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1084 イベント
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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
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Multimessenger probes of superheavy dark matter decay and annihilation
2024年3月26日(火) 10:18 - 11:00
Saikat Das (京都大学 基礎物理学研究所 ポスドク研究員)
We revisit constraints on decaying very heavy dark matter (VHDM) using the latest ultrahigh-energy cosmic-ray (UHECR; E >1e18 eV) data and ultrahigh-energy (UHE) gamma-ray flux upper limits, measured by the Pierre Auger Observatory. We present updated limits on the VHDM lifetime for masses up to ∼ 1e15 GeV, considering decay into quarks, leptons, and massive bosons. In particular, we consider not only the UHECR spectrum but their composition data that favors heavier nuclei. Such a combined analysis improves the limits at <1e12 GeV because VHDM decay does not produce UHECR nuclei. We also show that the constraints from the UHE gamma-ray upper limits are ∼ 10 times more stringent than that obtained from cosmic rays, for all of the Standard Model final states we consider. The latter improves our limits to VHDM lifetime by a factor of two for dark matter mass >1e12 GeV. We also provide constraints using neutrino flux from dark matter decay, including the neutrino-induced cascades. We consider the interaction of UHE neutrinos with the cosmic neutrino background, leading to the attenuation of the extragalactic flux reaching Earth, which improves our analysis to obtain tighter constraints.
会場: via Zoom
イベント公式言語: 英語
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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
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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
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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
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Do plants have bones? Silica phytoliths and their role and fate in the development of terrestrial plants and human civilizations
2024年3月1日(金) 14:00 - 15:15
Mikhail Blinnikov (Professor, St. Cloud State University, USA)
Silicon is the second most common element in the Earth’s crust. Some families of higher plants evolved mechanisms for soluble silica to be carried by xylem from groundwater and deposited as plant opal in or around plant cells as phytoliths thought to play a role in the structural support and defense against herbivores. While known since the early 19th century, phytoliths remain an intriguing class of microfossils whose formation and role in plants and their preservation in soils and sediments are a subject for a lot of active research. I outline some emerging themes in phytolith analysis including phytoliths’ role in global biogeochemical cycles, plant-herbivore interactions, and their tracing of evolution of cultural plants, especially cereals such as rice (Oryza), wild rice (Zizania), maize (Zea), wheat (Triticum) and millet (Panicum), all relevant to global archaeology. Some emerging research on phytoliths connects their changes in shapes to plant taxonomy of some families such as grasses and opens up avenues for further investigation of their active construction in the cells of some taxa by yet undiscovered genetically mediated mechanisms. New image analysis techniques and some advanced microscopy methods will allow us to further the field of phytolith study using deep machine learning algorithms and true 3D analysis of their shapes, something where contribution from other branches of science are most welcome.
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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Stochastic tunneling in de Sitter spacetime
2024年2月28日(水) 16:00 - 17:30
宮地 大河 (神戸大学 大学院理学研究科 物理学専攻 宇宙論研究室 博士課程)
The formulation of tunneling in real time formalism is discussed. In the case of de Sitter spacetime, there is a method called the stochastic approach, which is known to reproduce the tunneling predicted by Hawking and Moss in the imaginary time formalism. In the case of accelerated expansion of space, the short-wavelength modes are stretched and transformed into long-wavelength modes. In the stochastic approach, such UV-IR transition is incorporated as quantum noise, and the dynamics of the long-wavelength modes are described by stochastic differential equations. In this talk, we construct a Schwinger-Keldysh path integral that reproduces this stochastic differential equation and reformulate the tunneling probability. We also reproduce the Hawking-Moss tunneling probabilities by using the saddle point approximation.
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
Basic experimental considerations for analyzing gene expression
2024年2月28日(水) 13:00 - 14:00
藤 博貴 (理化学研究所 開拓研究本部 (CPR) 岩崎RNAシステム生化学研究室 学振特別研究員PD)
Methods such as RNA-sequencing and ribosome profiling are indispensable tools for the comprehensive elucidation of the mechanisms underlying gene expression. A fundamental aspect that requires meticulous attention in the execution of these experiment is the extraction of intact RNA and Ribosomes. The integrity and purity of the extracted RNA is critical to ensure the accuracy and reliability of the sequencing data. In this seminar, I will introduce the basic but key points of the extraction process.
会場: 研究本館 3階 共有スペース
イベント公式言語: 英語
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Using a trapped ion quantum computer for hamiltonian simulations
2024年2月28日(水) 10:30 - 12:00
リナルディ エンリコ (クオンティニュアム株式会社 Quantum Machine Learning and Algorithms Senior Research Scientist)
Trapped ion quantum computers, like the H-series quantum hardware by Quantinuum, robustly encode quantum information in long lived and precise qubits. However, utilizing the hardware efficiently requires a full-stack workflow from software libraries to hardware compilers. In this talk we introduce the relevant elements of this stack in the context of solving the quantum dynamics of a spin system on H-series hardware: we start from the definition of the Hamiltonian operator in the qubit Hilbert space using the open-source pytket python library and we define the quantum circuits in measurements to run, on a simulator first and on hardware later.
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
Plant hackers: galling insects extend their phenotypes on the trees by novel plant organogenesis
2024年2月27日(火) 16:00 - 17:00
Xin Tong (理化学研究所 環境資源科学研究センター (CSRS) 細胞機能研究チーム 基礎科学特別研究員)
When it comes to plant-insect interactions, insects are generally seen as pests like caterpillars eating vegetables or fruits. However, one group of insects, the galling insects can induce de novo organogenesis on the host plants which are often woody plants. Each galling insect species ‘designs’ its own gall as the extended phenotype which are so-called species-specific gall formation. Different from leaves and roots, galls represent unique plant organs swiftly formed in response to parasitic organisms, observed across diverse plant species. Yet, the precise mechanisms by which normal plant development is interrupted and redirected to form galls by galling organisms remain elusive. During the talk, I will share some discoveries and views related to aphid gall formation on the elm tree, which is the super host plant for more than 30 galling species, and further discussion about why an insect gall is not simple cell mass but well-organized structure, and how we could systematically understand insect gall formation.
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
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An Investment Banker’s Journey to the World of Physicists -Seeking the Truth in Economics and Finance
2024年2月26日(月) 15:30 - 17:00
Irena Vodenska (Professor, Boston University, USA)
I encountered many exciting opportunities to learn, grow intellectually, and teach during my educational, professional, and scientific journey. Life brings chances, and it is up to us to take or leave them. I took my chances, one of the fascinating ones being to embark on a scientific interdisciplinary research collaboration with physicists. My background is in economics and finance, and doing research with physicists has been fascinating from many different points of view, especially in light of being free from any ONE discipline, free to explore research possibilities to answer finance and economic questions based on a boundless horizon of possible solutions. I worked as an investment banker after my first graduate degree before returning to academia to continue chartering new pathways to research. During my work as a hedge fund manager and a NASDAQ market maker, I had an opportunity to witness firsthand, on the trading floor, the US market collapse sparked by the demise of the Long Term Capital Management in 1998 and later the European market plunge during the tragic events of the terrorist attack on New York City on September 11, 2001, when I lived and worked on Manhattan. Most world problems today are complex to solve with one discipline, as multidisciplinary THINKING is needed to cover various aspects of scientific inquiry. Experience is essential, translating real-world knowledge into academia even more so. I was fortunate to be in a position to build the bridge between investment banking and academia. Learning about the pioneer of Econophysics, Boston University Professor H. Eugene Stanley, was like discovering a gold mine for me. After an exciting investment banking experience in the 1990s and early 2000s, I left my investment banking job in New York City to join Professor Stanley’s research laboratory, a time I will cherish and remember as formative, enlightening, and transformative for the rest of my life. One may ask why physicists work with economists on financial economics problems. The answer is simple: physicists are naturally curious, inquisitive, and open to new ideas. Moreover, physicists and economists share the same language, the language of mathematics. The value of the achievement in econophysics research is the results and the empirical outcome based on data obtained with solid models grounded in natural and social science theory. It is not trivial to produce interdisciplinary research, but recognizing its necessity is already prominently featured in many universities’ strategic plans, including Boston University. Let me lay out several studies and results to give you a glimpse into the research I will discuss today. We analyze economic time series and panel data to understand their relationships and investigate whether some economic data could be informative of the behavior of others. We use a novel approach comprised of Complex Hilbert Principal Component Analysis (CHPCA), Rotational Random Shuffling (RRS), and Helmholtz-Hodge (HH) potential to unearth statistically significant co-movements and identify noteworthy economic and geopolitical events that might influence such co-movement dynamics. I will present results from four cases studied collaboratively with my international research collaborators over the last decade since 2013.
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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A Selective Survey of Ideas, Tools and Results in Constructive Field Theory
2024年2月26日(月) 13:00 - 14:30
クリスティ・コウジ・ケリー (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 this talk we discuss some aspects of constructive field theory with an emphasis on analytical and probabilistic methods and results. In particular after an overview of some points in the history of constructive QFT we plan to discuss some early achievements in axiomatic QFT, some features of the theory of distributions and the basic structure of the Wightman reconstruction theorem. We also introduce the Osterwalder-Schrader axioms and overview the strategy for the construction of nontrivial measures describing path-integrals for interacting QFTs. Depending on time constraints we might also discuss probabilistic tools (weak convergence of measures, the Bochner-Minlos theorem etc), Gaussian measures, UV regularity of simple QFTs and the construction of (infinite volume) Euclidean P(phi)_2 measures. The plan is to discuss some of these topics in some detail after the end of the official seminar.
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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Cellular-level left-right asymmetry, cell chirality, induces the chiral collective rotation of multicellular colony
2024年2月15日(木) 16:00 - 17:00
石橋 朋樹 (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 基礎科学特別研究員)
西澤 凌平 (大阪大学 大学院生命機能研究科 博士課程)The left-right (LR) asymmetric morphology of organs is essential for the development and maintenance of their functions in various species. In recent years, it has become clear that the LR asymmetry of organs originates from cell chirality, the LR asymmetric nature at the cellular level [1]. However, it is unclear how the cell chirality generates the LR asymmetry at the multicellular level. Here we show a mechanism of LR asymmetry formation at the multicellular level based on cell chirality. We previously found that Caco-2 cells, a typical cultured epithelial cell line derived from human colon cancer, exhibit stereotypical and directional cell chirality; when Caco-2 cells are cultured as single cells, their nuclei and cytoplasm rotate in the clockwise direction at a rate of 50°/h [2]. Interestingly, when Caco-2 forms multicellular colonies, the colonies also undergo a collective clockwise rotation at 10º/h. We revealed that the actomyosin cytoskeleton is essential for the formation of the collective rotation [2]. We also found that Caco-2 cells formed lamellipodia and focal adhesions LR asymmetrically during the collective colony rotation, which may be responsible for the chiral collective motion. Interestingly, the disruption of microtubules reversed the direction of collective rotation. The LR asymmetric formation of lamellipodia and focal adhesions was also reversed by inhibition of microtubule polymerization. We will discuss the possible mechanism and the mathematical model where cell chirality induces multicellular chiral rotation depending on microtubules.
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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Chemical reaction network theory and the problem of reaction rate
2024年2月8日(木) 16:00 - 17:00
須田 智晴 (理化学研究所 環境資源科学研究センター (CSRS) 生体機能触媒研究チーム 特別研究員)
A chemical system can be described at different levels. When we focus on the population of chemical species, it is convenient to consider the system as consisting of a number of chemical reactions, which assumes the structure of a (hyper)graph together with the species. The chemical reaction network theory studies chemical systems described in such a way. It aims to elucidate the dynamics of overall chemical composition in terms of the associated graph structure. Notably, it applies not only to chemical systems but also to more general systems as long as the mathematical structure is compatible. In the first part of this talk, we will review the basic concepts and results of the theory, which mainly concern the existence and stability of the equilibrium. From the viewpoint of chemical kinetics, it is interesting to consider the rate of the overall reaction, which may be obtained by the total balance of chemical species. The second part of the talk will be devoted to this topic. Formulation of the problem and some results will be presented. In particular, chemical reaction networks with first-order reactions will be considered in detail.
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
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Relativistic Jet Simulations and Modeling on Horizon Scale
2024年2月8日(木) 13:00 - 14:30
水野 陽介 (T.D. Lee Fellow / Associate Professor, Tsung-Dao Lee Institute, Shanghai Jiao Tong University, China)
Relativistic jets are launched in the vicinity of the central black holes and emit powerful radiation across the electromagnetic spectrum. According to our current understanding, relativistic jets are launched by directly tapping the rotational energy of spinning black holes via the so-called Blandford-Znajek process. In addition to the spin of the black hole, numerical simulations showed the amount of accreted magnetized flux has a major impact on the formation of relativistic jets. We have investigated the radiative signatures of self-consistently launched relativistic jets using 3D general relativistic magneto-hydrodynamical simulations and general relativistic radiative transfer calculations in horizon scale to the connection with large-scale structure. We discuss our findings and comparison with observations.
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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Recent advances in nuclear Density Functional Theory and applications to the nuclear response
2024年2月6日(火) 13:30 - 15:00
ジャンルカ・コロ (Professor, Department of Physics, University of Milan, Italy / Professor, Sezione di Milano, INFN, Italy)
In this contribution, I will give an overall (and, of course, biased) view of the general status of DFT. I will stress that, in contrast to ab initio methods, DFT is the only framework that allows the study of excited states, including those lying at relatively high energy. Accordingly, I will focus on the nuclear response. After a reminder on the nuclear Giant Resonances and the link with the nuclear equation of state, I will discuss the projection methods to restore symmetries in the calculations of deformed systems. While symmetry-restored calculations are nowadays of common use in the study of ground-state properties and low-lying excitations, similar realistic investigations for the nuclear response are essentially missing in the literature. Recently, we have implemented an exact Angular Momentum Projection (AMP) on top of Skyrme-Random Phase Approximation (RPA) calculations in a projection after variation (PAV) scheme, for the first time. The results will be critically analysed in the case of the monopole response, also taking into account the experimental investigations that can be envisioned for well-deformed systems. If time allows, the nuclear response will be also discussed as a way to improve the current density functionals and ground them on ab initio nuclear theory. This seminar is co-hosted by Nuclear Many-body Theory Laboratory and Few-body Systems in Physics Laboratory, RIKEN Nishina Center for Accelerator-Based Science.
会場: 理化学研究所 和光キャンパス RIBF棟 2階 大会議室 (メイン会場) / via Zoom
イベント公式言語: 英語
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Nuclear Energy-Density Functional Approach to Bridging Neutron-Rich Nuclei and Neutron Stars
2024年2月5日(月) 13:30 - 15:00
吉田 賢市 (大阪大学 核物理研究センター 准教授)
Understanding the properties of neutron-rich nuclei has been a central subject in low-energy nuclear physics. The great interest lies not only in the pursuit of a variety of structures and the elucidation of the mechanisms of their occurrence but also in obtaining insights into the structure of the inner crust of neutron stars. With advances in neutron-star observation techniques, the structure of neutron stars has been becoming better understood. The data accumulated from these observations unveil properties of neutron-rich matter that are otherwise inaccessible through terrestrial experiments. In this talk, I will introduce an attempt to construct a nuclear energy-density functional (EDF) inspired by the observations and then demonstrate its applicability to nuclear structure problems, including mass and deformation. One intriguing aspect of neutron stars is the emergence of superfluidity, especially the occurrence of spin-triplet pairing. I will discuss the unconventional pairing in nuclei within the nuclear EDF framework and give perspectives on the study of the phase diagram of the superfluidity in neutron stars. This seminar is co-hosted by UKAKUREN.
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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Competition across scales in biology
2024年1月31日(水) 11:00 - 12:00
シダルタ・ゴヤル (Associate Professor, Department of Physics, University of Toronto, Canada)
Many biological phenomena emerge from interaction and competition between its parts. I will share some examples across biological scales where data-driven theory can reveal new rules of biological competition. At the molecular scale competition between mitochondrial genomes within budding yeast depends on genome architecture; dynamics of adaptive immunity in microbes reveal different modalities of competition and coexistence of bacteria and its phages; in mammals cellular reprogramming may be driven by elite clones, and tumor response to drugs is driven by "epigenetic" switching. Going beyond, I will present some ideas on understanding dynamical systems that govern cell fate dynamics and if competition may play a role in it. Short bio: Sidhartha Goyal got his PhD in Physics at Princeton in 2009 and then moved to Kavli Institute for Theoretical Physics, Santa Barbara for a postdoc. He got his first degree in Electrical Engineering from IIT Bombay. He is now an Associate Professor in the Physics Department at University of Toronto interested in collective phenomena in biology across scales.
会場: via Zoom
イベント公式言語: 英語
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Quantum Enhancement in Dark Matter Detection with Quantum Computation
2024年1月22日(月) 16:00 - 18:00
Thanaporn Sichanugrist (東京大学 大学院数理科学研究科 博士課程)
陳 詩遠 (東京大学 素粒子物理国際研究センター (ICEPP) 特任助教)Title: Wave-like Dark Matter Search Using Qubits Abstract: The rapid controllability required for quantum computers makes the currently proposed quantum bit modalities also attractive as electromagnetic field sensors. One of the promising applications is wave-like dark matter searches, where the electric field converted from the coherent dark matter excites the qubits, leading to detectable signals [Phys. Rev. Lett. 131, 211001]. The quantum coherence between the qubits can be utilized to enhance the signal rate in a multi-qubit system. By designing an appropriate quantum circuit to entangle the qubits, it was found that the signal rate can scale proportionally to $n_q^2$, with $n_q$ being the number of sensor qubits, rather than linearly with $n_q$ [arXiv: 2311.10413]. In the seminar, we overview the theoretical framework of the search, elaborate on the signal-enhancing mechanism driven by quantum entanglement with specific examples of the quantum circuits, and discuss how the scheme can be implemented in the platform of future fault-tolerant quantum computers. We also provide the introduction of the experimental realization, and report the status of the experimental works carried out in UTokyo/ICEPP.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Knot Theory in Doubly Periodic Tangles and Applications
2024年1月19日(金) 15:00 - 16:30
ソニア・マムーディ (東北大学 材料科学高等研究所 (AIMR) 数学連携グループ 助教)
Doubly periodic entangled structures offer an interesting framework for modeling and investigating diverse materials and physical phenomena, from micro to large scales. Specifically, a doubly periodic tangle (DP tangle) is characterized as an embedding of an infinite number of curves in the thickened plane, derived as the lift of a link in the thickened torus to the universal cover. DP tangles play a crucial role in scientific research, particularly in fields such as materials science, molecular chemistry, and biology. Despite their widespread applications, a universally accepted mathematical description of DP tangles is currently lacking. One of the key challenges arises from the infinite possibilities in choosing a periodic cell (referred to as a motif) for a DP tangle, taking into account various periodic boundary conditions. In this presentation, we conduct a comprehensive examination of the concept of topological equivalence of DP tangles, offering insights into potential classifications and applications in the process.
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
1084 イベント