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iTHEMS Cosmology Forum 1 - Cosmic Birefringence and Parity Violation in the Universe

2024年5月14日(火) 9:30 - 18:00

並河 俊弥 (東京大学 カブリ数物連携宇宙研究機構 (Kavli IPMU) 特任助教)
白石 希典 (公立諏訪東京理科大学 共通・マネジメント教育センター 准教授)
高橋 史宜 (東北大学 大学院理学研究科物理学専攻 教授)

iTHEMS Cosmology Forum Workshop is a series of short workshops, each focused on an emerging topics in cosmology. The targeted audience is cosmologists, high-energy physicists and astronomers interested in learning about the subject, not just those who have already worked on the topic. The goal of the workshop is to provide working knowledge of the topic and leave dedicated time for discussions to encourage mutual interactions among participants. The first workshop is devoted to cosmic birefringence, a newly establishing cosmological probe of the nature of our universe. Cosmic birefringence is the rotation of the linear polarization plane of the cosmic microwave background (CMB) radiation and, thanks to its origin, inherently measures the degree of parity violation in the cosmic history. This one-day workshop gathers both the observational and theoretical aspects of this growing topic. The workshop will be in English. The venue is on RIKEN Wako Campus, and the exact room is yet to be determined, depending on the number of registered participants. The workshops are organised by the iTHEMS Cosmology Forum working group, which is the successor of the Dark Matter Working Group at RIKEN iTHEMS. Important dates: 30th April - Registration deadline 14th May - Workshop Day Invited Speakers: Toshiya Namikawa (Kavli IPMU) Maresuke Shiraishi (Suwa University of Science) Fuminobu Takahashi (Tohoku University) Organisers: Kohei Hayashi, Nagisa Hiroshima, Derek Inman, Amaury Micheli, Ryo Namba

会場: 研究本館 4階 435-437号室

イベント公式言語: 英語

Nuclear Fusion and its Interdisciplinary Fields

2024年5月14日(火) 9:00 - 18:15

We will learn about nuclear fusion and related subjects, such as turbulence in astronomy and astrophysics, from experts and discuss possible interdisciplinary collaborations in the near future. Some researchers will visit RIKEN iTHEMS from the National Institute for Fusion Science (NIFS) and other universities and research institutes for the workshop. We will have the workshop in a hybrid style so that many researchers in Japan can hear the presentations even remotely. This workshop is supported by Moonshot Goal 10 (Program Director Yoshida Zensho (NIFS)). Program Session１ 9:00-9:35 (25+10: 25 mins for Presentation, 10 mins for Q&A)：Shinya Maeyama 9:35-10:10 (25+10): Naoki Sato 10:10-10:45 (25+10): Yohei Kawazura 10:45-11:15 Coffee Break Session２ 11:15-11:50 (25+10): Takanobu Amano 11:50-12:25 (25+10): Yosuke Matsumoto 12:25-13:00 (25+10): Akira Mizuta 13:00-14:00 Lunch Break Session３ 14:00-14:35 (25+10): Chiho Nonaka 14:35-15:10 (25+10): Takeo Hoshi 15:10-15:45 (25+10): Motoki Nakata 15:45-16:15 Coffee Break Session ４ 16:15-16:50 (25+10): Kumiko Hori 16:50-17:25 (25+10): Yutaka Ohira 17:25-18:00 (25+10): Camilia Demidem (TBC) 18:30-20:30: Dinner in the Main Research Building.

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

Quantum Computing in Omics Medicine

2024年5月10日(金) 16:00 - 17:15

角田 達彦 (東京大学 大学院理学系研究科 生物科学専攻 教授)

(The speaker is also the team leader of Laboratory for Medical Science Mathematics, RIKEN Center for Integrative Medical Sciences. This is a joint seminar with the iTHEMS Biology Group.) In medical science, the recent explosive development of omics technologies has enabled the measurement not only of bulk data from entire tissues, but also data for individual cells and their spatial location information, and even allowed collection of such information in real-time. Meaningful interpretation of these rich data requires an ability to understand high-order and complex relationships that underpin biological phenomena such as drug response, simulating their dynamics, and selecting the optimal treatment for each patient based on these results. While these data are large-scale and of ultra-high dimensionality, they are also often sparse, with many missing values in the measurements and frequent higher-order interactions among variables, making them hard to handle with conventional statistics. To make further progress, machine learning – especially deep learning – is emerging as one of the promising ways forward. We have developed a method to transform omics data into an image-like representation for analysis with deep learning (DeepInsight) and have successfully used it to predict drug response and to identify original cell types from single-cell RNA-seq data. However, anticipation of the vast amount of medical data being accumulated gives particular urgency to addressing the problems of the time it actually takes to train deep learning models and the complexity of the necessary computational solutions. One possible way to resolve many of these problems is “quantum transcendence”, which is made possible by quantum superposition computation. Among all the different ways to apply quantum computation to medical science, we are particularly interested in quantum deep learning based on optimization and search problems, quantum modeling of single nucleotide detection by observational systems and statistical techniques such as regression analysis by inverse matrix computation and eigenvalue computation. In this seminar, I will first present an overview of how quantum machine learning and quantum deep learning can be used to formulate treatment strategies in medicine. We will discuss how to implement the quantum DeepInsight method, the challenges of noise in quantum computation when training QCNNs, feature mapping issues, problems of pretraining in quantum deep learning, and concerns relating to handling sensitive data such as genomic sequences. I hope this seminar will enhance our understanding of how to effectively facilitate medical research with quantum computing.

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

Surrogate Modeling for Supernova Feedback toward Star-by-Star Simulations of Milky-Way-sized Galaxies

2024年5月10日(金) 14:00 - 15:15

平島 敬也 (東京大学 大学院理学系研究科 天文学専攻 博士課程)

Galaxy simulations have found the interdependence of multiscale gas physics, such as star formation, stellar feedback, inflow/outflow, and so on, by improving the physical models and resolution. The mass resolution remains capped at around 1,000 solar masses (e.g., Applebaum et al. 2021). To overcome the limitations, we are developing a new N-body/SPH code, ASURA-FDPS, to leverage exascale computing (e.g., Fugaku), handle approximately one billion particles, and simulate individual stars and stellar feedback within the galaxy. However, the emergence of communication costs hinders scalability beyond one thousand CPU cores. One of the causes is short timescale events localized in tiny regions, such as supernova explosions. In response, we have developed a surrogate model using machine learning to duplicate supernova feedback quickly (Hirashima et al., 2023a,b). In the presentation, I report the fidelity and progress of the simulations with our new machine-learning technique.

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

Deep Learning for Estimating Two-Body Interactions in Mixed-Species Collective Motion

2024年5月9日(木) 16:00 - 17:00

上道 雅仁 (東京大学 大学院総合文化研究科 特任研究員)

(This is a joint seminar with the Information Theory Study Group.) Collective motion is a fundamental phenomenon observed in various biological systems, characterized by the coordinated movement of individual entities. Such dynamics are especially crucial in understanding cellular behaviors, which can now be observed at an individual level in complex tissue formations involving multiple types of cells, thanks to recent advancements in imaging technology. To harness this rich data and uncover the hidden mechanisms of such dynamics, we developed a deep learning framework that estimates equations of motion from observed trajectories. By integrating graph neural networks with neural differential equations, our framework effectively predicts the two-body interactions as a function of the states of the interacting entities. In this seminar, I will first introduce the structure and hyperparameters of our framework. Subsequently, I will detail two numerical experiments. The first is a simple toy model that was employed to generate data for testing our framework to refine the hyperparameters. The second explores a more complex scenario mimicking the collective motion of cellular slime molds, highlighting our model's ability to adapt to mixed-species interactions.

会場: 研究本館 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

How Stars End Their Lives

2024年4月26日(金) 14:00 - 15:15

Philipp Podsiadlowski (Professor, University of Oxford, UK)

While the basic evolution of stars has been understood for many decades, there are still major uncertainties in our overall understanding of how stars end their lives, both in the context of low- and intermediate-mass stars (including the Sun) and massive stars. I will first review some of key principles that govern the structure and evolution of stars and then present recent progress that has been made for both groups of stars. I will argue and present numerical simulations that show that all stars become dynamically unstable when they become large giant stars, which leads to sporadic, dynamical mass ejections. Low- and intermediate-mass stars may lose all of their envelopes as a consequence, leaving white-dwarf remnants. More massive stars experience core collapse, leaving a neutron-star or black-hole remnant, possibly associated with a supernova explosion. I will show how the dramatic recent progress on understanding the core-collapse process, for the first time, allows us to connect the late evolution of massive stars with the resulting supernova explosions and the final remnants and discuss how observations with current gravitational-wave detectors (such as LIGO) will allow us to test this theoretical connection.

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

Tracing link of cell ageing and disease progression: Joining factors and facilitators

2024年4月25日(木) 16:00 - 17:00

ラジクマール・シング カルラ (沖縄科学技術大学院大学 (OIST) 免疫シグナルユニット 研究員)

Cell ageing is an inevitable biological process. It marks declined homeostatic processes in a cell, the impact of which is reflected in the organism’s function/physiology. Ageing, thus, raises risks of disease progression in elderly people and compromises their immunity. Progression of cancer and neurodegenerative diseases and weak immune response against a pathogen(s) represent cases of ageing-related diseases. What molecular factors/signaling could be associated with disease progression or take part in governing such decisions in aging? – remained a key focus of my research so far. In my talk, I shall shed light on the part characterizing key proteins and their signalling in ageing-related diseases with an emphasis on cancer, neurodegenerative disease, and immunity. Taking advantage of wet lab and system biology studying gene networks, and genomic, proteomic, and metabolomic readouts, I investigated the molecular expression and processes impacted and compromised by ageing. I shall be discussing new knowledge from my work on the linkage of cell ageing and disease progression and therein role of key factors and facilitators I studied.

会場: via Zoom

イベント公式言語: 英語

A night out with ghosts

2024年4月24日(水) 16:00 - 17:30

Veronica Errasti Diez (Research Fellow, Faculty of Physics, Ludwig-Maximilians-Universität München, Germany)

Field theories are the chief theoretical framework for physics. For instance, the Standard Model and General Relativity are widely accepted as accounting for subatomic particle and gravitational behavior, respectively. Nonetheless, even such acclaimed field theories have their limitations, such as the mysterious neutrino masses and dark sector. A natural and popular way around the hurdles consists in generalizations of field theories, via the inclusion of non-linear and/or higher-order corrections. Unless painstakingly avoided, these corrections lead to the propagation of negative kinetic energy modes, or ghosts for short. Ghosts have earned an appalling fame: kill, exorcise, avoid… No efforts are spared to guarantee their absence. In this talk, we will delve into the root causes for the ill name of ghosts. As a result, we will take up the cudgels for ghosts. While they do have a strong tendency to yield ill-behaved theories, ghosts are not intrinsically pathological. As we will see, good-natured ghosts open the door to multi-disciplinary tantalizing opportunities…! And ghosts make excellent party-goers, so make sure not to miss this appointment!

会場: 研究本館 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

iTHEMS × academist オンラインイベント「数理で読み解く科学の世界 2024」

2024年4月21日(日) 10:00 - 15:30

儀保 伸吾 (理化学研究所 数理創造プログラム (iTHEMS) 特別研究員)
佐野 岳人 (理化学研究所 数理創造プログラム (iTHEMS) 基礎科学特別研究員)
辰馬 未沙子 (理化学研究所 数理創造プログラム (iTHEMS) 研究員)
内藤 智也 (理化学研究所 数理創造プログラム (iTHEMS) 基礎科学特別研究員)

「数理で読み解く科学の世界」は、2020年より毎年4月に開催しているオンラインイベントです。iTHEMS所属の若手研究者4名が最先端の研究について中学生や高校生にもわかるように30分の講演を行います。また、一般参加者からの質問やコメントを受け付ける時間も設けています。 詳細、参加お申し込みは、関連リンクをご覧ください。 日時：2024年4月21日（土）10:00〜15:30 場所：Web会議サービス「Zoom」（申込者に事前に招待URLをお伝えいたします） 参加費：無料（途中参加・退出OK） 対象者：中学生・高校生、社会人（どなたでもご参加いただけます） 主催：iTHEMS 共催（企画・運営・宣伝）：アカデミスト株式会社 タイムスケジュール： 10:00～　開始の挨拶・イベント概要説明 10:15～　講演 12:10～　昼休み企画　学習資料「一家に１枚　世界とつながる“数理”」制作秘話 13:05～　講演 15:00〜　アフタートーク 15:30　　終了予定 講演者および発表タイトル： 10:15～11:10 儀保 伸吾 博士「体の中で1日を測る時計の仕組み」 11:15～12:10 佐野 岳人 博士「エキゾチックな数学の世界」 13:05～14:00 辰馬 未沙子 博士 「惑星の作り方〜ふわふわ成長理論〜」 14:05～15:00 内藤 智也 博士「コンピュータでさぐる物質の性質と起源」

会場: via Zoom

イベント公式言語: 日本語

Zooming into the ancient world by reconstructing the joint genealogies of modern and ancient humans

2024年4月18日(木) 16:00 - 18:00

シュパイデル 玲雄 (Senior Research Fellow, Genetics Institute, University College London, UK)

In recent years, we have gone from databases that store the genetic differences observed between hundreds of thousands of sequenced people to using this information to build the actual genetic trees that relate individuals through their shared ancestors back in time. These genetic trees describe how our genomes have evolved up to millions of years into the past. Additionally, sequencing of DNA from ancient human bone has enabled the direct observation of genomic change over past millennia and has unlocked numerous previously hidden genetic histories. In this talk, I will illustrate how we can unearth the human past from these data, ranging from ancient migrations out of Africa and subsequent mixtures with now extinct Neanderthals to waves of ancestry transformations in a nation’s recent past.

会場: via Zoom

イベント公式言語: 英語

Quantum Fine-Grained Complexity

2024年4月18日(木) 10:30 - 12:00

Harry Buhrman (Chief Scientist for Algorithms and Innovation, Quantinuum, UK)

(The speaker is also a professor at University of Amsterdam & QuSoft. This is a joint seminar with the iTHEMS Quantum Computation Study Group.) One of the major challenges in computer science is to establish lower bounds on the resources, typically time, that are needed to solve computational problems, especially those encountered in practice. A promising approach to this challenge is the study of fine-grained complexity, which employs special reductions to prove time lower bounds for many diverse problems based on the conjectured hardness of key problems. For instance, the problem of computing the edit distance between two strings, which is of practical interest for determining the genetic distance between species based on their DNA, has an algorithm that takes O(n^2) time. Through a fine-grained reduction, it can be demonstrated that a faster algorithm for edit distance would imply a faster algorithm for the Boolean Satisfiability (SAT) problem. Since faster algorithms for SAT are generally considered unlikely to exist, this implies that faster algorithms for the edit distance problem are also unlikely to exist. Other problems used for such reductions include the 3SUM problem and the All Pairs Shortest Path (APSP) problem. The quantum regime presents similar challenges; almost all known lower bounds for quantum algorithms are defined in terms of query complexity, which offers limited insight for problems where the best-known algorithms take super-linear time. Employing fine-grained reductions in the quantum setting, therefore, represents a natural progression. However, directly translating classical fine-grained reductions to the quantum regime poses various challenges. In this talk, I will present recent results in which we overcome these challenges and prove quantum time lower bounds for certain problems in BQP, conditioned on the conjectured quantum hardness of, for example, SAT (and its variants), the 3SUM problem, and the APSP problem. This presentation is based on joint works with Andris Ambainis, Bruno Loff, Florian Speelman, and Subhasree Patro.

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

Short-Lived Hawking Radiation Under Stringy Effects

2024年4月11日(木) 13:30 - 15:00

ウェイシャン・シャオ (Ph.D. Student, Department of Physics, National Taiwan University, Taiwan)

A UV theory is required in order to describe the origin of late-time Hawking radiation. In this talk, I will explore Hawking radiation in a non-local model of the radiation field inspired by Witten's open string field theory. An attempt at extracting the correlators of this theory will be discussed, which leads to a space-time uncertainty relation. As a result, the characteristics of trans-Planckian field modes differ significantly from that in the standard low-energy effective theory, and I will argue that this ultimately results in the termination of Hawking radiation around the scrambling time of the black hole.

会場: 研究本館 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

A socio-ecological and genomic approach to mixed-species formation of African forest guenons

2024年4月4日(木) 16:00 - 17:00

北山 遼 (北海道大学 大学院環境科学院 博士課程)

While many animal groups consist of a single species, some species have been observed forming mixed-species groups (MSGs). It is thought that by forming groups with different species, animals may reduce predation risk, improve foraging efficiency, and even gain social and reproductive benefits. Red-tailed monkeys and blue monkeys, African forest guenons (Tribe Cercopithecini), are known to form MSGs in several regions in Africa, despite the large niche overlap. The underlying mechanisms driving the formation of MSGs in red-tailed monkeys and blue monkeys are still unclear. One reason is that previous studies have been limited to behavioral ecological approaches. By combining field observations with genomic analyses in the laboratory, we seek to shed light on the role of genetic factors in mediating interspecies interactions within MSGs. In this talk, I will introduce our studies on genomic introgression and gut microbiome sharing within the mixed-species population of red-tailed monkeys and blue monkeys in the Kalinzu Forest Reserve, Uganda.

会場: via Zoom

イベント公式言語: 英語

TadaFest 2024: Toward understanding of the Origin of Spacetime

2024年4月2日(火) 14:00 - 18:00

多田 司 (理化学研究所 数理創造プログラム (iTHEMS) 副プログラムディレクター)

Program 14:00-14:05 Welcome address T. Hatsuda (RIKEN iTHEMS) 14:05-15:35 T. Tada (RIKEN iTHEMS) "Toward understanding of the origin of spacetime" (This talk is in English) 15:35-16:00 coffee break 16:00-16:30 Shin Nakamura (Chuo Univ.) "Application of gauge/gravity duality: application to non-equilibrium physics" (This talk is in Japanese) 16:30-17:00 Kinya Oda (Tokyo Woman's Chiristian Univ.) "Gaussian formalism: From Hesenberg's Uncertainty Principle to Time-Boundary Effect and Lorentz-Covariant Complete Basis for Spinors" (This talk is in Japanese) 17:00-17:30 Gen Tatara (RIKEN, CEMS) "Some topics of spintronics" (This talk is in Japanese) 17:30-18:00 Asato Tsuchiya (Shizuoka Univ.) "Recent progress in the studies of the emergence of space-time in the type IIB matrix model" (This talk is in Japanese) 18:15- informal discussion @ Common space on 3F of the main research building

会場: 大河内記念ホール (メイン会場) / via Zoom

イベント公式言語: 英語

Arrhythmic activity rhythms in ants

2024年3月26日(火) 16:00 - 17:00

藤岡 春菜 (岡山大学 環境生命自然科学学域 助教)

Most organisms exhibit a periodic activity of about 24 h. This circadian rhythm is considered to be an adaptation to the fluctuations of the environment. In social insects such as honeybees and ants, individual behavior, including activity-rest rhythms, is influenced by interactions within the colony. However, it is challenging to monitor individual activity-rest rhythms in an ant colony due to their large group size and small body size. To address this, we developed an image-based tracking system using 2D barcodes a monomorphic ant and measured the locomotor activities of all colony members under laboratory conditions. Activity-rest rhythms appeared only in isolated ants, not under colony conditions. This suggests that a mixture of social interactions, not light and temperature, induces the loss of activity-rest rhythms. These findings contribute to our understanding of the diverse patterns of circadian activity rhythms in social insects.

会場: via Zoom

イベント公式言語: 英語

The evolution of unusual inheritance and chromosome behaviour in flies and other critters

2024年3月14日(木) 16:00 - 17:00

Laura Ross (Senior Lecturer, Institute of Evolutionary Biology, University of Edinburgh, UK)

Under Mendelian inheritance, individuals receive one set of chromosomes from each of their parents, and transmit one set of these chromosomes at random to their offspring. Yet, in thousands of animals Mendel's laws are broken and the transmission of maternal and paternal alleles becomes unequal. Why such non-Mendelian reproductive systems have evolved repeatedly across the tree of life remains unclear. My lab studies a variety of arthropod species to understand why, when and how the transmission of genes from one generation to the next deviate from Mendel’s laws. We mainly focus on species with Paternal Genome Elimination: Males transmit only those chromosomes they inherited from their mother to their offspring, while paternal chromosomes are excluded from sperm through meiotic drive. I will present recent work aimed at understanding the evolution of this unusual reproductive strategy in a clade of flies. These flies arguably have one of the most bizarre and complex chromosome systems of any insect and we use this complexity to study a range of topics including the evolution of sex chromosomes, germline-restricted chromosomes and sexual conflict.

会場: セミナー室 (359号室) / via Zoom

イベント公式言語: 英語

New horizons in immersive visualization at iTHEMS

2024年3月14日(木) 14:00 - 16:00

ジル・フェラン (Adjunct Professor, Department of Physics and Astronomy, University of Manitoba, Canada)

Visualization is an essential part of research, both to explore one’s data and to communicate one’s findings with others. Data that are 3-dimensional can be explored in a more natural way using virtual reality devices. iTHEMS recently purchased new VR headsets with advanced capabilities (Meta Quest Pro). The meeting will start with a general introduction to the current state of the VR space. Then, participants may individually experience a demonstration with the new headsets (showing research done at the ABBL on supernovae and their remnants). There will be ample time for questions and discussions. Come and discover how such tools can be used to enhance our research.

会場: 研究本館 3階 共有スペース

イベント公式言語: 英語

Brane field theory with higher-form symmetry

2024年3月12日(火) 14:00 - 15:30

川名 清晴 (Research Fellow, Korea Institute for Advanced Study (KIAS), Republic of Korea)

We propose field theory for branes with higher-form symmetry as a generalization of ordinary Landau theory. The field \psi[C_p^{}] becomes a functional of p-dimensional closed brane Cp embedded in a spacetime. As a natural generalization of ordinary field theory, we call this theory brane field theory. In order to construct an action that is invariant under higher-form transformation, we first generalize the concept of “derivative” for higher-dimensional objects. Then, we discuss various fundamental properties of the brane field based on the higher-form invariant action. It is shown that the classical solution exhibits the area law in the unbroken phase of U(1) p-form symmetry, while it indicates a constant behavior in the broken phase for the large volume limit of Cp. In the latter case, the low-energy effective theory is described by the p-form Maxwell theory. If time permits, we also discuss brane-field theories with a discrete higher-form symmetry and show that the low-energy effective theory becomes a BF-type topological field theory, resulting in topological order.

会場: 研究本館 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

Macroscopic neutrinoless double beta decay: long range quantum coherence

2024年3月6日(水) 15:30 - 17:30

ゴードン・ベイム (Professor Emeritus, University of Illinois, USA)

This talk will introduce the concept of ``macroscopic neutrinoless double beta decay" (MDBD) for Majorana neutrinos. In this process an antineutrino produced by a nucleus undergoing beta decay, $X\to Y + e^- + \bar \nu_e$, is absorbed as a neutrino by another identical $X$ nucleus via the inverse beta decay reaction, $\nu_e + X \to e^-+Y$. The distinct signature of MDBD is that the total kinetic energy of the two electrons equals twice the end-point energy of single beta decay. The amplitude for MDBD, a coherent sum over the contribution of different mass states of the intermediate neutrinos, reflects quantum coherence over macroscopic distances, and is a new macroscopic quantum effect. We discuss the similarities and differences between the MDBD and conventional neutrinoless double beta decay, as well as give estimates of the rates of MDBD and backgrounds.

会場: 研究本館 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