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RIKEN iTHEMSのアウトリーチについての研究会 2022

2022年7月29日(金) - 31日(日)

RIKEN 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。これまでの「ジャーナリスト・イン・レジデンス・プログラム」による交流の実績の上で、RIKEN iTHEMS の研究と社会の関連付けを探るとともに、今後のジャーナリストと研究者の双方向的関係の構築のための議論を行うアウトリーチについての研究会を開催しております。本年は「RIKEN iTHEMSのアウトリーチについての研究会2022 ＠神戸&ZOOM」として、7 月29 日(金)-7月31 日(日) にiTHEMS 数理クール神戸において、できるだけ対面で、ズームを併用して開催いたします。

会場: SUURI-COOL (Kobe) / via Zoom

イベント公式言語: 日本語

Test of the Cosmological principle by observing the primordial gravitational waves

2022年7月27日(水) 13:30 - 15:00

浦川 優子 (高エネルギー加速器研究機構 (KEK) 准教授)

In this talk, using the generalized deltaN formalism, which dramatically facilitates a computation of the primordial density perturbation and the primordial GWs (PGWs), we address a violation of the Cosmological principle, namely a violation of the global isotropy in the Universe. It’s turned out that measuring the PGWs provides a powerful tool to explore a violation of the global isotropy. If time permits, I will also discuss some prospects on LiteBIRD.

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

From the Black Hole Conundrum to the Structure of Quantum Gravity

2022年7月26日(火) 15:30 - 17:00

野村 泰紀 (Professor/Director, Berkeley Center for Theoretical Physics, University of California, Berkeley, USA)

Having a complete quantum theory of gravity has long been a major goal of theoretical physics. This is because a naive merger of quantum mechanics and general relativity — though it works in certain limited regimes — suffers from major theoretical problems. A particularly acute one arises when one considers the quantum mechanics of black holes: two fundamental principles of modern physics — the conservation of probability in quantum mechanics and the equivalence principle of general relativity — seem to be incompatible with each other. I will explain how recent theoretical progress begins to address this problem and portray the emerging picture of how spacetime and gravity behave at the level of full quantum gravity.

会場: 理化学研究所 和光キャンパス RIBF棟 2階 大会議室 / via Zoom

イベント公式言語: 英語

Introduction to instanton knot homology

2022年7月25日(月) 16:00 - 18:00

井森 隼人 (京都大学 大学院理学研究科 数学・数理解析専攻 博士課程)

Floer theory is an infinite-dimensional version of Morse theory and has provided powerful invariants in the study of low-dimensional topology. In the context of Yang-Mills gauge theory, some versions of Floer homology groups for knots have been developed. These knot invariants are called instanton knot homology groups and are strongly related to representations of the fundamental group of the knot complement. In this talk, the speaker introduces basic constructions of instanton knot homology groups and recent developments related to the equivariant version of instanton knot homology theory.

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

Bayesian optimization of multivariate genomic prediction models based on secondary traits for improved accuracy gains and phenotyping costs

2022年7月21日(木) 16:00 - 17:00

濱崎 甲資 (東京大学 大学院農学生命科学研究科 博士課程)

In recent years, the genomic prediction that predicts phenotypic values from marker genotype data has attracted much more attention in the area of breeding. Especially, genomic selection using prediction values based on genomic prediction models has been contributing to more efficient and rapid breeding. In genomic prediction, it is important to construct the prediction model so that its accuracy becomes higher. Thus, multivariate genomic prediction models with secondary traits, such as data from various omics technologies including high-throughput phenotyping (e.g., unmanned aerial vehicle-based remote sensing), have started to be applied to many datasets because it offers improved accuracy gains compared with genomic prediction based only on marker genotypes. Although there is a trade-off between accuracy gains and phenotyping costs of secondary traits, no attempt has been made to optimize these trade-offs. In this study, we propose a novel approach to optimize multivariate genomic prediction models with secondary traits measurable at early growth stages for improved accuracy gains and phenotyping costs. The proposed approach employs Bayesian optimization for efficient Pareto frontier estimation, representing the maximum accuracy at a given cost. The proposed approach successfully estimated the optimal secondary trait combinations across a range of costs while providing genomic predictions for only about 20% of all possible combinations. The simulation results reflecting the characteristics of each scenario of the simulated target traits showed that the obtained optimal combinations were reasonable. Analysis of real-time target trait data showed that the proposed multivariate genomic prediction model had significantly superior accuracy compared to the univariate genomic prediction model.

会場: via Zoom

イベント公式言語: 英語

Seiberg-Witten Floer homotopy

2022年7月15日(金) 14:00 - 16:30

今野 北斗 (東京大学 大学院数理科学研究科 助教)

I will survey a mathematical object called the Seiberg-Witten Floer homotopy type introduced by Manolescu. This is a machinery that extracts interesting aspects of 3- and 4-dimensional manifolds through the Seiberg-Witten equations. This framework assigns a 3-manifold to a "space" (more precisely, the stable homotopy type of a space), and this space contains rich information that is strong enough to recover the monopole Floer homology of the 3-manifold, which is known already as a strong invariant. I shall sketch how this theory is constructed along Manolescu's original work, and introduce major applications. If time permits, I will also explain recent developments of Seiberg-Witten Floer homotopy theory. If you are not familiar with the mathematical formulation of TQFT and categorification, I recommended you to watch Dr. Sano's recent talk in advance (see related links).

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

Dual stochasticity of neurons and synapses for sampling-based learning in the brain

2022年7月14日(木) 16:00 - 17:00

寺前 順之介 (京都大学 大学院情報学研究科 先端数理科学専攻 非線形物理学講座 准教授)

Neurons and synapses behave highly stochastically in the brain. However, how this stochasticity is beneficial for computation and learning in the brain remains largely unknown. In this presentation, we will see that the stochastic processes in neurons and synapses can be integrated into a unified framework to optimally sample events from the environments, resulting in an efficient learning algorithm consistent with various experimental results. In particular, the learning algorithm enables us to reproduce the recently discovered efficient power-law coding in the cortex. These results suggest that synapses and neurons work cooperatively to implement a fundamental method for stochastic computing in the brain.

会場: via Zoom

イベント公式言語: 英語

Stem cells determine complexity of hematopoiesis and immunity: A key in maintenance of homeostasis and fighting disease

2022年7月11日(月) 10:00 - 11:30

石川 文彦 (理化学研究所 生命医科学研究センター (IMS) ヒト疾患モデル研究チーム チームリーダー)

The hematopoietic system, is a complex organ in which all cells, including white blood cells (also known as leukocytes), red blood cells and platelets originate from the hematopoietic stem cells. White blood cells/leukocytes are critical effectors of immunity. At baseline, we have about 5000-10000/microL circulating white blood cells/leukocytes, composed of more than ten distinct subsets. Among them, the most abundant (50-60%) is the neutrophil, which are capable of preventing bacterial and fungal infection. Others include T lymphocytes which attack tumors and virus-infected cells and B lymphocytes that produce immunoglobulins. Each of the leukocyte subsets have different roles in protecting us from diseases. Defects in white blood cell number or function expose us to risks of infections and tumors. Maintenance of normal homeostasis of these white blood cells is governed by expression levels of approximately 20,000 genes in hematopoietic stem cells. In this presentation, first, I will discuss current understanding of a hierarchical system of stem cells generating many different kinds of leukocytes. Second, I will talk about leukemia, a cancer of white blood cells, in which critical genes are hit by mutations, resulting in a loss or gain of function of those genes in stem cells. Third, I would like to discuss with the iTHEMS scientists potential approaches by which we can collaborate to understand the normal and diseased human blood/immune systems.

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

Virus vs. Bacteria: Art of the war in the microbial world

2022年7月7日(木) 16:00 - 17:00

御手洗 菜美子 (Associate Professor, Niels Bohr Institute, University of Copenhagen, Denmark)

A virulent phage (virus that infects bacteria) infection to a host bacterial cell results in lysis of the cell, where possibly hundreds of phage particles are released after a latency time. The phage pressure is believed to be an important factor to shape the microbial communities and a driving force of their evolution, and yet we are far from having a full picture of their warfare. In this talk, I highlight a few factors that play significant roles in phage-bacteria interactions and their coexistence, such as the effect of herd immunity and the importance of the spatial structure in a few cells scale to the colony scale. *Her talk will be accessible to physicists, mathematicians, and also biologists.

会場: via Zoom

イベント公式言語: 英語

Gradient flow exact renormalization group 2

2022年7月6日(水) 13:30 - 17:00

鈴木 博 (九州大学 大学院理学研究院 教授)

Wilson’s exact renormalization group (ERG), which tells how a system changes under the scale transformation, provides a fundamental framework to define quantum field theory even beyond the perturbation theory. It has however been known that it is difficult to preserve a manifest gauge symmetry in ERG because of the usage of the momentum cutoff in ERG. Here, we propose a possible modification of ERG, the gradient flow exact renormalization (GFERG), which preserves a manifest gauge symmetry being based on a gauge-covariant diffusion equation. I explain the basic idea and properties of GFERG. If time permits, I want to present a possible application of GFERG to the consideration of the axial anomaly.

会場: via Zoom

イベント公式言語: 英語

Gradient flow exact renormalization group 1

2022年7月5日(火) 13:30 - 17:00

鈴木 博 (九州大学 大学院理学研究院 教授)

Wilson’s exact renormalization group (ERG), which tells how a system changes under the scale transformation, provides a fundamental framework to define quantum field theory even beyond the perturbation theory. It has however been known that it is difficult to preserve a manifest gauge symmetry in ERG because of the usage of the momentum cutoff in ERG. Here, we propose a possible modification of ERG, the gradient flow exact renormalization (GFERG), which preserves a manifest gauge symmetry being based on a gauge-covariant diffusion equation. I explain the basic idea and properties of GFERG. If time permits, I want to present a possible application of GFERG to the consideration of the axial anomaly.

会場: via Zoom

イベント公式言語: 英語

Long-term evolution of a supernova remnant hosting a double neutron star binary

2022年7月1日(金) 14:00 - 15:00

松岡 知紀 (京都大学 大学院理学研究科 博士課程)

Stellar mass loss is one of the crucial elements which determine the fate of progenitors of core-collapse supernovae (SNe). Since the material released from the progenitor will be distributed as circumstellar medium (CSM), it can also have an influence on the subsequent evolution of the SN or supernova remnant (SNR). Despite its importance, mass loss histories predicted by stellar evolution models have not been incorporated with modeling for SNRs. As a first step, we investigate the dynamical evolution of an ultra-stripped supernova remnant (USSNR), originated from a type of core-collapse SN explosion proposed to be a candidate formation site of a double neutron star binary. By accounting for the mass-loss history of the progenitor binary using a model developed by a previous study, we construct the large-scale structure of the CSM up to a radius ∼100 pc, and simulate the explosion and subsequent evolution of a USSN surrounded by such a CSM environment. We find that the CSM encompasses an extended region characterized by a hot plasma with a temperature ∼10^8 K located around the termination shock of the wind from the progenitor binary (∼10 pc), and the USSNR blast wave is drastically weakened while penetrating through this hot plasma. Radio continuum emission from a young USSNR is sufficiently bright to be detectable if it inhabits our galaxy but faint compared to the observed Galactic SNRs. In this seminar I will talk about the background of the connection between the models for stellar evolution and SNRs, the details of our methods, and future prospects.

会場: via Zoom

イベント公式言語: 英語

Predicting local patterns of diversity: coexistence models, networks and wildflowers

2022年6月30日(木) 10:00 - 11:30

Margie Mayfield (Professor, University of Melbourne, Australia)

The question of how species coexist in diverse natural communities has challenged ecologists for generations. Theoretical models of species coexistence have been developed, but primarily as proof of concept for specific coexistence theories. These theories and associated models focus on coexistence between species pairs and ignore the great complexity of interactions found in most natural systems. Though useful for advancing ecological theory, these models are often of limited use for understanding and predicting diversity in real natural communities. In this talk, I explore the three main assumptions made by coexistence models developed under the framework of Modern Coexistence Theory (MCT): that only direct competition is important, that demographic variation is noise, not valuable biological information, and that only the average environment matters. Using Bayesian statistical approaches with population growth models applied to field data from the annual plant communities of the York gum woodlands of SW Western Australia, I illustrate the issues with these assumptions in predicting coexistence in diverse systems. I show how these Bayesian approaches to MCT can improve on frequentist approaches and discuss the potential value of interaction networks for studying coexistence dynamics in diverse natural systems.

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

Mathematical modeling of understanding how adaptive evolution of sexual traits can affect coexistence

2022年6月23日(木) 16:00 - 17:00

森田 慶一 (総合研究大学院大学 先導科学研究科 生命共生体進化学専攻 博士課程)

One of the challenges in ecology is understanding the processes of species coexistence. Recent studies have underlined the importance of the interaction between rapid adaptation and population dynamics (i.e., eco-evolutionary feedbacks) in coexistence. Reproductive interference may reduce population growth rate due to costs of hybridization by incomplete recognition of sexual traits such as ornaments and songs in birds. Recent theoretical studies have suggested that eco-evolutionary feedbacks in sexual traits can affect coexistence. I will present mathematical modeling for investigating how reproductive interference can affect coexistence. Furthermore, I will present an analytical method, adaptive dynamics for understanding how evolution of sexual traits can affect coexistence.

会場: via Zoom

イベント公式言語: 英語

Dress code for infrared safe S-matrix in QED

2022年6月22日(水) 13:30 - 15:00

杉下 宗太郎 (名古屋大学 高等研究院 (IAR) 特任助教)

We consider the infrared (IR) aspects of the gauge invariant S-matrix in QED. I will review the problem of IR divergences in QED, and introduce the dressed state formalism to obtain IR-safe S-matrix elements. I will show a condition for dressed states to obtain IR-safe S-matrix elements, and explain that this condition can be interpreted as the memory effect and is related to asymptotic symmetry. I also explain that IR divergences are necessary to prohibit the violation of asymptotic symmetry. We also argue that the difference between dressed and undressed states can be observed, even if we are able to observe an inclusive cross-section summing over soft photons.

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

Self-organisation of a dynamic meshwork structure in the mesoderm during the development of a chick embryo and its characterisation using persistent homology

2022年6月16日(木) 16:00 - 17:00

多羅間 充輔 (理化学研究所 生命機能科学研究センター (BDR) フィジカルバイオロジー研究チーム 研究員)

Morphogenesis is a fundamental process of development. Appropriate morphogenesis of tissues is achieved by coordinated motion of individual cells. To elucidate the mechanism behind this self-organisation of cells, one needs to develop a theoretical model based on experimental observations. In our recent study, our experimental colleague found that the mesoderm cells in early chick embryo organise into a meshwork structure, which changes dynamically. To understand the mechanism behind this dynamic meshwork structure formation, we developed an agent-based mechanical model of cells that interact through a short-range attractive interaction. To compare the simulation results with the experiment, we utilized persistent homology, a method of topological data analysis that allows to systematically characterise irregular structures. In this seminar, we will talk about the mechanical mechanism behind the mesoderm structure formation during the development of the early chick embryo, and how the persistent homology analysis is applied to our biological system.

会場: via Zoom

イベント公式言語: 英語

Algebraic geometry in mixed characteristic

2022年6月10日(金) 14:00 - 16:30

吉川 翔 (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)

In algebraic geometry, we study the geometry of algebraic varieties, which are sets defined by algebraic equations. There are two types of algebraic varieties, they are varieties over characteristic zero and varieties over positive characteristic. Algebraic geometry in characteristic zero is similar to analytic geometry, so it is related to many other subjects. In this talk, I will introduce the notion of algebraic geometry in positive characteristic and relationships between positive characteristic and characteristic zero. In order to study it, we consider families consisting of varieties over characteristic zero and varieties over positive characteristic, called mixed characteristic.

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

Core-collapse Supernova Models with Heavy Axion-like Particles

2022年6月3日(金) 14:00 - 15:00

森 寛治 (福岡大学 基盤研究機関 爆発天体研究所)

Axion-like particles (ALPs) are a class of hypothetical bosons which feebly interact with ordinary matter. The hot plasma of stars and core-collapse supernovae is a possible laboratory to explore physics beyond the standard model including ALPs. Once produced in a supernova, some of the ALPs can be absorbed by the supernova matter and affect energy transfer. We recently calculated the ALP emission in core-collapse supernovae and the backreaction on supernova dynamics consistently. It is found that the stalled bounce shock can be revived if the coupling between ALPs and photons is as high as $g_{a\gamma}\sim 10^{-9}$ GeV$^{-1}$ and the ALP mass is 40-400 MeV.

会場: via Zoom

イベント公式言語: 英語

Do the mechanisms of speciation vary with latitude? Empirical case study 1: evolution of the plant cycad genus Ceratozamia from Mexico

2022年6月2日(木) 16:00 - 17:00

ホセ サイード・グティエレス オルテガ (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)

“Species” form biodiversity, and “speciation” is the evolutionary process that originate them. Speciation can occur by stochastic processes —neutral theory— or through the influence of ecological factors —selection theory—. They are not competing theories, but rather explain different facets of speciation. But the mechanisms of speciation seem quite to depend on the group of study and its underlying spatial and temporal factors. Why do in some groups species are more prone to evolve via selection or stochastically than others? It does not exist a unified theory that can explain and predict events of speciation at the global level. However, I hypothesize that there is a latitude-association between two main mechanisms of speciation: 1) “allopatric speciation by means of niche conservatism” and 2) “ecological speciation by means of niche divergence”. The first is hypothetically more common at low latitudes, and the second is more common at high latitudes. In this context, I will use the recent results of my own empirical research on the plant cycad genus Ceratozamia from Mexico as an example to show how mechanisms of speciation seem to covariate with latitude. Hopefully, you can help me to formulate a theory that can explain where and under what factors speciation can occur.

会場: via Zoom

イベント公式言語: 英語