Early Formation of Dark Matter Halos

2023年11月24日(金) 14:00 - 15:15

デリック・ビーティー・インマン (理化学研究所 数理創造プログラム (iTHEMS) 研究員)

Cosmological observations have led to an extremely precise understanding of the large-scale structure of the Universe. A common assumption is to extrapolate large-scale properties to smaller scales; however, whether this is correct or not is unknown and many well-motivated early Universe scenarios predict substantially different structure formation histories. In this seminar I will discuss two scenarios where nonlinear structures form much earlier than is typically assumed. In the first case, the initial fluctuations are enhanced on small scales leading to either primordial black holes clusters or WIMP minihalos right after matter-radiation equality. In the second, I will show that an additional attractive dark force leads to structure formation even in the radiation dominated Universe. I will furthermore discuss possible observations of such early structure formation including changes to the cosmic microwave background, dark matter annihilation, and when the first galaxies form.

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

Volume complexity of de Sitter bubbles

2023年11月22日(水) 16:00 - 17:30

Nicolò Zenoni (大阪大学 大学院理学研究科 特任研究員)

Holographic complexity is conjectured to probe the evolution of spacetime. For black holes in anti-de Sitter (AdS) spacetime the growth rate of complexity approaches a constant value at late times, while in de Sitter (dS) spacetime it diverges at a finite critical time. In this talk, we consider geometries interpolating between AdS and dS. In particular, we discuss the evolution of volume complexity in a class of three-dimensional asymptotically anti-de Sitter geometries including dynamical bubbles of de Sitter in their interior. According to the dynamics of the bubble, complexity qualitatively behaves either as in the AdS black hole or as in the dS case. We conclude with some remarks about the possible dual interpretation.

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

X's Fast and Slow

2023年11月21日(火) 16:00 - 17:00

トーマス・ヒッチコック (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)

Sex chromosomes have long been suggested to undergo distinct evolutionary dynamics to the rest of the genome. Their distinct ploidy and transmission genetics may result in differing strengths of selection, magnitude of drift, and mutation rates to the autosomes, particularly if there are sex differences. Consequently, a body of theory and empirical work has developed investigating such differences, and how they might manifest in the rates of change between populations, and the diversity observed within populations. I will briefly review the theoretical basis of these comparisons, how we can infer rates of evolutionary change from genetic data, and what we can learn from non-model systems, particularly focusing on fungus gnats and pea aphids.

会場: via Zoom

イベント公式言語: 英語

Bridging physics and society: A case study of collective memory dynamics by socio-econophysics approach

2023年11月20日(月) 15:00 - 16:30

佐野 幸恵 (筑波大学 システム情報系 准教授)

The movements of individuals with free will are unpredictable, complex, and, needless to say, fundamentally distinct from the movements of matter. Furthermore, studying society, which forms collectives while engaging in intricate individual interactions, using mathematical models seems incredibly daunting. However, when analyzing empirical data, relatively simple mathematics often emerge in the distribution and dynamics of society at the level of collective behavior. Additionally, such mathematics often share commonalities with physical phenomena. With this background, research is progressing by applying ideas from physics to social-economic phenomena, a field known as socio-econophysics. In this presentation, I will introduce a mathematical model that addresses the decay of collective memory using access logs on the web as an example of research in socio-econophysics.

会場: 大河内記念ホール / via Zoom

イベント公式言語: 英語

第24回 MACSコロキウム

2023年11月20日(月) 14:45 - 18:00

堀毛 悟史 (京都大学 大学院理学研究科 化学専攻 教授)
森下 喜弘 (理化学研究所 生命機能科学研究センター (BDR) 発生幾何研究チーム チームリーダー)

14:45-15:00 ティータイムディスカッション 15:00-16:00 堀毛 悟史 博士（京都大学大学院理学研究科化学専攻 教授） 「金属と分子が織りなすガラスの新物質科学」 三大材料と言われるセラミックス、金属、有機高分子はいずれもガラス相を形成し、我々の生活や産業を支えています。結晶と異なりガラスはランダムな分子構造を持つため、物質設計や物性の理解は未だ大きな課題です。本講演では、金属と分子を組み合わせて作る新しいガラスの研究について紹介します。どうやってガラスの構造を設計し、合成するのか、また金属と分子が作るユニークなガラスの分子構造と機能を解説します。 16:15-17:15 森下 喜弘 博士（理化学研究所生命機能科学研究センター チームリーダー） 「位置情報の最適コーディングデザインと器官形態形成動態の原型を捉えるための時空座標系」 器官発生過程における法則を知りたい。できればそれを数学的に表現できたら嬉しいし、その法則が種間や器官間で共通であれば面白い。というような気持ちで、実験と理論の境界あたりで発生生物学の研究をしている。このセミナーでは、発生組織の中の空間情報の表現・コーディング問題に関する研究と、（大きさや発生速度が異なる）相同器官の形態形成ダイナミクスを種間で直接かつ定量的に比較するための時空座標系の提案、および生物データに適用することで種に依存しないダイナミクス（原型らしきもの）の存在を示唆する結果について紹介する。 17:15-18:00 継続討論会

会場: 京都大学 北部総合教育研究棟 1階 益川ホール

イベント公式言語: 日本語

6th QGG Intensive Lectures: Introduction to thermalization in isolated quantum systems

2023年11月20日(月) - 21日(火)

濱崎 立資 (理化学研究所 開拓研究本部 (CPR) 濱崎非平衡量子統計力学理研白眉研究チーム 理研白眉研究チームリーダー)

This is the sixth event by the Quantum Gravity Gatherings (QGG) Study Group at RIKEN iTHEMS. For this event we have invited Professor Ryusuke Hamazaki from RIKEN, to deliver pedagogical lectures on the thermalization in isolated quantum systems. This topic describes how a non-equilibrium quantum state relaxes to thermal equilibrium through a unitary time evolution. This theme has applications not only in statistical physics but also in many areas of physics. In particular, in the context of quantum gravity, understanding thermalization via a unitary time evolution is anticipated to be a key to resolving the information loss problem of black holes. In addition, the notion of typicality and thermalization is important in the AdS/CFT correspondence to understand black hole physics. We expect this event to provide insights to researchers in related fields. Ryusuke Hamazaki is a leading expert in this subject. It is our enormous pleasure to have the opportunity to learn from him the idea of thermalization and its applications related to realistic systems. This intensive lecture series is designed to be an interactive event. The intensive talk will be given in a face-to-face blackboard style (in English, no online streaming) to encourage informal and lively Q&A discussions. The program will also include short talk sessions, where participants can present a 5-minute talk on a topic of their choice, which could be about their own research, reviews of specific works, or future study interests.

会場: 研究本館 435-437号室

イベント公式言語: 英語

Introduction and prospects of topological recursion

2023年11月17日(金) 15:00 - 17:00

大須賀 けん斗 (東京大学 大学院数理科学研究科 日本学術振興会 特別研究員 PD)

Topological recursion is a universal recursive formalism that connects many branches in mathematical physics, such as enumerative geometry, algebraic geometry, integrable hierarchy, matrix models, 2d gravity, and more. In the first half of this talk, I will give a pedagogical overview of topological recursion and present simple examples from which we learn how topological recursion works. Then in the second half, I will present some ongoing research projects as well as a few future directions in topological recursion.

会場: セミナー室 (359号室)

イベント公式言語: 英語

Geometry of special nilpotent orbits

2023年11月15日(水) 14:00 - 15:30

Baohua Fu (Professor, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, China)

Special nilpotent orbits play a key role in representation theory, but their geometry is little understood. I'll first report a joint work with Yongbin Ruan and Yaoxiong Wen proposing a mirror symmetry conjecture for special nilpotent orbits and then a joint work with Daniel Juteau, Paul Levy and Eric Sommers on the proof of sliced version of Lusztig's conjecture on special pieces.

会場: via Zoom

イベント公式言語: 英語

2023年度 武蔵野大学 数理工学シンポジウム MCME SYMPOSIUM 2023

2023年11月15日(水) - 16日(木)

足立 景亮 (理化学研究所 数理創造プログラム (iTHEMS) 研究員)
國府 寛司 (京都大学 理事)
本郷 優 (新潟大学 理学部 物理学プログラム 助教)

武蔵野大学数理工学センターでは、今年も「武蔵野大学数理工学シンポジウム」を開催いたします。なお、本シンポジウムは参加費無料で、どなたでもご参加いただけます。 iTHEMSの関係者も講演予定です。以下、プログラムより一部抜粋します。 11月15日（水）11：20 - 12：30「群れの物理学：動くものがたくさん集まると何が起こる？」 足立 景亮（理化学研究所 数理創造プログラム、生命機能科学研究センター） 11月15日（水）16：20 - 17：30「力学系のリザバー計算」國府 寛司（京都大学 理学研究科・理学部、理化学研究所 数理創造プログラム） 11月16日（木）10：00 - 11：10「極限状態の量子多体問題：クォーク・ハドロンから原子核まで」本郷 優（新潟大学 理学部、理化学研究所 数理創造プログラム） 参加登録は11月14日まで。下記、関連リンクよりお申し込みください。 主催：武蔵野大学数理工学センター（MCME） 共催：理化学研究所数理創造プログラム（iTHEMS）

会場: 武蔵野大学有明キャンパス5号館301教室とZoomのハイブリッド開催

iTHEMS Graph-theory workshop: from basics to applications

2023年11月13日(月) - 14日(火)

早水 桃子 (早稲田大学 理工学術院 基幹理工学部 講師 (専任) / 国立研究開発法人科学技術振興機構 (JST) さきがけ研究者)
根上 生也 (横浜国立大学 名誉教授)
岡田 崇 (京都大学 医生物学研究所 特定准教授)
相馬 輔 (統計数理研究所 数理・推論研究系 准教授 / 総合研究大学院大学 統計科学コース 准教授)
東 俊一 (京都大学 大学院情報学研究科 教授)

We will hold a two-day workshop on graph theory, which covers a variety of topics including basic concepts and theorems in graph-theory; graph-embedding; phylogenetic tree construction; chemical reaction networks; and cactus network theory. The details are found in the website linked below.

会場: 研究本館 435-437号室

イベント公式言語: 英語

Vortex Reconnection in Classical and Quantum Fluids

2023年11月10日(金) 15:00 - 16:30

木村 芳文 (名古屋大学 大学院多元数理科学研究科 特任教授)

As a fundamental process in turbulence, vortex reconnection has been studied widely not only in classical fluids but also in quantum fluids. For the latter, the first real observation of vortex reconnection was rather recent, and since then active analyses have been continued. On the other hand, vortex reconnection in the former has a long history, and it is now studied intensively as a candidate for a solution to the problem of the regularity/Singularity of the Navier-Stokes equations, which is one of the seven millennium prize problems of the Clay Mathematical Institute. In this talk, after introducing the problem, we will present some results of analysis and simulations of the dynamical system which has been proposed to describe a vortex reconnection of two vortex rings located symmetrically on two tilted planes [1], [2], [3]. Then it will be shown that this dynamical system can be written in noncanonical Hamiltonian form with Hamiltonian, H, and a Casimir invariant, C in the limit of zero viscosity [4].

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

Patterns of fern community assembly throughout the American continent: Do the mechanisms of species diversification also vary with latitude?

2023年11月7日(火) 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)

The global latitudinal gradient of biodiversity, a pattern suggesting that the low-latitude (tropical) areas have more species than the high-latitude (temperate) areas, represents the most conspicuous pattern of correlation between the environmental/geographic variation and biodiversity distribution. Yet, the relative roles of all ecological, geographic, and historical variables that can explain the gradient are unclear. Specifically, it is because we do not have a clear link between latitude and the underlying mechanisms that originate and extinct species throughout the gradient. In other words, we lack a connection between the “macroevolutionary patterns" and “microevolutionary processes”. I am researching the community assembly of ferns from the American continent, as it seems to be a group that can give some answers to what causes the latitudinal gradient of biodiversity and how the gradient is related to the processes of speciation and extinction. Regarding the community assembly, as expected, I found that the fern community clearly follows the latitudinal gradient: the number of species and localities colonized by ferns decrease with latitude. Also, this pattern is associated to a strong phylogenetic structure: the community at each latitudinal area is dependent of the previously colonizing genera (in other words, genera tend to diversify within specific latitudinal spans; most of them are restricted to the tropics). These results suggest that the fern community from the American continent follows the latitudinal gradient, and that it is a good representer of this pattern. Then, using linear regressions, I tested some classical hypotheses that have been proposed to explain the latitudinal gradient (e.g., that tropical environments, being more thermodynamically active, promote higher speciation rates). However, my results so far, suggest that none of the previously proposed hypotheses give a satisfactory explanation: there is no a single factor that can link the gradient with the processes of speciation or extinction. Rather, my data suggest that to promote speciation, the relative roles of environmental differentiation, geographic isolation, niche divergence, and time since divergence between sister species pairs vary with latitude. For example, to become new species, species near the equator did not need much geographic isolation or niche divergence from their sister counterparts (i.e., near the equator, species pairs tend to be more sympatric and present higher niche overlap). I hope my talk can stimulate some discussion about how to approach and treat the data that I have compiled, and that we can create opportunities for further collaboration.

会場: via Zoom

イベント公式言語: 英語

Compact Star Solutions Beyond General Relativity

2023年11月7日(火) 13:30 - 15:00

沼尻 光太 (名古屋大学 大学院理学研究科 博士課程)

The neutron star solutions have been gathering attention. Their high compactness enables us to observationally access the information about extreme regimes of hadron physics. On the other hand, their strong gravity features bring up another possibility, gravity beyond general relativity (GR). Although GR has been a great success until now, the present scenario for our universe still has several problems, such as dark sectors and the quantum description of gravity. To tackle these problems, the modified gravity theories have been discussed for decades. Their modifications are expected to become noticeable in strong gravity regimes like compact stars. In this talk, I will discuss the configuration of the compact star solution under the F(R) gravity, one of the most popular and simplest modifications of GR. The background hydrostatic solutions are calculated with some F(R) models, which show non-trivial influences from the additional scalar DOF in this theory. The tidal deformation phenomenon is also considered to focus on another observable, tidal deformability. I will comment on how to utilize obtained observables to determine the gravity theory and the unknown equation of state simultaneously.

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

Mathematical modelling of the host response to inhalational anthrax across different scales

2023年10月31日(火) 16:00 - 17:00

ビバリン・ウイリアムス (Postdoctoral Fellow, School of Mathematics, University of Leeds, UK)

Inhalational anthrax, caused by the bacterium Bacillus anthracis, is a disease with very high fatality rates. Due to the significant risk posed if the bacterium was to be intentionally used as a bioweapon, it is important to be able to defend against such an attack and to make optimal decisions about treatment strategies. Mechanistic mathematical models can help to quantify and improve understanding of the underlying mechanisms of the infection. In this talk, I will present a multi-scale mathematical model for the infection dynamics of inhalational anthrax. This approach involves constructing individual models for the intracellular, within-host, and population-level infection dynamics, to define key quantities characterising infection at each level, which can be used to link dynamics across scales. I will begin by introducing a model for the intracellular infection dynamics of B. anthracis, which describes the interaction between B. anthracis spores and host cells. The model can be used to predict the distribution of outcomes from this host-pathogen interaction. For example, it can be used to estimate the number of bacteria released upon rupture of an infected phagocyte, as well as the timing of phagocyte rupture and bacterial release. Next, I will show how these key outputs can be used to connect the intracellular model to a model of the infection at the within-host scale. The within-host model aims to provide an overall understanding of the early progression of the infection, and is parametrised with infection data from studies of rabbits and guinea pigs. Furthermore, this model allows the probability of infection and the time to infection to be calculated. Building a model that offers a realistic mechanistic description of these different animal responses to the inhalation of B. anthracis spores is an important step towards eventually extrapolating the model to describe the dynamics of human infection. This would enable predictions of how many individuals would become infected in different exposure scenarios and also on what timescale this would occur.

会場: via Zoom / 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

International Workshop on Blockchain Technology: Blockchain Kaigi 2023 (BCK23)

2023年10月28日(土) - 29日(日)

The International workshop Blockchain Kaigi (Kaigi: Meeting, Conference) aims to bring together researchers and practitioners from various communities of science and technology working on areas related to FinTech, crypto-asset, and blockchain. On February 17th – 18th of 2021 the international workshop “Blockchain in Kyoto 2021 (BCK21)” was held at Kyoto University, and the following year on August 4th – 5th the international workshop “BCK22: Blockchain Kaigi 2022” was held at Tohoku University, both gathered many participants from all over the world and ended successfully. As the third step, the international workshop “BCK23: Blockchain Kaigi 2023” will be held on October 28th -29th, 2023 at RIKEN’s Kobe Campus (Kobe City). Topics for this international conference include, but are not limited to the following. Crypto assets, cryptocurrencies Blockchain technology, cryptography/mathematics B2B and B2C solutions Anomaly detection, cyber security Digital Asset Market, Central Bank Digital Currency CBDC smart contract Application to energy and environmental problems Application to financial inclusion, remittance and digital identity Innovation policy Legal and regulatory issues Network Science, Graph Theory, Mathematics of Hypergraphs

会場: SUURI-COOL (Kobe)

イベント公式言語: 英語

Searching for dark neutrinos through exotic Higgs decays at the ILC

2023年10月24日(火) 16:30 - 17:30

Simon Thor (Ph.D. Student, KTH Royal Institute of Technology, Sweden)

In this study we investigate the feasibility of detecting heavy dark neutrinos ($N_d$) through exotic Higgs decays at the proposed International Linear Collider (ILC), specifically in the channel of $e^+ e^- \to qq~ H$ with $H\to \nu N_d \to \nu~lW \to \nu l~qq$. Analyses based on full detector simulations of the ILD are performed at the center-of-mass energy of 250 GeV for two different beam polarization schemes with a total integrated luminosity of 2 $\mathrm{ab}^{-1}$. A range of dark neutrino masses between the $Z$ boson and Higgs boson masses are studied. The $2\sigma$ significance reach for the joint branching ratio of $BR(H\to\nu N_d)\cdot BR(N_d\to lW)$ is about 0.1\%, nearly independent of the dark neutrino masses, while the $5\sigma$ discovery is possible at a branching ratio of $0.3\%$. Interpreting these results in terms of constraints on the mixing parameters $|\varepsilon_{id}|^2$ between SM neutrinos and the dark neutrino, it is expected to have a factor of 10 improvement from current constraints.

会場: via Zoom

イベント公式言語: 英語

Topological Aspect of Adsorption Site Selectivity on Metal Surfaces

2023年10月24日(火) 13:30 - 15:00

辻 雄太 (九州大学 総合理工学研究院 准教授)

In this talk, the presenter will discuss which adsorption structure is preferred in the adsorption of atoms and molecules on metal surfaces based on the topology of the adsorption structures. The method of moments is used to analyze the electronic density of states of the surface. The third-order moment, which characterizes the skewness of the distribution of the electronic density of states, is related to the topology of the triangles at the adsorption interface. By further relating this to the change in energy of the system with the change in electron occupancy of the states, it is shown that it is possible to discuss the relationship between the type of metal and the topological features of the energetically stable adsorption structure.

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

A cluster algebra structure in the quantum cohomology ring of a quiver variety

2023年10月24日(火) 10:00 - 11:30

Yingchun Zhang (Postdoctoral Researcher, Institute for Advanced Study in Mathematics, Zhejiang University, China)

The Gromov-Witten theory of a quiver variety is expected to be preserved by quiver mutation according to Seiberg duality, which has been proved to be true for A-type and star-shaped quivers. Cluster algebra can be constructed for a given quiver via quiver mutation. The two subjects Gromov-Witten and cluster algebra seem to differ a lot. Howerver, when we move to the quantum cohomology ring of a quiver variety, Benini-Park-Zhao’s work “indicates” that there should be a cluster algebra structure in the quantum cohomology ring of the quiver variety. In this talk, I will introduce our recent work about the construction of such a cluster algebra structure in the quantum cohomology of a quiver variety. In particular, we will give a proof of the construction for A-type cluster algebra in quantum cohomology of a flag variety. This is a joint work with Weiqiang He.

会場: セミナー室 (359号室)

イベント公式言語: 英語

Toward inferring the equation of state from gravitational-wave astronomy

2023年10月18日(水) 14:30 - 16:00

久德 浩太郎 (京都大学 大学院理学研究科 准教授)

The property of supranuclear-density matter is an important question to be answered in QCD. One promising avenue is to study neutron stars with astronomical observations. For this purpose, gravitational waves have become an important tool after GW170817 that delivered information about the matter at a few times the saturation density. If future detectors improve the sensitivity at high frequency, we may be able to investigate the phase structure at further higher density via observations of postmerger gravitational waves or the absence thereof. In this talk, I will review the current understanding of the neutron-star equation of state and then discuss possible future directions based on our binary merger simulation. This seminar is a part of UKAKUREN seminar and jointly held by GW-EOS WG in iTHEMS.

会場: via Zoom / セミナー室 (359号室)

イベント公式言語: 英語

Introduction to F-Theory

2023年10月18日(水) - 20日(金)

溝口 俊弥 (高エネルギー加速器研究機構 (KEK) 准教授)

This is the fifth event hosted by the Quantum Gravity Gatherings (QGG) Study Group at RIKEN iTHEMS. For this event, we have invited Professor Shun'ya Mizoguchi from KEK, Tsukuba, to deliver pedagogical lectures on the F-theory and its relation to particle physics. We aim for this event to provide insights to researchers in related fields. Originally, heterotic string theory was a promising candidate for describing our world, as it naturally incorporated Grand Unified Theory (GUT) based on an exceptional gauge group. However, heterotic theory encounters challenges in moduli fixing. On the other hand, type II theory has an advantage in moduli fixing, but realizing GUT proves to be challenging. The F-theory describes the strongly coupled type IIB string theory, fully utilizing string dualities. This theory appears to realize both the moduli fixing and GUT. Consequently, F-theory plays a central role in string phenomenology. Shun'ya is a leading expert in these areas. We are fortunate to have the opportunity to learn numerous insights into string theory as well as particle physics. This intensive lecture series is designed to be an interactive event. To facilitate this, the number of participants will be limited to approximately 30. The intensive talk will be given in a face-to-face blackboard style (in English, no online streaming) to encourage informal and lively Q&A discussions. The program will also include short talk sessions, where participants can present a 5-minute talk on a topic of their choice, including their research, reviews of specific works, or future study interests.

会場: 研究本館 4階 435-437号室

イベント公式言語: 英語