Featured News
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Four Perspectives on Neutron Stars, Pulsars, and Magnetars
The recent work [1] on X-ray bursts from the neutron stars led by our colleague, Akira Dohi (Visiting Scientist, iTHEMS), was featured in the article "Four Perspectives on Neutron Stars, Pulsars, and Magnetars" appeared in Research highlights from the Journals of the American Astronomical Society (see related link below).
2022-12-05
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極低温の量子流体中に現れる普遍的な力 －量子揺らぎが導く原子超流動体中の分子間力－
万有引力の法則に代表されるように、「物質間に働く力」という概念は、物理学において重要な位置を占め続けてきました。新潟大学 自然科学系（理学部）の本郷 優 助教（理化学研究所 数理創造プログラム 客員研究員）とドイツ・ハイデルベルク大学の藤井 啓資 研究員・Tilman Enss 教授の国際共同研究グループは、極低温の量子流体中に浮かべられた粒子間に、長距離ではファンデルワールス力と呼ばれる分子間力と同じ力が働くことを理論計算から明らかにしました。レーザー技術によって絶対零度近く（数十ナノケルビン程度）まで冷却された原子集団は、量子状態を高精度に制御可能な系として近年注目されており、ミクロな世界における力を調べる上でも格好の舞台となっています。本研究は、極低温で実現する原子超流動体中の不純物粒子に、量子揺らぎに起因した普遍的な長距離力が作用することを新たに明らかにしたものです。 詳細は下記の関連リンクより新潟大学のホームページをご覧ください。
2022-12-02
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Naritaka Oshita presented his talk at the 12th Koshien of Science (Oita tournament) on November 3, 2022
The 12th Koshien of Science (Oita tournament), a scientific competition for high school students in Oita prefecture, was held on 3rd November 2022 at Oita city. Naritaka Oshita from iTHEMS presented his talk on “Black Holes Veiled in Mystery” after the competition. More than 200 high school students from Oita prefecture attended. Oshita talked about the history of science, recent progress, and remaining mysteries of black holes. A student asked a unique question “What if we fall into a black hole? Can our consciousness be recovered from the hole?”. Another student asked, “How can it be possible to detect the signal from a ringing black hole?”. The audience enjoyed the stimulating talk and questions from the students. During the competition, Oshita and an iTHEMS assistant Tomoko Iwanami observed the competition, where some students built their toy cars in each group and competed in a race.
2022-11-10
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Science Agora 2022 is held November 4-6, 2022
Science Agora 2022 is held online and in person in the period Nov. 4-6, 2022. There will be many fun sessions that you can join in person or online. There are English sessions too. RIKEN will have a session "Envisioning Futures: Navigating the research landscape with senior women researchers" in which Tetsuo Hatsuda from iTHEMS is one of the speakers. Enjoy !
2022-11-04
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クォーク物質を重力波で探る－中性子星合体後の重力波から超高密度物質の痕跡を読み取る－
理化学研究所（理研）数理創造プログラムのホワン・ヨングジア研修生、開拓研究本部長瀧天体ビッグバン研究室の長瀧重博主任研究員（理研数理創造プログラム副プログラムディレクター）、大阪大学インターナショナルカレッジのバイオッティ・ルカ准教授、東北大学大学院理学研究科の古城徹准教授らの国際共同研究グループは、連星中性子星の合体に対して一般相対性理論に基づいた数値シミュレーションを行い、合体後に放出される重力波の波形から1cm<sup>3</sup>当たり1兆kgを超える超高密度物質の性質が詳細に読み取れることを示しました。 本研究成果は、重力波天文学において、中性子星の内部構造や超高密度物質の性質の解明に貢献すると期待できます。 詳細は、関連リンクをご覧ください。
2022-10-27
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The RIKEN-Berkeley Center was featured in RIKEN Overseas Office Newsletter
The RIKEN-Berkeley Center was featured in the Oct. 2022 issue of "News from RIKEN's Overseas Offices". The title of the article written by Adam Phillips in the RIKEN International Affairs Division is "What makes institutional international collaborations work?". Enjoy the article!
2022-10-25
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Featured articles on iTHEMS published in "Sugaku Tsushin"
iTHEMS was featured in the August volume of "Sugaku Tsushin" (Japanese magazine published by The Mathematical Society of Japan). Our colleagues, Tetsuo Hatsuda, Ade Irma Suriajaya, Yosuke Kubota, Hiroyasu Miyazaki and Yukimi Goto, have written essays on iTHEMS in the volume. Let's see mathematicians' thoughts on the iTHEMS atmosphere.
2022-08-30
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新型コロナウイルス感染者の隔離短縮は可能か？－隔離終了タイミング検証のシミュレータを開発－
国立大学法人東海国立大学機構 名古屋大学大学院理学研究科の岩見真吾教授（兼理化学研究所数理創造プログラム客員研究員）は、米国インディアナ大学の江島啓介助教らとの共同研究で、抗原検査により新型コロナウイルス（COVID-19）感染者の隔離を終了するタイミングを検証するためのシミュレータ（シミュレーションのためのソフトウエア）を新たに開発しました。 これにより、決められた回数の抗原検査の陰性結果をもって、早期にCOVID-19感染者の隔離を終了できる、柔軟で安全な隔離戦略が提案できるようになります。 感染者隔離は感染拡大を防ぐ重要な手段です。長期にわたる隔離は二次感染のリスクを下げる一方で、隔離される人やそれを支える社会も様々な負担を被ります。 研究グループは、開発したシミュレータを用いて、"感染性のある患者の隔離を（早く）終了してしまうリスク"と"感染性を失った患者を不要に隔離してしまう期間（隔離に関わる負担）"の計算に成功しました。この結果、リスクと負担を同時に抑えるための個人差を考慮した適切な隔離戦略を、抗原検査を用いて実施する方法を提案できるようになりました。感染予防対策を徹底しつつ社会活動を再開・維持するウィズコロナの時代を迎えるにあたり、抗原検査をうまく利用することで教育活動や社会活動を安全に実施することができるようになります。 現在、臨床・疫学データや経験則に基づいた異なる隔離基準が国ごとに採用されている状況に対して、本研究は、数理モデルに基づいた、日本のみならず世界的に求められている柔軟な隔離ガイドラインの確立に貢献できると期待されます。 詳細は関連リンクより名古屋大学 研究成果発信サイトをご覧ください。
2022-08-29
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RIKEN Research: Applying quantum speed limits to macroscopic systems
An expression for the maximum speed at which changes in macroscopic systems can occur has been derived by a theoretical physicist at RIKEN. This will deepen our understanding of quantum phenomena in systems that are not in equilibrium. One of the hardest aspects of quantum mechanics to grasp is the Heisenberg uncertainty principle that states that it is not possible to simultaneously pin down both the position and momentum of an object. In other words, the more precisely a particle’s position is determined, the broader the range of its possible momentum becomes (and vice versa). In 1945, two physicists, Leonid Mandelstam and Igor Tamm, focused on another type of the uncertainty relation, namely one between time and energy fluctuation, and showed that transitions in quantum systems don’t happen instantaneously; rather, the speed at which a transition occurs is capped by an amount determined by how much the energy of the system fluctuates. Many other so-called quantum speed limits have subsequently been derived, which have helped better understand the physics of quantum systems and have been useful in various quantum applications. But big problems arise when quantum speed limits are applied to macroscopic systems. “Previous quantum speed limits, which are useful for small systems, typically become meaningless for macroscopic transitions,” notes Ryusuke Hamazaki of the Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team. “For example, conventional quantum speed limits give an infinite upper bound for the speed of transitions in a gas made up of atoms.” To read more, please visit the related link.
2022-08-26
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大分STEMフェスタが大分市で開催されました
2022年7月23日に大分STEMフェスタが大分市で開催され、iTHEMSから初田哲男ディレクターが参加し、（株）ADKと協力して、Bコース「ブラックホール・レコーダーで1000年後にメッセージを届けよう」において、５０名を越える大分県各地から集まった高校生にブラックホールの解説と、Useless Prototyping Studioで制作したブラックホールレコーダーの実演を行いました。 また、情報ストレージとしてのブラックホールに、未来に託す俳句を記録する内容を高校生同士で話し合い、最近撮像されたブラックホール写真に書き込んでもらいました。 大分STEMフェスタには１５０名を越える高校生が参加し、Aコース「月面ローバー体験をしよう！」、Bコース「ブラックホール・レコーダーで1000年後にメッセージを届けよう」、Cコース「VR技術×社会の課題解決×SDGs」、Dコース「大分の未来に必要な仕事を考えよう」に分かれて、たいへん有意義な一日を過ごしました。iTHEMSからは、初田プログラムディレクターに加えて、アシスタントの和田ひとみさんと太田千賀子さんが現地でBコース開催に貢献されました。
2022-08-22
Videos
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気候変動って実際どうなの？【ヨビノリ×研究者】
Odd couples of interdisciplinary research
Khovanov homology theory - an introduction to categorification by Dr. Taketo Sano on May 13, 2022
ファンダメンタルズ フェスmini プレイベント 科学篇 「探究と架橋：基礎科学の可能性」
Pcペンタクォークをもとめて―「富岳」でハドロン間相互作用を探る
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理化学研究所 2019
A new B.O.A.T. in astrophysics
Evolution and our daily rhythms
Area law of entanglement entropy in quantum many body systems and its implication in tensor network calculation
Comparison between conventional computers and quantum computers
数理創造プログラム（Interdisciplinary Theoretical and Mathematical Sciences Program, 略称 iTHEMS アイテムズ）は、理論科学・数学・計算科学の研究者が分野の枠を越えて基礎研究を推進する、理化学研究所の新しい国際研究拠点です。iTHEMSでは、「数理」を軸とする分野横断的手法により、宇宙・物質・生命の解明や、社会における基本問題の解決を目指しています。
Upcoming Events
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セミナー 本日開催Carrollian hydrodynamics near the black hole horizon
2022年12月8日(木)16:00 - 17:30
プトゥラク・ジャイアクソナ (数理創造プログラム 特別研究員)
The membrane paradigm provides a fascinating bridge between gravitational dynamics near black hole horizons (null boundaries) and fluid dynamics. One question naturally follows: what type of fluids and hydrodynamics emerged at the horizon? Contrary to the longstanding belief, it turns out that the horizon fluid is Carrollian, rather than the Galilean (Navier-Stokes) fluid. The Carroll geometries and Carrollian physics, arising originally when the speed of light goes to zero (c to 0 limit), have recently gained increasing attention in the fields of black hole physics and flat holography. In this presentation, I will talk about the Carrollian limit and the resulting Carroll geometries and this unusual kind of hydrodynamics, the Carrollian hydrodynamics. I will then present the geometrical construction of the membrane (also known as the stretched horizon) in a way that a Carroll geometry manifest, therefore allowing us to spell out precisely the dictionary between gravitational degrees of freedom on the membrane and the Carrollian fluid quantities. I will also show that the Einstein’s equations projected onto the horizon are the Carrollian hydrodynamic conservation laws. Lastly, I will discuss the covariant phase space of the horizon, symmetries, and conservation laws. The talk is based on arXiv:2209.03328 and arXiv:2211.06415.
会場: コモンルーム 246-248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
Quantum kinetics of neutrinos in high-energy astrophysical phenomena
2022年12月9日(金)14:00 - 15:00
長倉 洋樹 (国立天文台 科学研究部 特任助教（国立天文台フェロー）)
Neutrinos are the most mysterious and elusive particles in the standard model of particle physics. They play important roles in core-collapse supernovae and binary neutron star mergers as driving mass-ejection, synthesizing heavy elements including r-process nuclei, and neutrino signals from these sources. This exhibits the importance of accurate modeling of neutrino radiation field in these phenomena, which will be used to connect neutrino physics to multi-messenger astronomy. It has recently been suggested that neutrino-flavor conversion (or neutrino-oscillation) can ubiquitously occur in these astrophysical environments, exhibiting the requirement of quantum kinetic treatments in the modeling of neutrino transport. In this seminar, I will give an overview of the quantum kinetics neutrino transport and then introduce its recent progress, paying a special attention to the connection to astrophysics. I will also present the latest results of our numerical simulations of collective neutrino oscillations, which can be properly accounted for only by quantum kinetic framework.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Chiral effects on lepton transport in core-collapse supernovae
2022年12月13日(火)13:30 - 15:00
Dr. Di-Lun Yang (Assistant Research Fellow, Institute of Physics, Academia Sinica, Taiwan)
Dynamics of leptons such as electrons and neutrinos play an important role in the evolution of core-collapse supernovae (CCSN). Nevertheless, chirality as one of fundamental microscopic properties that could affect lepton transport, through e.g. weak interaction, has been mostly overlooked. In this talk, I will discuss how chiral effects such as the renowned chiral magnetic effect (CME), generating an electric charge current along magnetic fields with chirality imbalance, could result in the unstable modes of magnetic fields and inverse cascade, which potentially influence the matter evolution in CCSN and pulsar kicks. I will also show how an effective CME could be realized via the backreaction from neutrino radiation even in the absence of an axial charge characterizing an unequal number of right- and left-handed electrons.
会場: コモンルーム 246-248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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コロキウムThe Epidemiology and Economics of Physical Distancing during Infectious Disease Outbreaks
2022年12月14日(水)11:00 - 12:30
Prof. Troy Day (Professor, Head of Department, Department of Mathematics and Statistics, Queen's University, Canada)
People's incentives during an infectious disease outbreak influence their behaviour, and this behaviour can impact how the outbreak unfolds. Early on during an outbreak, people are at little personal risk of infection and hence may be unwilling to change their lifestyle to slow the spread of disease. As the number of cases grows, however, people may then voluntarily take extreme measures to limit their exposure. Political leaders also respond to the welfare and changing desires of their constituents, through public health policies that themselves shape the course of the epidemic and its ultimate health and economic repercussions. In this talk I will use ideas from the study of differential games to model how individuals’ and politicians’ incentives change during an outbreak, and the epidemiological and economic consequences that ensue when these incentives are acted upon. Motivated by the COVID-19 pandemic, I focus on physical distancing behaviour and the imposition of stay-at-home orders by politicians. I show that there is a fundamental difference in the political, economic, and health consequences of an infectious disease outbreak depending on the degree of asymptomatic transmission. If transmission occurs primarily by asymptomatic carriers, then politicians will be incentivized to impose stay-at-home orders earlier and for longer than individuals would like. Despite such orders being unpopular, however, they ultimately benefit all individuals. On the other hand, if the disease is transmitted primarily by symptomatic infections, then individuals are incentivized to stay at home earlier and for longer than politicians would like. In this case, politicians will be incentivized to impose back-to-work orders that, despite being unpopular, will again ultimately be to the benefit of all individuals. This is joint work with David McAdams, Fuqua School of Business and Economics Department, Duke University.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Lattice gauge theory in curved spacetimes
2022年12月15日(木)14:00 - 15:30
山本 新 (東京大学 大学院理学系研究科 物理学専攻 助教)
Lattice gauge theory is a powerful computational approach in quantum field theory. It is also utilizable for investigating quantum phenomena in curved spacetimes, such as rotating frame, torsion, and gravitational backgrounds. In this talk, I would like to overview the formulation and results of lattice simulations in curved spacetimes.
会場: コモンルーム (246-248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
Chemophoresis Engine: Theory of ATPase-driven Cargo Transport
2022年12月15日(木)16:00 - 17:00
菅原 武志 (東京大学 生物普遍性研究機構 特任研究員)
The formation of macromolecule patterns depending on chemical concentration under non-equilibrium conditions, first observed during morphogenesis, has recently been observed at the intracellular level, and its relevance as intracellular morphogen has been demonstrated in the case of bacterial cell division. These studies have discussed how cargos maintain positional information provided by chemical gradients. However, how cargo transports are directly mediated by chemical gradients remains unknown. Based on the previously proposed mechanism of chemotaxis-like behavior of cargos (referred to as chemophoresis), we introduce the chemophoresis engine as a physicochemical mechanism of cargo motion, which transforms chemical free energy to directed motion through the catalytic ATP hydrolysis [1]. We propose its possible role as a universal principle of hydrolysis-driven intracellular transport.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Geometric decomposition of entropy production in stochastic and chemical systems
2022年12月16日(金)13:30 - 15:00
吉村 耕平 (東京大学 大学院理学系研究科 物理学専攻 博士課程)
Entropy production is central to understanding nonequilibrium phenomena. It is known that decomposing entropy production enables us to separately treat distinct two aspects of dynamics, nonstationarity and breaking of detailed balance. In this seminar, I talk about our recent progress on geometric decomposition of entropy production in discrete stochastic systems and deterministic chemical systems. For the audience who may not be familiar with nonequilibrium thermodynamics and linear algebraic graph theory, which the latter enables us to treat the two kinds of systems at once, I would like to start with a very basic introduction. Then I explain why and how we decompose entropy production. Specifically, I mainly focus on the "Onsager-projective decomposition" we study in arXiv:2205.15227 rather than the information geometric decomposition provided in the following paper arXiv:2206.14599. Further, several physical consequences will be discussed, including generalization of Schnakenberg's decomposition stemming from cycles in a steady system, and its relation to gradient flow expressions of a master equation and a rate equation.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Understanding kilonova spectra and identification of r-process elements
2023年1月20日(金)14:00 - 15:00
土本 菜々恵 (東北大学 大学院理学研究科 天文学専攻 博士課程（学術振興会特別研究員）)
Binary neutron star (NS) merger is a promising site for the rapid neutron capture nucleosynthesis (r-process). The radioactive decay of newly synthesized elements powers electromagnetic radiation, as called kilonova. The detection of gravitational wave from a NS merger GW170817 and the observation of the associated kilonova AT2017gfo have provided with us the evidence that r-process happens in the NS merger. However, the abundance pattern synthesized in this event, which is important to understand the origin of the r-process elements, is not yet clear. In this talk, I will first introduce an overview and current understanding of kilonova. Then, I will discuss our recent findings of elemental features in photospheric spectra of kilonova toward identification of elements.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Physics-informed deep learning approach for modeling crustal deformation
2023年1月23日(月)10:30 - 12:00
上田 修功 (理化学研究所 革新知能統合研究センター (AIP) 副センター長)
The movement and deformation of the Earth’s crust and upper mantle provide critical insights into the evolution of earthquake processes and future earthquake potentials. Crustal deformation can be modeled by dislocation models that represent earthquake faults in the crust as defects in a continuum medium. In this study, we propose a physics-informed deep learning approach to model crustal deformation due to earthquakes. Neural networks can represent continuous displacement fields in arbitrary geometrical structures and mechanical properties of rocks by incorporating governing equations and boundary conditions into a loss function. The polar coordinate system is introduced to accurately model the displacement discontinuity on a fault as a boundary condition. We illustrate the validity and usefulness of this approach through example problems with strike-slip faults. This approach has a potential advantage over conventional approaches in that it could be straightforwardly extended to high dimensional, anelastic, nonlinear, and inverse problems.
会場: via Zoom
イベント公式言語: 英語
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コロキウムScaling Optimal Transport for High dimensional Learning
2023年1月24日(火)17:00 - 18:30
Dr. Gabriel Peyré (Research Director, CNRS/École Normale Supérieure, France)
iTHEMS-AIP Joint Colloquium Optimal transport (OT) has recently gained a lot of interest in machine learning. It is a natural tool to compare in a geometrically faithful way probability distributions. It finds applications in both supervised learning (using geometric loss functions) and unsupervised learning (to perform generative model fitting). OT is however plagued by the curse of dimensionality, since it might require a number of samples which grows exponentially with the dimension. In this talk, I will explain how to leverage entropic regularization methods to define computationally efficient loss functions, approximating OT with a better sample complexity. More information and references can be found on the website of our book "Computational Optimal Transport" (see related link below).
会場: via Zoom
イベント公式言語: 英語
Opportunities
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研究員または上級研究員募集（W22160）
締め切り: ポストが決まり次第
研究員または上級研究員 若干名。iTHEMSでは、宇宙物理学、天文学、宇宙論およびその関連分野（理論）の研究員または上級研究員を募集しています。iTHEMSの理念のもと、各自の研究テーマでトップレベルの研究を行うだけでなく、数学、物理学、化学、生物学、情報科学、計算科学、社会科学などにおける異分野連携をリードすることが期待されています。
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女性研究員または女性上級研究員募集（W22158）
締め切り: ポストが決まり次第
女性研究員または女性上級研究員 若干名。iTHEMSでは、自然科学、数理科学、人文・社会科学のいずれかの分野で理論研究を行う女性研究員または女性上級研究員を募集している。職責と職階は、応募者のこれまでのキャリアに応じて決定される。今回公募する研究員または上級研究員は、数学、数理科学、人文・社会科学などの分野において、トップレベルの理論研究を推進するとともに、iTHEMSのコンセプトのもとで、数学、物理学、化学、生命科学、工学、計算科学、情報科学、人文・社会科学などの分野にまたがる学際的な共同研究を行うことが期待されている。
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特別研究員募集（W22157）
締め切り: ポストが決まり次第
特別研究員 若干名。宇宙論（理論）の分野で活躍する研究者を、理研数理創造プログラムの特別研究員として募集します。特別研究員としての着任後は、当分野における研究を推進するのみならず、iTHEMSのメンバーとして、数学・物理学・化学・生命科学・工学・計算科学・情報科学・社会科学・深層学習などの多分野横断的研究の促進に意欲を持って取り組むことが期待されています。
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研究員または上級研究員募集（W22142）
締め切り: ポストが決まり次第
研究員または上級研究員 若干名。iTHEMSでは、量子計算科学、量子情報科学およびその関連分野の研究員または上級研究員を募集しています。iTHEMSの理念のもと、各自の研究テーマでトップレベルの研究を行うだけでなく、数学、物理学、化学、生物学、情報科学、計算科学、社会科学などにおける異分野連携をリードすることが期待されています。
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研究員または上級研究員募集（W22141）
締め切り: ポストが決まり次第
研究員または上級研究員 若干名。iTHEMSでは、理論情報科学あるいは応用情報科学、特に機械学習やデータ解析と関連する研究を行う研究員または上級研究員を募集しています。iTHEMSの理念のもと、各自の研究テーマでトップレベルの研究を行うだけでなく、数学、物理学、化学、生物学、情報科学、計算科学、社会科学などにおける異分野連携をリードすることが期待されています。
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研究員または上級研究員募集（W22140）
締め切り: ポストが決まり次第
研究員または上級研究員 若干名。iTHEMSでは、純粋数学、応用数学、産業数学などの数理科学分野の研究員または上級研究員を募集しています。iTHEMSの理念のもと、各自の研究テーマでトップレベルの研究を行うだけでなく、数学、物理学、化学、生物学、情報科学、計算科学、社会科学などにおける異分野間連携をリードすることが期待されます。今回は、数理科学の分野で高い能力を持つ若手研究者の応募を歓迎します。
Latest News
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2022-12-05
セミナーレポート
iTHEMS Math Seminar by Dr. Yosuke Matsuzawa on November 11, 2022
On November 11, there was a math seminar by professor Matsuzawa. He gave an introductory talk on the arithmetic dynamical system. He started from simple and interesting examples to some conjectures. Reported by Keita Mikami
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2022-12-05
セミナーレポートMath-Phys Seminar by Dr. Christy Koji Kelly on October 14, 2022
On October 14, there was a joint seminar by Christy Koji Kelly. He gave an introductory talk on the rough geometry. Reported by Keita Mikami
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2022-12-05
セミナーレポートiTHEMS Math Seminar by Dr. Yusuke Aikawa on November 18, 2022
On November 18th, Yusuke Aikawa, from Information Technology R&D Center, Mitsubishi Electric Corporation, gave a talk in Math Seminar. In the first part of the talk, he made a general introduction to the public key cryptography and its historical development. In particular, he explained that a large-scale quantum computer can break today’s public key security systems. In the second part, he explained the recent attempts to create public key systems which are not easily breakable by quantum computers (so called post-quantum cryptography), with an emphasis on the methods which use elliptic curves. An elliptic curve is an algebraic curve which admits a group structure, and one can form a cryptography by using this group structure. The speaker also explained his recent joint work on a generalized methods which uses abelian varieties, which are higher dimensional algebraic varieties admitting group structure. Reported by Hiroyasu Miyazaki
