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

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

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

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 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

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

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 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

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

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

Quantitative characterization of microbial diversity and environmental adaptation

2026年2月5日(木) 13:00 - 14:30

松本 美緒 (理化学研究所 開拓研究所 (PRI) 鈴木地球・惑星生命科学研究室 大学院生リサーチ・アソシエイト)
鈴木 志野 (理化学研究所 開拓研究所 (PRI) 鈴木地球・惑星生命科学研究室 主任研究員)

イベント公式言語: 英語

Scalable Simulation of Quantum Many-Body Dynamics with Or-Represented Quantum Algebra

2026年2月4日(水) 14:30 - 16:00

Lukas Broers (理化学研究所 計算科学研究センター (R-CCS) 量子系物質科学研究チーム 特別研究員)

High-performance numerical methods are essential for advancing quantum many-body physics, as well as for enabling the integration of supercomputers with emerging quantum computing platforms. We have developed a scalable and general-purpose numerical framework for quantum simulations based on or-represented quantum algebra (ORQA). This framework applies to arbitrary spin-systems and naturally integrates with quantum circuit simulation in the Heisenberg picture, particularly relevant to recent large-scale experiments on superconducting qubit processors [Kim et al., Nature 618, 500 (2023)]. As a benchmark, we simulate the kicked Ising model on a 127-qubit heavy-hexagon lattice, successfully tracking the time-evolution of local magnetization using up to one trillion Pauli strings. Our simulations exhibit strong scaling up to 2^17 parallel processes with near-linear communication overhead. Further, we show that our framework is naturally extended to a broader range of quantum systems, superseding the capabilities of recently established Pauli propagation methods. We present possible future directions on how to utilize our algorithm.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

From Wavefunction Sparsity to Quantum Filter-Assisted Subspace Diagonalization

2026年2月4日(水) 13:00 - 14:30

Han Xu (理化学研究所 計算科学研究センター (R-CCS) 量子系物質科学研究チーム 特別研究員)

Subspace diagonalization techniques based on quantum sampling, such as quantum selected configuration interaction (QSCI) and sample-based quantum diagonalization (SQD), are a class of quantum-centric algorithms for approximating ground-state energies of many-body systems. One of the foundational bottlenecks for SQD is due to the lack of compactness of the ground-state wavefunctions. In this talk, we will introduce a filter-assisted SQD protocol that enhances the wavefunction sparsity through a quantum-circuit transformation of the Hamiltonian. Using the Gini coefficient as a robust sparsity measure, we clarify how sparsity determines the resource requirements of SQD. To construct the quantum filter, we develop a tensor-network-based automatic circuit-encoding algorithm that encodes the target matrix product states with controllable fidelity. We benchmark the method on the quantum Ising model under the transverse and longitudinal fields, using both numerical simulations and experiments on IBM quantum hardware. Our results show that the filter-assisted protocol reduces energy-estimation errors by orders of magnitude and substantially lowers the overhead of measurement compared with standard SQD, which highlight the potential of filter-assisted protocol in quantum-centric computing for strongly correlated materials.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語