学院システム情報科学研究院 特任助教)

If you are not affiliated with RIKEN, please register using the registration form. Registration deadline: 12nd Feb. (Thu), 2026 Quantifying physical concepts in terms of the ultimate performance of a given task has been central to theoretical progress, as illustrated by thermodynamic entropy and entanglement entropy, which respectively quantify irreversibility and quantum correlations. Symmetry breaking is equally universal, yet lacks such an operational quantification. While an operational characterization of symmetry breaking through asymptotic state-conversion efficiency is a central goal of the resource theory of asymmetry (RTA), such a characterization has so far been completed only for the group among continuous symmetries. Here, we identify the complete measure of symmetry breaking for a general continuous symmetry described by any compact Lie group. Specifically, we show that the asymptotic conversion rate between many copies of pure states in RTA is determined by the quantum geometric tensor, thereby establishing it as the complete measure of symmetry breaking. As an immediate consequence of our conversion rate formula, we also resolve the Marvian-Spekkens conjecture on conditions for reversible conversion in RTA, which has remained unproven for over a decade. By applying our analysis to a standard setup in quantum thermodynamics, we show that asymptotic state conversion under thermal operations generally requires macroscopic coherence in the thermodynamic limit.

会場: セミナー室 (359号室) 3階 359号室

イベント公式言語: 英語

Persistent homology and its applications

2026年2月17日(火) 11:00 - 12:00

池 祐一 (東京大学 大学院数理科学研究科 准教授)

Persistent homology is one of the main tools in topological data analysis (TDA), which encodes the topological features of given data into persistence diagrams. It has been successfully applied to various fields such as material science and computer graphics. In this talk, I will provide an overview of persistent homology and its applications. Furthermore, I will also discuss its integration with machine learning, specifically how persistent-homology-based loss functions can be used to regularize the topological structure of parameters.

会場: セミナー室 (359号室)

イベント公式言語: 英語

The Rectangular Peg Problem and microlocal sheaf theory

2026年2月17日(火) 14:00 - 15:00

池 祐一 (東京大学 大学院数理科学研究科 准教授)

The Square Peg Problem asks whether every Jordan curve in the plane contains four distinct points that form the vertices of a square. This problem was proposed by Toeplitz in 1911 and remains unsolved in full generality. It can be generalized to the Rectangular Peg Problem, which concerns the existence of inscribed rectangles with a prescribed aspect ratio. Recently, Greene and Lobb successfully applied techniques in symplectic geometry to the problem and obtained new results. In this talk, I will explain how microlocal sheaf theory allows us to further extend their approach and affirmatively solve the Rectangular Peg Problem for a large class of Jordan curves, including all curves of finite length. This is joint work with Tomohiro Asano.

会場: セミナー室 (359号室)

イベント公式言語: 英語

Taming the Butterfly: A New "Duality Principle" Turns Chaos into Control

2026年2月18日(水) 13:00 - 14:00

三好 建正 (理化学研究所 計算科学研究センター (R-CCS) データ同化研究チーム チームプリンシパル)

Data Assimilation (DA) is the backbone of modern weather forecasting. It integrates observational data into computer simulations to synchronize the model with nature. The Duality Principle posits that chaos control is mathematically the "twin" (dual) of DA. Data Assimilation: Uses observations to synchronize the Model to Nature. Chaos Control: Uses interventions to synchronize Nature to a desired Model ("target trajectory"). "The butterfly effect has long been a symbol of unpredictability," says Dr. Miyoshi. "But I asked a simple question: If a butterfly's wings can change the future, does that not imply that with the right, tiny push, we could choose a better future?" Instead of suppressing the chaotic system with massive force, this method acts like mathematical judo—leveraging the system's inherent instability. By applying minute, calculated "interventions" (analogous to the butterfly's flap), the system can be guided toward a "target trajectory"—for instance, shifting real-world conditions just enough to align with a model-simulated scenario where a typhoon causes no damage. Once synchronized, control becomes much easier to maintain. This study establishes the theoretical foundation for "Control Simulation Experiments" (CSE), a framework previously proposed by Miyoshi’s team. It provides a roadmap for future disaster prevention research, moving beyond passive prediction to active mitigation. Beyond meteorology, this general framework is expected to serve as a universal tool for studying interventions in various chaotic systems, from ecosystems to economics. Following the seminar, we will hold an informal discussion (brainstorming) on data assimilation with quantum computing in the same room from 2-4 pm.

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

Brainstorming session on data assimilation with quantum computing

2026年2月18日(水) 14:00 - 16:00

三好 建正 (理化学研究所 計算科学研究センター (R-CCS) データ同化研究チーム チームプリンシパル)

We will discuss the potential of quantum computing for applications in data assimilation.

会場: セミナー室 (359号室) 3階 359号室

イベント公式言語: 英語

第31回 MACSコロキウム・2025年度MACS成果報告会

2026年2月18日(水) 14:45 - 18:00

衞藤 雄二郎 (京都大学 大学院理学研究科 附属サイエンス連携探索センター (SACRA) 准教授)

14:45-15:00 ティータイムディスカッション [15:00-16:00 第31回MACSコロキウム 講演] 衞藤 雄二郎（京都大学大学院理学研究科 附属サイエンス連携探索センター 准教授）「明るい量子光源を使った量子計測」 [16:10-18:30 2025年度MACS成果報告会] 16:10-17:10 各スタディグルーブ フラッシュトーク 17:10-18:00 参加学生によるポスター発表

会場: 京都大学 理学研究科セミナーハウス（建物配置図（北部構内）【10】の建物）

イベント公式言語: 日本語

The sample complexity of species tree estimation: How many genes does it take to infer a species tree?

2026年2月19日(木) 13:00 - 14:00

Max Hill (Assistant Professor, University of Hawaiʻi, USA)

In this talk, I will discuss the problem of inferring an evolutionary tree from DNA sequence data. The main focus will be on the sample complexity of this problem---i.e., the question of how much data is required to achieve high probability of correct inference. After introducing a standard stochastic model of gene and DNA evolution, I will highlight some surprising features of DNA sequence data that complicate inference. Finally, I will present an impossibility result which takes the form of an information-theoretic lower bound on the minimum amount of data needed for accurate inference when genes exhibit variation in mutation rates. No prior knowledge of phylogenetics or information theory is assumed. Based on joint work with Sebastien Roch.

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

Binary neutron Star Merger as a Probe of Hadron-Quark Transition

2026年2月19日(木) 14:00 - 15:00

黄 永嘉 (Research Associate, Purple Mountain Observatory, Chinese Academy of Sciences, China)

This seminar is a joint seminar between GWX-EOS and the iTHEMS-ABBL Joint Astro SG. The recent rise of multi-messenger astronomy—including radius measurements from NICER, tidal deformability constraints from gravitational-wave events GW170817, and first-principles calculations from chiral effective field theory (χEFT) and perturbative QCD—has significantly tightened constraints on the neutron star equation of state. These advances consistently point to a non-monotonic sound speed in dense matter, suggesting that the cores of massive neutron stars may host exotic phases such as quark matter. However, the masquerade effect in static neutron stars makes it difficult to directly probe the nature of the transition (e.g., a smooth crossover or a sharp phase transition) near the core through observation alone.

会場: 理化学研究所 和光キャンパス (メイン会場) / via Zoom

イベント公式言語: 英語

Spectral Codes : A Geometric Formalism for QEC

2026年2月19日(木) 15:00 - 16:30

菅野 聡 (ソフトバンク株式会社 先端技術研究所 研究員)

In this talk, I will introduce a novel geometric framework for quantum error correction based on spectral triples in noncommutative geometry. In this formulation, quantum error-correcting codes are described as spectral projections onto the low-energy eigenspaces of Dirac-type operators, where the separation between logical information and local errors is captured geometrically. This approach provides a unified spectral and geometric understanding of key properties such as code distance and error thresholds. Moreover, it accommodates various existing codes, including classical linear codes, stabilizer codes, GKP codes, and topological codes. This geometric perspective also suggests intriguing connections to deformation quantization and holographic quantum error correction, offering promising directions for future research.

会場: セミナー室 (359号室) 3階 359号室

イベント公式言語: 英語

Basic Conceptual and Mathematical Problems of QFT

2026年2月20日(金) 14:00 - 15:30

クリスティ・コウジ・ケリー

In this talk we discuss some of the most basic conceptual and mathematical difficulties that arise in the standard physics analysis of QFT. In particular we shall discuss the origin of UV divergences in QFT—pointing out that there is both a kinematic and a dynamic aspect to this problem, and that the standard physics explanation (’new physics’) only considers the latter—and suggest that despite the notoriety of the problem, UV divergences are essentially under control. Secondly we discuss Haag’s theorem—which ensures the nonexistence of the interaction picture and the triviality of the perturbative S-Matrix—and indicate how this is the most elementary manifestation of a series of infrared problems in QFT. Finally we will outline why the rigorous construction of path-integral measures is difficult. If we have time, we may discuss some difficulties associated with gauge theories such as the infraparticle problem of QED and the mass-gap problem of Yang-Mills theory.

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

Testing the quantum nature of gravity with optomechanical systems

2026年2月26日(木) 10:00 - 12:00

道村 唯太 (東京大学 大学院理学系研究科 物理学専攻 助教)

Quantum gravity remains one of the major challenges in modern physics. Even at the most fundamental level, there is no experimental confirmation of whether a mass placed in a spatial superposition generates a corresponding superposition of gravitational fields. In recent years, experiments aiming to create gravity-induced quantum entanglement have attracted significant attention as a way to probe the quantum nature of non-relativistic gravity. In particular, optomechanical systems, which exploit the interaction between light and mechanical oscillators, provide a promising platform for such studies. We are pursuing experiments at the milligram scale, which lies between the smallest mass scale at which classical gravity has been tested and the largest mass scale at which quantum states of mechanical oscillators have been realized [1]. In this seminar, I will discuss experimental approaches to testing the quantum nature of gravity using suspended and levitated mirrors. I will also discuss our recent proposal to use inverted oscillators to enhance gravity-induced entanglement exponentially [2].

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 career talk: From Quarks to Cinematic Sparks

2026年2月27日(金) 15:00 - 16:30

Agnes Mocsy (Professor, Department of Mathematics and Science, Pratt Institute, USA)

While my career began in a linear way, it gradually opened into a non-traditional path through unexpected mergings, where theoretical nuclear physics, filmmaking, and creative public and academic engagement intertwined. I will share how scientific inquiry, artistic practice, and storytelling began shaping one another, opening new ways to explore complexity, emotion, and connection. Drawing on work from my physics research to cinema projects like Rare Connections, I will reflect on how curiosity and creative thinking move freely across science and art, deepening each and expanding how we understand the human experience. My aim is to offer a perspective on the possibilities that emerge when we allow our multitudes to meet and transform one another.

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

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

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

非可換ゲージ理論の量子シミュレーション

2026年3月17日(火) 18:00 - 19:00

花田 政範 (Reader, School of Mathematical Sciences, Queen Mary University of London, UK)

Kogut-Susskingハミルトニアンを用いればゲージ理論の量子シミュレーションができ、高エネルギー物理学の様々な問題を解けるはずであると言われて久しいのですが、実際にどのような研究がなされたのかを調べてみると、非可換ゲージ理論に関する論文が極端に少ないことに気が付きます。これは、Kogut-Susskingハミルトニアンは非可換ゲージ理論の場合にはとても複雑で、量子回路を構成する（ = プログラムをコンパイルする）以前に、そもそもハミルトニアンをqubitの言葉に書き直すための一般論すら存在しないからです。具体的には、無限次元のヒルベルト空間を正則化して有限自由度で近似する際に、SU(N)のような非自明な群多様体をどう扱えば良いのかが分かっていません。 この問題は、Kogut-Susskingハミルトニアンではなくてもっと筋の良いハミルトニアンを用いることで容易に回避できます。具体的には、Kaplan, Katz, Unsalによって構成されたorbifold lattice Hamiltonianを用いるのが便利です。Orbifold lattice Hamiltonianはゲージ場とスカラー場が相互作用する系を記述しますが、スカラー場は連続極限には寄与しません。（大きな質量を手で与えてUVの物理にすら寄与しなくすることも可能です。）しかし、ゲージ場とスカラー場をまとめて複素行列として記述するので、リンク変数がSU(N)ではなく\mathbb{C}^{N^2} = \mathbb{R}^{2N^2}に値をとります。たったこれだけの違いで、無限次元のヒルベルト空間の正則化が劇的に簡単になり、任意のSU(N)について効率的な量子回路を解析的に書き下すことが可能になります。 本講義では、量子シミュレーションの基礎から出発し、QCDを含む一般的な非可換ゲージ理論の時間発展を記述する量子回路を構成してシミュレーションコストを見積もるところまで解説したいと思います。 (3/17, 24, 31 の3回シリーズ)

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: 日本語

Perspectives and applications of Koopman Operator Theory

2026年3月19日(木) 9:00 - 18:00

薄 良彦 (京都大学 大学院工学研究科 教授)
中尾 裕也 (東京科学大学 工学院 システム制御系 教授)
Alexandre Mauroy (Associate Professor, Mathematics, University of Namur, Belgium)
加藤 譲 (公立はこだて未来大学 システム情報科学部 複雑系知能学科 准教授)

会場: 研究本館 5階 535-537号室

イベント公式言語: 英語

非可換ゲージ理論の量子シミュレーション

2026年3月24日(火) 18:00 - 19:00

花田 政範 (Reader, School of Mathematical Sciences, Queen Mary University of London, UK)

Kogut-Susskingハミルトニアンを用いればゲージ理論の量子シミュレーションができ、高エネルギー物理学の様々な問題を解けるはずであると言われて久しいのですが、実際にどのような研究がなされたのかを調べてみると、非可換ゲージ理論に関する論文が極端に少ないことに気が付きます。これは、Kogut-Susskingハミルトニアンは非可換ゲージ理論の場合にはとても複雑で、量子回路を構成する（ = プログラムをコンパイルする）以前に、そもそもハミルトニアンをqubitの言葉に書き直すための一般論すら存在しないからです。具体的には、無限次元のヒルベルト空間を正則化して有限自由度で近似する際に、SU(N)のような非自明な群多様体をどう扱えば良いのかが分かっていません。 この問題は、Kogut-Susskingハミルトニアンではなくてもっと筋の良いハミルトニアンを用いることで容易に回避できます。具体的には、Kaplan, Katz, Unsalによって構成されたorbifold lattice Hamiltonianを用いるのが便利です。Orbifold lattice Hamiltonianはゲージ場とスカラー場が相互作用する系を記述しますが、スカラー場は連続極限には寄与しません。（大きな質量を手で与えてUVの物理にすら寄与しなくすることも可能です。）しかし、ゲージ場とスカラー場をまとめて複素行列として記述するので、リンク変数がSU(N)ではなく\mathbb{C}^{N^2} = \mathbb{R}^{2N^2}に値をとります。たったこれだけの違いで、無限次元のヒルベルト空間の正則化が劇的に簡単になり、任意のSU(N)について効率的な量子回路を解析的に書き下すことが可能になります。 本講義では、量子シミュレーションの基礎から出発し、QCDを含む一般的な非可換ゲージ理論の時間発展を記述する量子回路を構成してシミュレーションコストを見積もるところまで解説したいと思います。 (3/17, 24, 31 の3回シリーズ)

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: 日本語

QFT as a set of ODEs

2026年3月27日(金) 13:30 - 15:30

Qiao Jiaxin (東京大学 カブリ数物連携宇宙研究機構 (Kavli IPMU) 特任研究員)

Correlation functions of local operators in Quantum Field Theory (QFT) on hyperbolic space can be fully characterized by the set of QFT data. These are the scaling dimensions of boundary operators, the boundary Operator Product Expansion (OPE) coefficients and the Boundary Operator Expansion (BOE) coefficients that characterize how each bulk operator can be expanded in terms of boundary operators. For simplicity, we focus on two dimensional QFTs and derive a universal set of first order Ordinary Differential Equations (ODEs) that encode the variation of the QFT data under an infinitesimal change of a bulk relevant coupling. In principle, our ODEs can be used to follow a renormalization group flow starting from a solvable QFT into a strongly coupled phase and to the flat space limit.

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

非可換ゲージ理論の量子シミュレーション

2026年3月31日(火) 18:00 - 19:00

花田 政範 (Reader, School of Mathematical Sciences, Queen Mary University of London, UK)

Kogut-Susskingハミルトニアンを用いればゲージ理論の量子シミュレーションができ、高エネルギー物理学の様々な問題を解けるはずであると言われて久しいのですが、実際にどのような研究がなされたのかを調べてみると、非可換ゲージ理論に関する論文が極端に少ないことに気が付きます。これは、Kogut-Susskingハミルトニアンは非可換ゲージ理論の場合にはとても複雑で、量子回路を構成する（ = プログラムをコンパイルする）以前に、そもそもハミルトニアンをqubitの言葉に書き直すための一般論すら存在しないからです。具体的には、無限次元のヒルベルト空間を正則化して有限自由度で近似する際に、SU(N)のような非自明な群多様体をどう扱えば良いのかが分かっていません。 この問題は、Kogut-Susskingハミルトニアンではなくてもっと筋の良いハミルトニアンを用いることで容易に回避できます。具体的には、Kaplan, Katz, Unsalによって構成されたorbifold lattice Hamiltonianを用いるのが便利です。Orbifold lattice Hamiltonianはゲージ場とスカラー場が相互作用する系を記述しますが、スカラー場は連続極限には寄与しません。（大きな質量を手で与えてUVの物理にすら寄与しなくすることも可能です。）しかし、ゲージ場とスカラー場をまとめて複素行列として記述するので、リンク変数がSU(N)ではなく\mathbb{C}^{N^2} = \mathbb{R}^{2N^2}に値をとります。たったこれだけの違いで、無限次元のヒルベルト空間の正則化が劇的に簡単になり、任意のSU(N)について効率的な量子回路を解析的に書き下すことが可能になります。 本講義では、量子シミュレーションの基礎から出発し、QCDを含む一般的な非可換ゲージ理論の時間発展を記述する量子回路を構成してシミュレーションコストを見積もるところまで解説したいと思います。 (3/17, 24, 31 の3回シリーズ)

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: 日本語

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