セミナー
928 イベント
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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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セミナー
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
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セミナー
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
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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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セミナー
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
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セミナー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 JFlow for Inferring Dark Matter, 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
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セミナー
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
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セミナーIntroduction to the gravitational wave background from the primordial universe
2026年1月16日(金) 16:00 - 17:15
難波 亮 (理化学研究所 数理創造研究センター (iTHEMS) 数理基礎部門 上級研究員)
Being genuine propagating degrees of freedom of the spacetime metric, gravitational waves (GWs) serve as an independent "eye" through which we can probe the evolution history of our universe. They are complementary to electromagnetic observables such as cosmic microwave background (CMB) and can act as direct messengers from the earliest stage of the universe, where conventional probes lose access. In particular, a stochastic background of GWs is widely regarded as a smoking gun of cosmic inflation. In this talk, I introduce the basic theoretical framework for GWs produced in the primordial universe and discuss how they arise from vacuum fluctuations of the metric. I also outline additional production mechanisms sourced by matter fields in the early universe and contrast their characteristic observational signatures with those of vacuum tensor modes. The emphasis of my talk will be on physical intuition and analytic derivations, with the aim of making the subject accessible to non-specialists in the astrophysics community.
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
A one-world interpretation of quantum mechanics
2026年1月16日(金) 14:00 - 16:00
Isaac Layton (東京大学 大学院理学系研究科 物理学専攻 ポスドク研究員)
The measurement problem arises in trying to explain how the objective classical world emerges from a quantum one. In this talk I’ll advocate for an alternative approach, in which the existence of a classical system is assumed a priori. By asking that the standard rules of probability theory apply to it when it interacts with a system linearly evolving in Hilbert space, I’ll show that with a few additional assumptions one can recover the unitary dynamics, collapse and Born rule postulates from quantum theory. This gives an interpretation of quantum mechanics in which classically definite outcomes are always assigned probabilities, rather than superpositions, giving one-world instead of many. The main technical tool used is a change of measure on the space of classical paths, the functional form of which characterises the quantum dynamics and Born rules of a class of quantum-like theories. Time allowing, I will also discuss how these results clarify which additional assumptions must be accepted if one wishes to seriously consider classical alternatives to quantum gravity.
会場: 研究本館 4階 445-447号室 / via Zoom
イベント公式言語: 英語
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セミナー
Classical Spinning Black Hole Scattering from Quantum Amplitudes
2026年1月15日(木) 14:00 - 15:30
Dogan Akpinar (Ph.D. Student, Higgs Centre for Theoretical Physics, School of Physics and Astronomy, University of Edinburgh, UK)
Scattering amplitudes have recently become a powerful tool for extracting classical observables in two-body gravitational dynamics, with direct relevance for current and future gravitational-wave experiments. In this talk, I will review how quantum scattering amplitudes can be used to obtain classical black hole scattering observables. A key focus will be the inclusion of spin effects, modelled by treating black holes as point particles in fixed-spin representations. This approach introduces a subtle ambiguity in the separation between classical and quantum information, which we resolve using our spin interpolation method. Leveraging this, we obtain, for the first time, the classical two-loop amplitude accurate to quartic order in spin, from which we extract physical observables such as linear and angular impulses using covariant Dirac brackets. Remarkably, the resulting amplitude obeys a spin-shift symmetry, remaining invariant under a shift of the black hole spin by the momentum transfer in the scattering process. Motivated by this structure, we examine the conserved quantities governing scattering and show that—at least asymptotically—the probe dynamics remain integrable through quartic order in spin. Under this asymptotic integrability, together with the spin-shift symmetry, we demonstrate that the quartic-in-spin radial action is fully determined by the aligned-spin sector. Taken together, these results advance our understanding of spinning black hole scattering and illuminate new structural features of Kerr dynamics.
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 明日開催
LEVERAGING EARTH OBSERVATIONS WITH MACHINE-LEARNING APPROACHES FOR WATER CYCLE MONITORING
2026年1月13日(火) 10:30 - 12:00
Victor Pellet (Professor, Laboratoire de Météorologie dynamique (LMD-X), Ecole Polytechnique, France)
Earth observation satellites provide unprecedented information to monitor the different components of the water cycle, from soil moisture to river dynamics. However, fully exploiting these observations remains challenging due to sensor limitations, data heterogeneity, complex physical processes, and spatio-temporal resolution constraints. This seminar provides an overview of machine-learning approaches that accompany and enhance remote sensing for water cycle analysis. It illustrates how statistical and machine-learning techniques can improve the exploitation of Earth observation (EO) data at different processing levels, from Level 1 to Level 4. Four examples are presented: (i) compressing hyperspectral information to reduce observation dimensionality, (ii) improving the retrieval of soil moisture from space by exploiting spatial patterns and handling missing data, (iii) harmonizing multi-source EO at the global scale for consistent water cycle monitoring, and (iv) modeling river dynamics using data-driven approaches. Together, these examples highlight the potential of machine-learning techniques to better integrate observations and improve our understanding of hydrological processes.
会場: 計算科学研究棟
イベント公式言語: 英語
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セミナー
Median-based estimators for randomized quasi-Monte Carlo integration
2026年1月9日(金) 15:00 - 17:00
鈴木 航介 (山形大学 准教授)
High-dimensional numerical integration is a ubiquitous challenge across various fields, from mathematical finance to computational physics and Bayesian statistics. While standard Monte Carlo (MC) methods are robust, their probabilistic error convergence rate of $O(N^{-1/2})$ is often insufficient for demanding applications. In this talk, I will introduce Quasi-Monte Carlo (QMC) and Randomized QMC (RQMC) methods, which offer a powerful framework for accelerating integration using low-discrepancy point sets. A key advantage of this deterministic approach is its ability to achieve a convergence rate of $O(N^{-1+\epsilon})$, significantly outperforming the standard MC rate. The second part of the talk will focus on the construction of point sets, specifically lattice rules and digital nets. I will explain how these methods achieve higher-order convergence rates, faster than $O(N^{-1})$, for sufficiently smooth integrands. I will also discuss their randomized variants and demonstrate how RQMC with mean-based estimators provides practical error estimation while maintaining high-order convergence. Finally, I will discuss recent progress in RQMC involving median-based estimators. I will highlight how these estimators achieve almost optimal convergence rates for various function spaces without requiring prior knowledge of the integrand.
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
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
Topological Image Analysis
2025年12月25日(木) 12:00 - 13:00
鍛冶 静雄 (九州大学 マス・フォア・インダストリ研究所 教授 / 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) 教授)
Topological Data Analysis (TDA) applies algebraic topology to the study of data such as point clouds. When applied to image and volumetric data, TDA provides a way to capture the topological features that characterise shapes and spatial structures. In this talk, I will outline the strengths and limitations of TDA for image analysis, and compare its capabilities with those of deep neural networks. I will also present hands-on examples using our open-source software Cubical Ripser. Finally, I will highlight a new direction in the use of TDA for image processing.
会場: SUURI-COOL (Kyushu) C501（九州大学 伊都キャンパス West 1号館 D棟） (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
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
Neural Network Quantum States for Quarkonium in Medium: Real-Time Open Quantum-System Dynamics
2025年12月19日(金) 16:00 - 17:00
Tom Magorsch (Ph.D. Student, Department of Physics, Technical University of Munich, Germany)
Many phenomena in high energy physics can not be described by Euclidean-time Monte Carlo estimates alone, but require genuine real-time evolution and a treatment of non-equilibrium effects. However, such simulations are computationally challenging. One such example is the evolution of heavy quarkonium in the quark gluon plasma produced in heavy-ion collisions. In this talk, I will introduce the open quantum system treatment of in-medium quarkonium. I will then give an overview on neural network quantum states as a variational approach to the real-time simulation of open quantum systems. As a controlled benchmark system, I will study the application to the Caldeira-Leggett model and conclude with an outlook on future applications of neural network based simulation of quarkonia in medium.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Two-component dark matter scenario in a pseudo-Nambu-Goldstone dark matter model - Tomohiro Abe
2025年12月18日(木) 14:00 - 15:30
阿部 智広 (名古屋大学 素粒子宇宙起源研究所 (KMI) 特任助教)
The WIMP dark matter (or thermal dark matter) is one of the leading candidates for dark matter and is widely studied. On the other hand, recent progress in direct detection experiments places severe constraints on WIMP dark matter models. Pseudo-Nambu-Goldstone boson dark matter models (pNG DM models) can explain the measured value of the dark matter energy density via the freeze-out mechanism and also naturally suppress the dark matter-nucleon scattering. The amplitudes for the processes are proportional to the momentum transfer squared from the dark sector to the visible sector; It is suppressed by t ~ 0 for the dark matter-nucleon scattering process, while it is proportional to s ~ 4 m_DM^2 for annihilation processes. The simplest realization faces the domain wall problem and needs to be extended. Several models have been proposed, but each model brings other issues, a large hierarchy in new energy scales, parameter tunings, and a Landau pole of a new gauge coupling. In this talk, I would like to propose a new pNG DM model based on SU(2)_gauge times SU(2)_global symmetry that overcomes those issues. The model predicts a two-component DM scenario, where one is pNG, and the other is an ordinary WIMP. I will show that the effective spin-independent cross section in the direct detection experiments is smaller than the current upper bound and larger than the prospect of the Darwin project in a wide range of parameter space in the two-component DM scenario.
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
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
A bi-fidelity Asymptotic-Preserving Neural Network approach for multiscale kinetic problems
2025年12月17日(水) 11:00 - 12:00
Liu Liu (Assistant Professor, Department of Mathematics, The Institute of Mathematical Sciences, The Chinese University of Hong Kong, Hong Kong)
In this talk, we will introduce a bi-fidelity Asymptotic-Preserving Neural Network (BI-APNNs) framework, designed to efficiently solve forward and inverse problems for the linear Boltzmann equation. Our approach builds upon the previously studied Asymptotic-Preserving Neural Network (APNNs), which employs a micro-macro decomposition to handle the model’s multiscale nature. We specifically address a bottleneck in the original APNNs: the slow convergence of the macroscopic density in the near fluid-dynamic regime. This strategy significantly accelerates the training convergence as well as improves the accuracy of the forward problem solution, particularly in the fluid-dynamic limit. We show several numerical experiments on both linear Boltzmann and the Boltzmann-Poisson system that this new BI-APNN method produces more accurate and robust results for forward and inverse problems compared to the standard APNNs. This is a joint work with Zhenyi Zhu and Xueyu Zhu.
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
928 イベント