セミナー
766 イベント
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セミナー
Particle acceleration in relativistic astrophysical plasmas
2024年12月13日(金) 14:00 - 15:15
カミリア・デミデム (理化学研究所 数理創造プログラム (iTHEMS) 研究員)
Relativistic astrophysical objects often display evidence of very efficient particle acceleration, such as X-ray and gamma-ray nonthermal emission and are widely recognized as potential sources of cosmic rays. Elucidating the physical mechanisms that turn these environments into such formidable particle accelerators is a longstanding problem of high-energy astrophysics. In this talk, I will briefly explain why shocks and turbulence, naturally expected to occur in these environments, could play an essential role in the acceleration of particles. I will then discuss some of the challenges that poses the description of these nonlinear processes, especially in the context of high-energy astrophysical sources, which involve astronomical ranges of scales and physical conditions much more extreme than we can probe in our laboratories or in the Solar system. Finally, I will share some recent results from my simulations.
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
Recent Advances in the Spectral Geometry of Domains and Approaches with Computer-Assisted Proofs
2024年12月12日(木) 15:00 - 17:00
遠藤 凌輝 (新潟大学 大学院自然科学研究科 数理物質科学専攻 博士課程)
What can we determine about the shape of a drum from its sound?"—This inverse problem has given rise to spectral geometry and has attracted researchers for over 110 years. The first half of the talk explains recent advances in shape optimization problems for domains with respect to eigenvalues of the Laplacian and the inverse problem known as "hearing the shape of a drum," presented in an accessible manner for experts from other disciplines. The second half introduces verified computation methods for eigenvalues, eigenfunctions, and shape derivatives. As applications, it presents newly established computer-assisted proofs for the minimization problem of eigenvalues with non-homogeneous Neumann boundary conditions, and the conjecture on the simplicity of the second Dirichlet eigenvalues for non-equilateral triangles.
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
Mechanism for Converting Temporal Rhythms into Spatial Patterns of Body Segment
2024年12月12日(木) 13:00 - 14:00
瓜生 耕一郎 (東京科学大学 生命理工学院 准教授)
In development, spatially periodic structures are spontaneously formed in various tissues. These developmental structures are also formed in a proper temporal order. How is such spatial and temporal coordination achieved in morphogenesis? In this presentation, we discuss the mechanism that translates temporal rhythms of gene expression into spatially periodic patterns in vertebrate body segment formation. Mechanisms for converting oscillatory signals into vertebrate body segments have been proposed previously. Cooke and Zeeman 1976 proposed the Clock and Wavefront model based on the concept of the catastrophe theory. Still, it remains unclear how this conceptual model actually works in embryos. Here we develop a mathematical model aided by recent imaging and molecular genetics data and reveal a spatiotemporal bifurcation structure for vertebrate segment formation by using the dynamical systems theory.
会場: セミナー室 (359号室) / via Zoom
イベント公式言語: 英語
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セミナー
How Neural Networks reduce the Fermionic Sign Problem and what we can learn from them
2024年12月11日(水) 15:30 - 16:30
Johann Ostmeyer (Post-doctoral Fellow, Helmholtz-Institut für Strahlen- und Kernphysik, University of Bonn, Germany)
When simulating fermionic quantum systems, non-perturbative Monte Carlo techniques are often the most efficient approach known to date. However, beyond half filling they suffer from the so-called sign problem, i.e. negative "probabilities", so that stochastic sampling becomes infeasible. Recently, considerable progress has been made in alleviating the sign problem by deforming the integration contour of the path integral into the complex plane and applying machine learning to find near-optimal alternative contours. In this talk, I am going to present a particularly successful architecture, based on complex-valued affine coupling layers. Furthermore, I will demonstrate how insight gained from the trained network can be used for simpler analytic approaches.
会場: via Zoom / 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
Simulating Parton Fragmentation on Quantum Computers
2024年12月11日(水) 13:30 - 15:00
ティエンイン・リー (Ph.D. Student, Institute of Quantum Matter, South China Normal University, China)
Parton fragmentation functions (FFs) are indispensable for understanding processes of hadron production ubiquitously existing in high-energy collisions, but their first principle determination has never been realized due to the insurmountable difficulties in encoding their operator definition using traditional lattice methodology. We propose a framework that makes a first step for evaluating FFs utilizing quantum computing methodology. The key element is to construct a semi-inclusive hadron operator for filtering out hadrons of desired types in a collection of particles encoded in the quantum state. We illustrate the framework by elaborating on the Nambu-Jona-Lasinio model with numeral simulations. Remarkably, We show that the semi-inclusive hadron operator can be constructed efficiently with a variational quantum algorithm. Moreover, we develop error mitigation techniques tailed for accurately calculating the FFs in the presence of quantum noises. Our work opens a new avenue for investigating QCD hadronization on near-term quantum computers.
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
Studying quark-gluon plasma with multi-stage dynamical models in relativistic nuclear collisions
2024年12月10日(火) 15:30 - 17:00
金久保 優花 (理化学研究所 数理創造プログラム (iTHEMS) 特別研究員)
A collision of relativistically accelerated large nuclei creates the hottest matter on Earth — quark-gluon plasma (QGP). The properties of QGP have been studied through comparisons of final-state particle distributions between theoretical models and experimental data. To quantitatively constrain QGP properties, it is necessary to build Monte Carlo models that simulate the space-time evolution of the system throughout the entire collision process. This includes the initial matter production from the accelerated nuclei, the evolution of QGP, hadronisation, and the evolution of hadron gas. In this talk, I will first explain how theoretical models, based on relativistic hydrodynamics and hadronic transport, are conventionally built and how they successfully extract QGP properties. Next, I will discuss a hot topic: the possibility of finding QGP in proton-proton collisions, based on results from a state-of-the-art model that includes both equilibrated and non-equilibrated systems. Also, I will introduce a novel Monte Carlo initial state model based on perturbative QCD minijet production supplemented with a saturation picture. This Monte-Carlo EKRT model is one of the first initial state models for hydrodynamics to describe initial particle production from small to large momentum within a single framework, where total energy-momentum and charge conservations are imposed.
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
Entanglement of astrophysical neutrinos
2024年12月10日(火) 13:30 - 15:00
Baha Balantekin (Eugene P. Wigner Professor, Department of Physics, University of Wisconsin-Madison, USA)
Collective oscillations of neutrinos represent emergent nonlinear flavor evolution phenomena instigated by neutrino-neutrino interactions in astrophysical environments with sufficiently high neutrino densities. In this talk, after a brief introduction, it will be shown that neutrinos exhibit interesting entanglement behavior in simplified models of those oscillations. Attempts to study this behavior using classical and quantum computers will be described. An intriguing connection to the heavy-element nucleosynthesis, namely the possibility of neutrino entanglement driving a new kind of i-process nucleosynthesis, will be introduced,
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
Dark matter from inflationary quantum fluctuations
2024年12月9日(月) 14:00 - 15:30
Mohammad Ali Gorji (Junior Faculty, Center for Theoretical Physics of the Universe, Institute for Basic Science, Republic of Korea)
We explore a scenario in which dark matter is a massive bosonic field, arising solely from quantum fluctuations generated during inflation. In this framework, dark matter exhibits primordial isocurvature perturbations with an amplitude of O(1) at small scales that are beyond the reach of current observations, such as those from the CMB and large-scale structure. Assuming a monochromatic initial power spectrum, we identify the viable parameter space defined by dark matter mass and the length scale of perturbations. A key prediction of this scenario is copious formation of subsolar dark matter halos at high redshifts.
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
The Long Road towards Quantum Simulations of the Standard Model
2024年12月6日(金) 11:00 - 12:00
Dorota Grabowska (Research Assistant Professor, InQubator for Quantum Simulations (IQuS), University of Washington, USA)
The Standard Model of Particle Physics, encapsulating the vast majority of our understanding of the fundamental nature of our Universe, is at its core a gauge theory. Much of the richness of its phenomenology can be traced back to the complicated interplay of its various gauged interactions. While massive theoretical and algorithmic developments in classical computing have allowed us to probe many of these aspects, there remain a plethora of open questions that do not seem amenable to these methods. With a fundamentally different computational strategy, quantum computers hold the potential to address these open questions. However, a long road lies ahead of us before this potential may be realized. In this talk, I discuss a key step on this journey: constructing lattice gauge Hamiltonians that can be efficiently simulated on digital quantum devices. In particular, I focus on recent work that develops a fully gauge fixed Hamiltonian for SU(2) without fermions. Not only is this formulation well-suited for "close to continuum" simulations, it is also significantly less non-local than might be initially expected.
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
Bacterial ecospecies and ecoclines
2024年12月5日(木) 16:00 - 17:00
Daniel Falush (Professor, Shanghai Institute of Immunity and Infection, Chinese Academy of Sciences, China)
All bacteria reproduce clonally but some species exchange DNA frequently enough that they have well mixed geographic gene pools, similar to those found in outbreeding animals and plants. Using data from multiple species we show that these “recombinogenic” bacteria also have genome-wide genetic structures generated by natural selection, including discrete “ecospecies” and continuous “ecoclines”. These structures reflect evolutionary strategies employed within natural populations, which can be dissected using the powerful techniques of molecular microbiology, providing a unique new view into the private lives of bacteria.
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
Deep Learning for Non-Perturbative Quantum Chromodynamics
2024年12月4日(水) 15:00 - 16:30
Fu-Peng Li (PhD Candidate, Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, China)
Machine learning, particularly deep learning, is revolutionizing research across diverse disciplines, including physics. In this seminar, we explore the application of deep learning techniques to tackle challenges in non-perturbative Quantum Chromodynamics (QCD), one of the most complex areas in fundmental physics. I will present our preliminary explorations in this interdisciplinary field, focusing on: (i) identifying the equations of state for nuclear matter, (ii) developing a neural network-based quasi-particle model for QCD equations of state, (iii) extracting parton fragmentation functions, and (iv) determining heavy quark interaction potentials. Fu-Peng Li s a Ph.D. candidate in Theoretical Physics at Central China Normal University(CCNU) with an expected graduation in June 2025. His research interests lie at the intersection of nuclear physics and machine learning, with a focus on auto-differentiation, physics-informed neural networks (PINNs) for inverse problems, and the application of machine learning to non-perturbative Quantum Chromodynamics (QCD).
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
Global Thermodynamics for Heat Conduction Systems
2024年12月2日(月) 14:00 - 15:30
中川 尚子 (茨城大学 理工学研究科 教授)
Non-equilibrium phenomena are typically addressed through continuum descriptions based on local equilibrium and linear response theory, such as hydrodynamics. While effective, these approaches often overlook global characteristics. We propose Global Thermodynamics as a minimal-variable framework to describe weak non-equilibrium systems, focusing on two-phase coexistence under weak heat flux. By introducing a unique global temperature and extending entropy to non-equilibrium systems with a non-additive term, the framework predicts phenomena like metastable state stabilization—beyond the scope of traditional heat conduction equations. This talk will outline the framework, its key predictions, and validation efforts through numerical simulations and experiments. (This is a joint seminar with Informatin Theory Study Group.)
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
White dwarf binary stars as physics laboratories
2024年11月29日(金) 14:00 - 15:15
ルーシー・マクニール (理化学研究所 数理創造プログラム (iTHEMS) 特別研究員)
White dwarfs are the most common remnant of stellar evolution, and most often orbit a binary companion. Orbital decay from gravitational radiation and binary stellar evolution can proceed to mass transfer onto the white dwarf, which may result in a Type Ia supernova. While these reliable thermonuclear explosions are essential tools for observational cosmology, the nature of the progenitor binary (double white dwarf, or white dwarf + evolved star) is still not clear. Surprisingly, recent galaxy surveys revealed that most Type Ia supernova come from exploding white dwarfs below the Chandrasekhar limit of 1.4 solar mass. Plus, observations of Milky Way white dwarf binaries suggest unexpectedly hot temperatures in double white dwarf merger progenitors. I will summarise our recent developments on the stellar structure and orbital evolution of finite temperature, partially degenerate white dwarfs in binary systems. Tidal heating can explain how candidate white dwarf merger progenitors are generically hot, which places more restrictive conditions required for a double white dwarf merger.
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
asymptotics in astrophysics SG session 4: helioseismology
2024年11月29日(金) 10:30 - 12:00
嶌田 遼太 (京都大学 大学院理学研究科 宇宙物理学教室 博士課程)
Constraining the distribution of internal magnetic fields through observations is considered to advance solar dynamo models aimed at understanding the 11-year cycle of solar magnetic activity. This paper [1] is on the frequency shift of standing acoustic waves inside the Sun caused by internal magnetic fields. Quasi-degenerate perturbation theory is applied to treat perturbation by magnetic fields. I’d like to discuss their methods and application in the session.
会場: セミナー室 (359号室) / via Zoom
イベント公式言語: 英語
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セミナー
Analysing and Visualising Single Cell Omits Data
2024年11月28日(木) 15:30 - 16:30
ドロシー・エリス (理化学研究所 生命医科学研究センター (IMS) 統合ゲノミクス研究チーム 特別研究員)
Single cell multimodal omics data are characterized by sparsity, noise, and high dimension. Incorporating information across modalities is challenging. We developed a non-negative matrix factorization based algorithm to identify latent factors that can facilitate improved cell-type clustering and visualizations for multimodal single cell omics count data. We then extend this algorithm to larger datasets and for different distributions of data in different modalities.
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
Crop domestication
2024年11月25日(月) 15:00 - 17:00
Cheng-Ruei Lee (Professor, Institute of Ecology and Evolutionary Biology, National Taiwan University, Taiwan)
ジェフリ・フォーセット (理化学研究所 数理創造プログラム (iTHEMS) 上級研究員)This is a joint seminar hosted by the Mathematical Biology lab of Kyushu University where Jeffrey Fawcett (iTHEMS) and Cheng-Ruei Lee (National Taiwan University) will give talks about plant domestication. Both talks will be aimed at students and will include some basic introduction of the topic. The seminar will be held on-site at Kyushu University and also by zoom so please free to register and join. Program: Title: Domestication and dispersal process of common buckwheat Speaker: Dr. Jeffrey Fawcett (RIKEN iTHEMS) Abstract: Crop domestication has not only been an ideal model to study how selection drives evolution, it is also tightly linked to past human activity and contains useful information that can improve plant breeding. Common buckwheat (Fagopyrum esculentum), which is used to make “soba” noodles in Japan, was domesticated from a wild progenitor species distributed in Southwest China. We have been using whole-genome sequences of several hundred cultivated accessions from around the world and some wild progenitor accessions to study its process of domestication and subsequent dispersal throughout Eurasia including Japan. In this talk, I will first provide an overview of the domestication and dispersal process of common buckwheat based on archaeological findings. I will then discuss the domestication and dispersal process and adaptive evolution of common buckwheat based on results of our population genetic analyses [1]. Title: The domestication and expansion history of mung bean and adzuki bean: evidence from population genomics Speaker: Prof. Cheng-Ruei Lee (National Taiwan University) Abstract: Who domesticated the crops we eat? When and where? What happened after domestication? How did crops spread across the world? These are the questions that have fascinated archaeologists for a long time. Using modern genomics techniques, we aim to answer these questions from a different angle. In mung bean (Vigna radiata), we uncovered a unique route of post-domestication range expansion. This route cannot be explained simply by human activities alone; instead, it is highly associated with the natural climates across Asia. We showed how the trans-continental climatic variability affected the range expansion of a crop and further influenced local agricultural practices and the agronomic properties of mung bean varieties. In adzuki (Vigna angularis), we obtained solid evidence of its domestication in Japan, most likely by the Jomons. We identified and validated the causal mutations for the seed coat color change during domestication. Contrary to the common belief that important yield-ensuring phenotypes (e.g., loss of pod shattering) should be selected early during domestication, we revealed a unique order of domestication trait evolution that cannot be observed from archaeological records directly [2]. Please register via the form by November 22nd (Fri.). We will share the Zoom link with online participants on the morning of the event day.
会場: 九州大学 伊都キャンパス W1-C-909 /
イベント公式言語: 英語
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セミナー
Solving inverse problem via latent variable optimization of diffusion models: An application to CT reconstruction
2024年11月25日(月) 14:00 - 15:00
尾崎 翔 (弘前大学 大学院理工学研究科 助教)
Inverse problems are widely studied in various scientific fields, including mathematics, physics, and medical imaging (such as CT and MRI reconstructions). In this talk, I will present a novel method for solving inverse problems using the diffusion model, with an application to CT reconstruction. The diffusion model, which is a core component of recent image-generative AI, such as Stable Diffusion and DALL-E3, is capable of producing high-quality images with rich diversity. The imaging process in CT (i.e., CT reconstruction) is mathematically an inverse problem. When the radiation dose is reduced to minimize a patient's exposure, image quality deteriorates due to information loss, making the CT reconstruction problem highly ill-posed. In the proposed method, the diffusion model, trained with a large dataset of high-quality images, serves as a regularization technique to address the ill-posedness. Consequently, the proposed method reconstructs high-quality images from sparse (low-dose) CT data while preserving the patient's anatomical structures. We also compare the performance of the proposed method with those of other existing methods, and find that the proposed method outperforms the existing methods in terms of quantitative indices.
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
Theoretical analysis of High-dose/Refuge strategy for durability of pest control
2024年11月21日(木) 16:00 - 17:00
鈴木 清樹 (総合研究大学院大学 統合進化科学研究センター 博士研究員)
When using chemicals to control pathogens or pests, a problem that always arises is that parasites develop resistance to the chemicals. In many cases, the amount of chemical used must be reduced for using the chemicals sustainably. However, if certain conditions are met, a method is known that can suppress the development of resistance in diploid organisms such as pest insects. This is the high-dose/refuge strategy (HD/R) proposed by Comins (1977). This unique method combines high doses of pesticide spraying with ‘Refuge’ that are completely pesticide-free, and is a rare example of a successful method that actually fields. In this presentation, I will provide an overview of the HD/R strategy, a formulation that incorporates the entire life cycle of the insect, which was an issue that Comins had not yet resolved. And show the life cycle of the insect and the conditions under which the HD/R strategy is effective, based on the results of an approximation using a source-think model.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Nuclear clustering phenomena revealed by knockout reaction
2024年11月20日(水) 15:30 - 17:00
吉田 数貴 (大阪大学 核物理研究センター 助教)
Nuclear clustering is one of the unique phenomena in the nucleon many-body system. Historically, alpha formation has been known since the very early years of the nuclear physics, in the light and heavy mass regions. The former is known as the alpha clustering and its threshold rule, which was introduced by the Ikeda diagram in 1968. The latter has been known since the beginning of the nuclear physics as the alpha decay phenomena; the formation of alpha particles and their tunneling through the Coulomb barrier. Recently, the alpha clustering has been experimentally confirmed in the medium mass nuclei, 112-124Sn (Tin isotopes), using the alpha knockout reaction. Triggered by the experimental observation, the alpha knockout reaction is used as a reaction probe for the alpha clustering phenomena. In this talk, I will give an overview of the clustering phenomena and its reaction observables, in particular I will introduce the idea that the alpha knockout reaction can be a probe for the alpha formation on the alpha decay nuclei. In general, this idea can be applied to probe the particle trapped in the potential resonance.
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
766 イベント