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936 イベント
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セミナー
Period variability can provide valuable information in oscillatory systems
2021年6月24日(木) 10:00 - 11:00
森 史 (九州大学 大学院芸術工学研究院 デザイン人間科学部門 助教)
Biological clocks generate temporally precise oscillations although they are subjected to various types of noise. In other words, oscillations with only a small variability in the period are observed under action of noise. In this talk, I focus on period variability in coupled phase oscillators and complex oscillatory dynamical systems, and present the following topics:(i) A phase oscillator subjected to noise can become to generate more precise oscillations not only when it is synchronized with periodic signal but also when it is mutually synchronized with another phase oscillator with stronger noise. (ii) In complex oscillatory dynamical systems, period variability is sensitive to the choice of an output variable and output checkpoint; it can be reduced by an appropriate selection of them. (iii) Noise intensity and coupling strength in synchronized phase oscillators can be inferred from data about period variability. This talk is based on joint researches with Dr. Hiroshi Kori (Tokyo Univ) and Dr. Alexander Mikhailov (Kanazawa Univ). *Please refer to the email to get access to the Zoom meeting room.
会場: via Zoom
イベント公式言語: 英語
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Introduction to the replica method
2021年6月23日(水) 13:30 - 15:40
樺島 祥介 (東京大学 大学院理学系研究科 教授)
The replica method is a mathematical technique for evaluating the "quenched" average of logarithm (or a real number power) of the partition function with respect to predetermined random variables that condition the objective system. The technique has a long history, dating back at least to a book by Hardy et al in 1930s, but has become well known only since its application to the physics of spin glasses in 1970s. More recently, its application range is spreading rapidly to various fields in information science, including information theory, communication theory, signal processing, computational complexity theory, machine learning, etc. In this talk, we introduce the basic idea of the replica method and its mathematical fault illustrating a few examples. *Detailed information about the seminar refer to the email.
会場: via Zoom
イベント公式言語: 英語
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Black Hole Information Paradox and Wormholes
2021年6月21日(月) 13:00 - 14:30
後藤 郁夏人 (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)
In this talk, I will explain about the recent progress in the black hole information paradox that I am involved with. The information paradox arises when a black hole evaporates by emitting Hawking radiation due to the quantum effects. Time dependence of the entropy of Hawking radiation is diagnosis of information loss caused by the black hole evaporation. If information is not lost, the entropy of Hawking radiation should obey the so-called Page curve. In recent research developments, it was found that “the quantum extremal islands” reproduce the unitary Page curve in an evaporating black hole. I will argue about how the quantum extremal islands are derived from the computation of the entropy of Hawking radiation using the gravitational path-integral.
会場: via Zoom
イベント公式言語: 英語
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Stable eigenvalues of compact anti-de Sitter 3-manifolds
2021年6月18日(金) 16:00 - 18:10
甘中 一輝 (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)
Geometric objects that have been investigated in detail so far, such as closed Riemann surfaces, are sometimes locally homogeneous. Loosely speaking, their infinitesimal behavior is the same at each point. In this talk, I would like to explain the idea of investigating such objects using the Lie group theory.In the first part of the talk, I will recall the notions of Lie group actions and their quotient spaces with examples, and then explain the definitions of locally homogeneous spaces and their deformations (Teichmüller spaces). In the second part of the talk, I will consider anti-de Sitter manifolds as a special case, i.e., Lorentzian manifolds of negative constant curvature. As in the Riemannian case, a differential operator called the Laplacian (or the Klein-Gordon operator) is defined on Lorentzian manifolds. Unlike the Riemannian case, it is no longer an elliptic differential operator but a hyperbolic differential operator. In its spectral analysis, new phenomena different from those in the Riemannian case have been discovered in recent years, following pioneering works by Toshiyuki Kobayashi and Fanny Kassel. I would like to explain stable eigenvalues of the hyperbolic Laplacian of anti-de Sitter 3-manifolds with recent progress.
会場: via Zoom
イベント公式言語: 英語
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The origin and dispersal of buckwheat
2021年6月10日(木) 10:00 - 11:00
ジェフリ・フォーセット (理化学研究所 数理創造プログラム (iTHEMS) 上級研究員)
Buckwheat, which soba noodles is made from, originated from a wild species that is distributed in southwest China, around Yunnan, Sichuan, and Tibet. We are trying to understand when, where, and how it originated and then spread across the world and came to Japan. To do so, we are using genomic data of wild samples from China and cultivated samples from various parts of the world. I will give a brief introduction about buckwheat, explain what we already know about its origin and dispersal, and show a bit of our results. I will also explain the significance of studying "domestication", that is, the process that plants/animals that humans currently use originated from their ancestral wild species. *Please refer to the email to get access to the Zoom meeting room.
会場: via Zoom
イベント公式言語: 英語
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iTHEMS-phys Intro Meeting on June 7, 2021
2021年6月7日(月) 13:00 - 14:30
内藤 智也 (東京大学 大学院理学系研究科 物理学専攻 博士課程)
横田 猛 (東京大学 物性研究所 特別研究員)
辻 直美 (理化学研究所 数理創造プログラム (iTHEMS) 特別研究員)13:00-13:20 [JST] Tomoya Naito 13:20-13:40 [JST] Takeru Yokota 13:40-14:00 [JST] Naomi Tsuji 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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An overview of genome-wide epistasis and co-selection analysis
2021年6月3日(木) 10:00 - 11:00
許 インイン (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)
This talk is a summary of research that have done by me and my team during 2016~2019. I was a postdoc researcher in Aalto university/Helsinki university in Finland. In the team, a worldwide active collaboration has happened between many fields including statistical physics, biology, computer science and statistics. The target is to analyze ultra-high dimensional large population genomic datasets of two major human pathogens, Streptococcus pneumoniae and Neisseria meningitidis, without phenotypic data. Interacting networks of resistance, virulence and core machinery genes are identified. Many different approaches have been invented and they can be generally applied to other datasets with similar mathematical setting. I will explain methods based on statistical model [1,2], mutual information [3], and theoretical performance analysis for statistical model [4]. In the end, I will briefly introduce a new phenomenon of random matrix which is discovered during the research process for statistical significance filtering [5]. *Please refer to the email to get access to the Zoom meeting room.
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on June 1, 2021
2021年6月1日(火) 13:00 - 15:00
菊地 健吾 (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)
リナルディ エンリコ (Research Fellow, Physics Department, University of Michigan, USA)
横田 宏 (理化学研究所 数理創造プログラム (iTHEMS) 特別研究員)13:00-13:20 [JST] Kengo Kikuchi 13:20-13:40 [JST] Enrico Rinaldi 13:40-14:00 [JST] Hiroshi Yokota 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 31, 2021
2021年5月31日(月) 13:00 - 15:00
難波 亮 (理化学研究所 数理創造プログラム (iTHEMS) 上級研究員)
大下 翔誉 (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)
横倉 祐貴 (理化学研究所 数理創造プログラム (iTHEMS) 上級研究員)
長瀧 重博 (理化学研究所 開拓研究本部 (CPR) 長瀧天体ビッグバン研究室 主任研究員)13:00-13:20 [JST] Ryo Namba 13:20-13:40 [JST] Naritaka Oshita (10 mins break) 13:50-14:10 [JST] Yuki Yokokura 14:10-14:30 [JST] Shigehiro Nagataki 14:30- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
Magnetorotational Instability: Current Understanding and Perspective
2021年5月28日(金) 16:00 - 17:00
簑島 敬 (海洋研究開発機構 (JAMSTEC) 副主任研究員)
The differentially rotating flow can be destabilized in the presence of a weak magnetic field through the magnetorotational instability (MRI). The MRI is considered as a possible mechanism for outward angular momentum transport and subsequent mass accretion in accretion disks. Numerous studies have been devoted to understand its nature and judge whether it can supply the power sufficient for observed transport efficiency. For example, the MHD simulation studies have attempted to reveal the scaling of the MRI on numerical (e.g., resolution and domain size) as well as physical parameters (e.g., magnetic field intensity and configuration). In this talk, I would like to discuss current understanding and perspective of the MRI through theoretical and numerical studies. I will especially focus on the impact of transport coefficients (viscosity, resistivity, and their ratio) on the evolution of the MRI and disk.
会場: via Zoom
イベント公式言語: 英語
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A Mathematical Model for Stem Cell Competition to Maintain a Cell Pool Injured by Radiation Exposure
2021年5月27日(木) 10:00 - 11:00
内之宮 光紀 (電力中央研究所)
Cancer risk of low-dose-rate ionizing radiation exposure is one of the most important issues in radiation protection. Tissue stem cells have been considered one of the targets of radiation-induced carcinogenesis. There has been a hypothesis that the carcinogenic effects of radiation can be reduced if damaged stem cells are eliminated via stem cell competition between damaged and intact stem cells. This would be particularly effective under very low-dose-rate conditions, where only a few stem cells in a stem cell pool are affected by radiation. In this presentation, I will introduce a simple mathematical model to discuss the influence of stem cell competition on the accumulation of radiation damage and show that the character of damaged cells and the size of the stem cell pool may affect the accumulation of radiation damage. *Please refer to the email to get access to the Zoom meeting room.
会場: via Zoom
イベント公式言語: 英語
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Theory of Anomalous Floquet Higher-Order Topology
2021年5月26日(水) 22:00 - 23:15
Rui-Xing Zhang (University of Maryland, College Park, USA)
Periodically-driven or Floquet systems can realize anomalous topological phenomena that do not exist in any equilibrium states of matter, whose classification and characterization require new theoretical ideas that are beyond the well-established paradigm of static topological phases. In this work, we provide a general framework to understand anomalous Floquet higher-order topological insulators (AFHOTIs), the classification of which has remained a challenging open question. In two dimensions (2D), such AFHOTIs are defined by their robust, symmetry-protected corner modes pinned at special quasienergies, even though all their Floquet bands feature trivial band topology. The corner-mode physics of an AFHOTI is found to be generically indicated by 3D Dirac/Weyl-like topological singularities living in the phase spectrum of the bulk time-evolution operator. Physically, such a phase-band singularity is essentially a "footprint" of the topological quantum criticality, which separates an AFHOTI from a trivial phase adiabatically connected to a static limit. Strikingly, these singularities feature unconventional dispersion relations that cannot be achieved on any static lattice in 3D, which, nevertheless, resemble the surface physics of 4D topological crystalline insulators. We establish the above higher-order bulk-boundary correspondence through a dimensional reduction technique, which also allows for a systematic classification of 2D AFHOTIs protected by point group symmetries. We demonstrate applications of our theory to two concrete, experimentally feasible models of AFHOTIs protected by C2 and D4 symmetries, respectively. Our work paves the way for a unified theory for classifying and characterizing Floquet topological matters. *Detailed information about the seminar refer to the email.
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 25, 2021
2021年5月25日(火) 13:00 - 15:00
杉浦 拓也 (理化学研究所 数理創造プログラム (iTHEMS) 特別研究員)
土井 琢身 (理化学研究所 仁科加速器科学研究センター (RNC) 量子ハドロン物理学研究室 専任研究員)
筒井 翔一朗 (理化学研究所 仁科加速器科学研究センター (RNC) 量子ハドロン物理学研究室 基礎科学特別研究員)
後藤 郁夏人 (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)13:00-13:20 [JST] Takuya Sugiura 13:20-13:40 [JST] Takumi Doi (10 mins break) 13:50-14:10 [JST] Schoichiro Tsutsui 14:10-14:30 [JST] Kanato Goto 14:30- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
Loewner's theorem for maps on operator domains / The structure of maps on the space of all quantum pure states that preserve a fixed quantum angle
2021年5月24日(月) 16:00 - 18:10
森 迪也 (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)
This talk is divided into two independent topics. In the first part of my talk we consider the order structure of hermitian matrices. Given two matrix domains (open connected sets of n-by-n hermitian matrices), what is the general form of order isomorphisms between them? I will explain that there is a complete correspondence between the class of order isomorphisms and that of biholomorphic mappings. In the second part we consider the metric structure of the space P(H) of all quantum pure states (= the projective space of a complex Hilbert space H). Wigner's theorem asserts that every surjective isometry of P(H) onto itself is implemented by a unitary or an antiunitary operator. Uhlhorn generalized Wigner's theorem by showing that every bijective transformation of P(H) that preserves orthogonality is implemented by a unitary or an antiunitary operator. We consider some variants of Uhlhorn's result. The first part is joint work with P. Semrl (Univ. of Ljubljana), and the second part with G.P. Geher (Univ. of Reading). Only basic linear algebra is assumed in both parts.
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 24, 2021
2021年5月24日(月) 13:00 - 14:30
田屋 英俊 (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)
関野 裕太 (理化学研究所 数理創造プログラム (iTHEMS) 訪問研究員)
邱 靖凱 (理化学研究所 数理創造プログラム (iTHEMS) 上級研究員)13:00-13:20 [JST] Hidetoshi Taya 13:20-13:40 [JST] Yuta Sekino 13:40-14:00 [JST] Ching-Kai Chiu 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
Organ-to-organ two-way coupling contributes to the stabilization of circadian clock in Arabidopsis.
2021年5月20日(木) 10:00 - 11:00
上本 恭平 (京都大学 / 奈良先端科学技術大学院大学)
Circadian clocks increase plant fitness by anticipating periodic environmental changes using unstable temporal information perceived in each tissue/organ. However, little is known about how such local and noisy temporal information regulates global and coordinated plant growth. Here, we show that nutrient-mediated two-way communication between shoots and roots stabilizes circadian rhythms and aids plant growth. The photosynthetic product, sucrose, is transported from the shoot to the root, where it regulates the expression of a clock gene and nutrients uptake rhythms. A lack of nutrient rhythms destabilizes the shoot circadian rhythms and reduces the growth rate. Our mathematical model supports that two-way communication between organs reduces the heterogeneity of the circadian rhythm, thereby maintaining the robustness of the circadian clock in a noisy environment. As with feedback loops in other hierarchies, nutrient-mediated shoot-root interorgan communication of the circadian clock is advantageous for proper growth under fluctuating environmental conditions. *Please refer to the email to get access to the Zoom meeting room.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Journal Club: Intrinsically Disordered Region (IDR)
2021年5月19日(水) 13:00 - 14:00
足立 景亮 (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 / 理化学研究所 生命機能科学研究センター (BDR) 生体非平衡物理学理研白眉研究チーム 基礎科学特別研究員)
A class of protein domain, which is called intrinsically disordered region (IDR), is known to take no rigid three dimensional structure. Recent studies have shown that IDRs can show biological functions through phase separation, and it is important to clarify what kind of amino acid sequence of IDR leads to phase separation and what kind of mutation results in malfunction. In this journal club, I will discuss these topics by reviewing recent papers. *Detailed information about the seminar refer to the email.
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 18, 2021
2021年5月18日(火) 13:00 - 14:30
本郷 優 (Postdoctoral Research Associate, Physics Department, The University of Illinois at Chicago (UIC), USA)
伊藤 悦子 (理化学研究所 仁科加速器科学研究センター (RNC) ストレンジネス核物理研究室 協力研究員)
松本 信行 (理化学研究所 仁科加速器科学研究センター (RNC) 理研BNL研究センター 計算物理研究グループ 基礎科学特別研究員)13:00-13:20 [JST] Masaru Hongo 13:20-13:40 [JST] Etsuko Itou 13:40-14:00 [JST] Nobuyuki Matsumoto 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
iTHEMS-phys Intro Meeting on May 17, 2021
2021年5月17日(月) 13:00 - 14:30
初田 哲男 (理化学研究所 数理創造プログラム (iTHEMS) プログラムディレクター)
原田 了 (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)
多田 司 (理化学研究所 仁科加速器科学研究センター (RNC) 量子ハドロン物理学研究室 副主任研究員)13:00-13:20 [JST] Tetsuo Hatsuda 13:20-13:40 [JST] Akira Harada 13:40-14:00 [JST] Tsukasa Tada 14:00- Free discussion
会場: via Zoom
イベント公式言語: 英語
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セミナー
Geometry of canonical metrics on Kähler manifolds
2021年5月14日(金) 16:00 - 18:10
井上 瑛二 (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)
The aim of this talk is to report recent trends in Kähler geometry. Kähler geometry consists of two aspects: the one is algebraic geometry and the other is metric geometry.The first one hour is an introduction for non-mathematicians. I begin with a simple example of algebraic variety from ancient Greek, which I believe is the simplest example illustrating motivation for compact complex manifolds. On the other hand, I explain the first motivation for canonical metrics in Kähler geometry via Riemann’s uniformization theorem.The last one hour is an introduction to recent trends in Kähler geometry, especially Kähler-Einstein metrics. The existence of Kähler-Einstein metrics turns out to be related to geometry of degenerations of space, which is so called Yau-Tian-Donaldson conjecture. I explain various aspects of this topic. We encounter deep studies in metric geometry, birational geometry and non-archimedean geometry. I finally explain recent breakthrough on Kähler-Ricci flow.The goal of this talk is the starting point of my study. I briefly explain my study if time permits.
会場: via Zoom
イベント公式言語: 英語
936 イベント