Analog variational quantum eigensolver for neutral atomic quantum simulators

2026年1月20日(火) 10:00 - 12:00

長尾 一馬 (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)

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

Evolution of sterile soldier castes in aphids

2026年1月21日(水) 13:00 - 14:00

植松 圭吾 (慶応義塾大学)

This seminar is jointly organized with the RIKEN Center for Sustainable Resource Science (CSRS). Social evolution in aphids is tightly linked to the formation of galls on their host plants. Galls provide efficient colony defense and nutritionally rich feeding sites such that colony members need not forage outside, leading to high intra-group relatedness. Typically, social aphids form a gall on their primary host plant, after which winged morphs disperse to secondary host plants and establish a free-living, open colony. Remarkably, sterile soldier castes have independently evolved twice in these open colonies, where individuals live on plant surfaces without modifying their structure. These aphids raise intriguing questions about the prerequisites for eusocial evolution and the mechanisms by which two distinct social systems are maintained within a single genome. In this talk, I will first provide an overview of the life cycle and the diversity of altruistic behaviors in gall-forming aphids, and then present our studies of the evolution of a sterile soldier caste in aphids inhabiting open colonies. From a developmental perspective, we tested the hypothesis that the sterile soldiers evolved through the co-option of pre-existing soldier phenotypes in a gall, based on similarity in morphology, transcriptome and behavior. From an ecological perspective, we investigated the kin structure and altruistic behavior of young nymphs in the open colonies of pre-eusocial species, and demonstrate that young aphids exhibit altruism by yielding feeding sites to older kin. Together, we propose that the open colonies of social aphids provide an ideal model system for studying the evolution of altruism.

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 (メイン会場) / via Zoom

イベント公式言語: 英語

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

DEEP-IN-iPI Joint Meeting

2026年1月26日(月) - 30日(金)

郭 星雨 (Lecturer, Institute of Quantum Matter, South China Normal University, China)
Gert Aarts (Professor, Department of Physics, Swansea University, UK)
施 舒哲 (Assistant Professor, Physics Department, Tsinghua University, Beijing, China)
Sung Hak Lim (Senior Researcher, Center for Theoretical Physics of the Universe (CTPU-PTC), Institute for Basic Science (IBS), Republic of Korea)
ジンヤン・リー (総合研究大学院大学 素粒子原子核コース 博士課程)

The series of DEEP-IN meetings (Jan 26–30, 2026) are joint with UTokyo Institute for Physics of Intelligence (iπ), which is a multi-day scientific program bringing together researchers to explore quantum simulations, machine learning physics, and applications in particle and nuclear physics. The tentative schedule is, UTokyo-iπ Session (Venue: #512, Faculty of Science Bldg.1, School of Science, UTokyo) Day 1: Jan 26 (Mon) 14:30–16:00 Onset of Bjorken flow in a quantum many-body simulation of the massive Schwinger model, Shuzhe Shi Day 2: Jan 27 (Tue) 14:30–16:00 Physics of Diffusion Models, Gert Aarts 16:00–17:30 Discovering Symmetry from Energy-Based Diffusion Models, Jinyang Li RIKEN-iTHEMS Session (Venue: Seminar Room #359, Main Research Building) Day 3: Jan 28 (Wed) 14:30–16:00 Understanding Galactic Dark Matter with Generative Models, Sung Hak Lim 16:00–18:00 Free Discussion ML Physics-1 Day 4: Jan 29 (Thu) 10:00–11:30 Quantum Simulations of HEP and Beyond, Xingyu Guo 14:30–16:00 Physics of Machine Learning, Gert Aarts Day 5: Jan 30 (Fri) 11:00–14:00: Free Discussion ML Physics-2

会場: via Zoom / セミナー室 (359号室) / 東京大学 本郷キャンパス 理学部１号館

イベント公式言語: 英語

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

Gauge fixing for open systems: A pathway to open gravity EFTs

2026年1月30日(金) 14:00 - 16:00

Maria Mylova (カブリ数物連携宇宙研究機構 (Kavli IPMU) 特任研究員)

Understanding how to gauge-fix open quantum field theories is essential for building consistent open frameworks for cosmology and gravity, where gauge symmetry must coexist with dissipation and noise and decoherence. I will present our recent work developing explicit top-down constructions of open effective field theories (EFTs) for gauge degrees of freedom, with particular emphasis on the role of gauge fixing. We implement BRST quantisation on the Schwinger-Keldysh contour and show that the in-in boundary conditions reduce the doubled global BRST symmetry to a single diagonal copy. This diagonal BRST symmetry is nevertheless sufficient to guarantee that the influence functional remains gauge invariant under two independent gauge transformations, retarded and advanced, independently of the choice of initial state, the presence of symmetry-breaking phases, and whether the gauge theory is Abelian or non-Abelian. We further clarify how this is compatible with the decoupling limit, in which the global advanced symmetry is generically broken by the state. I will conclude by outlining bottom-up implications, and how these principles provide a systematic route to causal, gauge-invariant open EFTs suitable for cosmological and gravitational applications.

会場: 研究本館 4階 445-447号室 (Hybrid)

イベント公式言語: 英語

Mathematical Application Research Team Meeting #12

2026年2月6日(金) 14:00 - 15:30

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)

Mathematical Application Research Team invites Riccardo Muolo fom Division of Fundamental Mathematical Science to this meeting. You are welcome to join the meeting. Title: Dynamics beyond nodes: a topological framework for oscillatory dynamics on higher-order networks Abstract: In recent years, increasing attention has been given to dynamical processes taking place on higher-order networks, where interactions are not limited to links, but may involve also higher-dimensional simplices [1]. While classical network models assume that state variables live on nodes and interact through links, many real systems — including brain, climate, and transportation systems — cannot be fully described within this node-centric perspective [2]. In this seminar, I will introduce the framework of higher-order networks and the concept of topological signals, namely, dynamical variables defined on simplices of higher dimensions. I will briefly present the basic tools required for this setting, including elementary notions of discrete calculus, discrete topology and geometric algebra, which serve as the mathematical foundation for modeling dynamical processes beyond the node-based paradigm. Next, I will discuss models of oscillatory dynamics extended to this framework. First, I will present the topological Kuramoto model [3], in which phases are not restricted to nodes but may also be associated with links, and where the coupling arises from the combinatorial structure of the simplicial complex. Then, I will introduce the discrete Hodge Laplacian and the Dirac-Bianconi operator [4], the former generalizing diffusive interactions to the higher-order setting, while the latter provides cross-talk between signals defined on simplices of different dimensions. Finally, I will introduce the notion of Dirac-Bianconi driven oscillators, where the dynamics of node- and link-signals coexist, interact and may give rise to collective oscillatory behaviors [5].

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

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

Lie Algebraic Saddles of the IKKT Matrix Model

2026年2月24日(火) 14:00 - 16:00

Henry Liao (Ph.D. Student, Department of Physics, National Taiwan University, Taiwan)

This semi-informal seminar will feature about one hour of prepared presentation, with ample time reserved for questions and discussion. Abstract: The IKKT matrix model as a promising non-perturbative formulation of type IIB superstring theory has been studied extensively over the past few decades both numerically and analytically. However, due to the nonlinear nature of its equations of motion, the saddle structure of the IKKT matrix model remains underexplored. In this talk, we consider the matrix degrees of freedom to be representations of finite dimensional Lie algebra, and discuss how to construct saddles accordingly. As a physical example, we apply dequantization map to discuss how curved spacetime can emerge from these saddles.

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

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

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

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