セミナー
528 イベント

セミナー
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―・インマン (数理創造プログラム 研究員)
Cosmological observations have led to an extremely precise understanding of the largescale structure of the Universe. A common assumption is to extrapolate largescale properties to smaller scales; however, whether this is correct or not is unknown and many wellmotivated 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 matterradiation 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

セミナー
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 multiscale mathematical model for the infection dynamics of inhalational anthrax. This approach involves constructing individual models for the intracellular, withinhost, and populationlevel 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 hostpathogen 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 withinhost scale. The withinhost 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

セミナー
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 thirdorder 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

セミナー
Progenitors and Explosion Properties of Supernova Remnants Hosting Central Compact Objects
2023年10月6日(金) 10:00  11:30
チェルシー・ブラウン (Ph.D. Student, Department of Physics and Astronomy, University of Manitoba, Canada)
Presented is a systematic, global study of Galactic supernova remnants (SNRs) hosting Central Compact Objects (CCOs) aimed at addressing their explosion properties and supernova progenitors. With the Chandra and XMMNewton telescopes, a spatially resolved Xray spectroscopy study is performed on seven SNRs that show evidence of shockheated ejecta. Using an algorithm, we segmented each SNR in the sample into regions of similar surface brightness. These regions were fit with one or twocomponent plasma shock model(s) in order to separate the forwardshocked interstellar medium from the reverse shockheated ejecta which peak in the Xray bands for elements including O, Ne, Mg, Si, S, Ar, Ca, and Fe. We subsequently derived the explosion properties for each SNR in the sample and found overall low explosion energies (<10^51 erg). To address their progenitor mass, we compare the measured abundances from our spectroscopic modelling to five of the most widely used explosion models and a relatively new electroncapture supernova model. Additionally, we explore degeneracy in the explosion energy and its effects on the progenitor mass estimates. However, no explosion models match all of the measured ejecta abundances for any of the SNRs in our sample. Therefore, we present our best progenitor mass estimates and find overall low progenitor masses (<=25 solar masses) and we highlight the discrepancies between the observed data and the theoretical explosion models.
会場: via Zoom
イベント公式言語: 英語

セミナー
Response to sounds in the cochlea of the inner ear
2023年9月26日(火) 16:00  17:00
太田 岳 (大阪大学 大学院医学系研究科薬理学講座統合薬理学 助教)
We hear sounds. The acoustic wave passes through the ear canal and oscillates the ear drum. The middle ear bones conduct the mechanical input into the cochlea, the primary sensory organ of hearing. A sensory epithelium, a sheetlike tissue inside the snaillike structure, decomposes the sound frequencies into each component along the coil. The sound stimulation evokes nanometerscale motions in the epithelium which contains hair cells. The cells expose their hair bundles to endolymph, the extracellular solution characterized by high [K+]. The epithelium vibration changes the open probability of mechanosensitive channels on the bundles and modulates the ion entering from the fluid. Inner hair cells release neurotransmitters to the auditory nerves and outer hair cells shrink and elongate their soma depending on the receptor potentials. The electromotive response amplifies the vibration of the sensory epithelium and contributes to the faint sound sensitivity and sharp frequency selectivity. With developed technique, we observed the soundevoked vibrations in the sensory epithelium. In this seminar, I will introduce the physiological background of the cochlear physics and the recent results.
会場: via Zoom
イベント公式言語: 英語

セミナー
Thermal production eV dark matter with boseenhancement
2023年9月25日(月) 15:00  16:30
殷 文 (東北大学 大学院理学研究科 物理学専攻 助教)
A very simple production mechanism of feebly interacting dark matter (DM) that rarely annihilates is thermal production, which predicts the DM mass around eV. This has been widely known as the hot DM scenario. Despite there are several observational hints from background lights suggesting a DM in this mass range, the hot DM scenario has been considered strongly in tension with the structure formation of our Universe. In this talk, I show that the previous conclusions are not always true depending on the reaction for bosonic DM because of the Boseenhanced reaction at very low momentum. By utilizing a simple $1 \leftrightarrow 2$ decay/inverse decay process to produce DM, I demonstrate that eV range bosonic DM can be thermally produced in a cold manner from a hot plasma. I also discuss some caveats arising from this phenomenon in the freezein production of DM, and present a related system that can suppress the hot plasma with thermal reaction.
会場: via Zoom
イベント公式言語: 英語

セミナー
First Xray polarimetry of neutron stars with strong magnetic fields
2023年9月25日(月) 13:30  15:00
玉川 徹 (理化学研究所 開拓研究本部 (CPR) 玉川高エネルギー宇宙物理研究室 主任研究員)
We launched the world's first highly sensitive Xray polarimetry satellite, IXPE, in December 2021. IXPE began observations in January 2022 and detected significant Xpolarization from objects in all categories. The IXPE observations have opened a new window in astrophysics. In this talk, I will introduce IXPE and present the results of Xray polarimetry observations of neutron stars with strong magnetic fields (magnetars and neutron star binaries). The neutron star observations show results quite different from our prior expectations and await further theoretical 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

セミナー
Induced gravitational waves from inflaton oscillons
2023年9月22日(金) 14:00  15:30
カロイアン・ディミトロフ・ロザノフ (東京大学 カブリ数物連携宇宙研究機構 (Kavli IPMU) 特任研究員)
We present a new way to study cosmic inflation with gravitational waves. The gravitational signal is generated thanks to nonlinear structures in the inflaton field, called oscillons. This novel probe allows us to test models of inflation which are challenging to test with CMB experiments.
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

Spider silk big data drives the creation of targeted biopolymers from polymerization to biodegradation
2023年9月20日(水) 13:30  15:00
沼田 圭司 (京都大学 大学院工学研究科 教授)
Our Material DX research project (http://pixy.polym.kyotou.ac.jp/ku_numata/index.html) is dedicated to addressing challenges in the design and synthesis of polymeric materials. Our primary objective is to establish a comprehensive material research and technical platform built upon a polymer database. Our efforts center on the creation and advancement of bioadaptive materials featuring biological functionalities and physical properties.1,2 Within the domain of polymer science, the integration of material informatics (MI) for establishing correlations between material structure and properties, along with the utilization of extensive databases, has not witnessed substantial advancement in recent times. Structural protein such as spider silk is an eco and biofriendly polymer as well as one of the key factors to realize the unique properties and functions of natural tissues and organisms.3,4 However, use of structural proteins as structural materials in human life is still challenging. Spider silks are among the toughest known materials and thus provide models for renewable, biodegradable and sustainable biopolymers. However, the entirety of their diversity still remains elusive, and silks that exceed the performance limits of industrial fibers are constantly being discovered. We obtained transcriptome assemblies from 1,098 species of spiders to comprehensively catalog silk gene sequences and measured the mechanical, thermal, structural, and hydration properties of the dragline silks of 446 species.5 The combination of these silk protein genotypephenotype data revealed essential contributions of multicomponent structures in highperformance dragline silks as well as numerous amino acid motifs contributing to each of the measured properties. We hope that our global sampling, comprehensive testing, integrated analysis and open data will provide a solid starting point for future biomaterial designs.
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

セミナー
Predicting future biodiversity with species distribution models: current applications, persistent issues, and where to go from here
2023年9月19日(火) 16:00  17:00
ジェイミイ・キャス (東北大学 大学院理学研究科 准教授)
There is much current interest in macroecology to make predictions of future biodiversity patterns in order to inform both regional and global priorities for conservation and sustainability of ecosystem functions and services. Species distribution models use data on species' occurrence records, environmental predictor variables, and sometimes other data sources to estimate niche relationships and distribution extents—these models can also be combined to make biodiversity estimates. As the field of species distribution modeling has grown considerably over the past two decades, many approaches now exist to build models, evaluate their performance, and use them to make predictions for unsampled areas and times. I will provide an overview of current techniques to predict future distributions of species and biodiversity, detail some issues with these techniques concerning uncertainty and realism of predictions, and contribute my humble thoughts on where the field should go from here.
会場: via Zoom
イベント公式言語: 英語

セミナー
Classification of Meromorphic Spin 2dimensional Conformal Field Theories of Central Charge 24
2023年9月19日(火) 15:00  16:30
Möller Sven (Group Leader, Department of Mathematics, University of Hamburg, Germany)
We classify the selfdual (or holomorphic) vertex operator superalgebras (SVOAs) of central charge 24, or in physics parlance the purely leftmoving, spin 2dimensional conformal field theories with just one primary field. There are exactly 969 such SVOAs under suitable regularity assumptions and the assumption that the shorter moonshine module VB^# is the unique selfdual SVOA of central charge 23.5 whose weight1/2 and weight1 spaces vanish. Additionally, there might be selfdual SVOAs arising as "fake copies" of VB^# tensored with a free fermion F. We construct and classify the selfdual SVOAs by determining the 2neighbourhood graph of the selfdual (purely bosonic) VOAs of central charge 24 and also by realising them as simplecurrent extensions of a dual pair containing a certain maximal lattice VOA. We show that all SVOAs besides VB^# x F and potential fake copies thereof stem from elements of the Conway group Co_0, the automorphism group of the Leech lattice. By splitting off free fermions F, if possible, we obtain the classification for all central charges less than or equal to 24. This is based on joint work with Gerald Höhn (arXiv:2303.17190)
会場: セミナー室 (359号室)
イベント公式言語: 英語

セミナー
Quantum skyrmion Hall effect
2023年9月14日(木) 17:00  18:15
Ashley Cook (Group Leader, Correlations and Topology, Max Planck Institute for the Physics of Complex Systems and Max Planck Institute for Chemical Physics of Solids, Germany)
Field: condensed matter physics Keywords: topology, electronbased quantum skyrmions, spin, Berry curvature Abstract: Topological skyrmion phases of matter are recentlyintroduced topological phases of electronic systems in equilibrium, in which a system with more than one degree of freedom (e.g. spin and orbital degrees of freedom) realizes a topological state for a subset of the degrees of freedom (e.g. only spin). For topological skyrmion phases of spin, this topology is relevant even if spin is not conserved due to nonnegligible atomic spinorbit coupling, and is distinguished by a skyrmion forming in the spin texture over the Brillouin zone, distinct from a skyrmion forming in the texture of the projector onto occupied states over the Brillouin zone. We present results on three band Bloch Hamiltonians realizing this nontrivial spin topology, and outline some bulkboundary correspondence features, such as gapless edge states corresponding to zero net charge—but finite spin angular momentum—pumped across the bulk gap. Tracing out the orbital degree of freedom, we can identify this spin pumping with pumping of spin point charges, and local curvature of the kspace spin skyrmion with a Berry curvature of these spin point charges. That is, the spin pumping is identified with pumping of spin magnetic skyrmions, which reduce to point magnetic charges after tracing out the orbital degree of freedom. We therefore identify topological skyrmion phases as lattice counterparts of quantized transport of quantum magnetic skyrmions, a quantum skyrmion Hall effect. This indicates that the theory of the quantum Hall effect must be generalized, by relaxing the assumption of point charges.
会場: via Zoom
イベント公式言語: 英語

セミナー
QuasiBPS categories
2023年9月13日(水) 10:00  11:30
戸田 幸伸 (東京大学 カブリ数物連携宇宙研究機構 (Kavli IPMU) 教授)
In this talk, I will explain the notion of "QuasiBPS category". This is the (yet to be defined) category which categorifies BPS invariants on CalabiYau 3folds, and plays an important role in categorical wallcrossing in DonaldsonThomas theory. I will explain the motivation of quasiBPS categories, give definition in the case of symmetric quivers with potential (a local model of CY 3folds), and their properties. If time permits, I will explain quasiBPS categories for local K3 surfaces and their relation to derived categories of hyperkahler manifolds. This is a joint work in progress with Tudor Padurariu.
会場: セミナー室 (359号室)
イベント公式言語: 英語

Parameter Fitting for Glucose Homeostasis  Searching for Methods to Predict and Diagnose
2023年9月12日(火) 16:00  17:00
ガブリエル・グレス (東北大学 材料科学高等研究所 (AIMR) 数学連携グループ 特任研究員)
The human body regulates glucose through a complex web of biological interactions, for which stateoftheart models require dozens of variables and parameters to even emulate. But while we've had devices to measure glucose levels as far back as the 1980's, nearly all of the remaining variables and parameters cannot be measured directly to this day. While continuous glucose monitors have greatly improved the health of diabetic patients, there are still many barriers in the diagnosis of atrisk patients as well as accurately dispersing insulin to counteract future trends in glucose levels. While glucose readings are only a small window into one of many factors of how the human body maintains glucose homeostasis, we search for ways to leverage the highfrequency and highvolume data to improve the state of diagnosis and prediction in diabetic patients.
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

セミナー
Collective Plasma Effects in Relativistic RadiationMediated Blast Waves
2023年9月8日(金) 14:00  15:15
Arno Vanthieghem (PrincetonNINS Postdoctoral Research Fellow, Department of Astrophysical Sciences, Princeton University, USA)
Relativistic radiationmediated shocks (RRMS) dictate the early emission in numerous transient sources such as supernovae, low luminosity gammaray bursts, binary neutron star mergers, and tidal disruption events. These shock waves are mediated by Compton scattering and copious electronpositron pair creation. It has been pointed out that a high pair multiplicity inside the shock transition leads to a leptonbaryon velocity separation, prone to plasma instabilities. The interaction of the different species with this radiationmediated microturbulence can lead to coupling and heating that is unaccounted for by current singlefluid models. Here, we present a theoretical analysis of the hierarchy of plasma microinstabilities growing in an electronion plasma loaded with pairs and subject to a radiation force. Our results are validated by particleincell simulations that probe the nonlinear regime of the instabilities and the leptonbaryon coupling in the microturbulent electromagnetic field. Based on this analysis, we derive a reduced transport equation for the particles that demonstrates anomalous coupling of the species and heating in a Joulelike process by the joined contributions of the decelerating turbulence, radiation force, and electrostatic field. We will then discuss the effect of finite magnetization on the general dynamics and recent efforts toward a more selfconsistent description of the coupling. In general, our results suggest that radiationmediated microturbulence could have important consequences for the radiative signatures of RRMS.
会場: via Zoom
イベント公式言語: 英語

セミナー
The Cosmic Gravitational Microwave Background
2023年9月6日(水) 15:00  16:30
イヤン・シュテエグ (数理創造プログラム 特別研究員)
The thermal plasma in the early universe produced a guaranteed stochastic gravitational wave (GW) background, which peaks today in the microwave regime and was dubbed the cosmic gravitational microwave background (CGMB). I show that the CGMB spectrum encodes fundamental information about particle physics and gravity at ultra high energies. In particular, one can determine from the CGMB spectrum the maximum temperature of the universe and the effective degrees of freedom at the maximum temperature. I also discuss briefly how quantum gravity effects arise in the CGMB spectrum as corrections to the leading order result.
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

セミナー
MNISQ: A LargeScale Quantum Circuit Dataset for Machine Learning on/for Quantum Computers in the NISQ era
2023年8月29日(火) 14:00  15:30
Leonardo Placidi (大阪大学 大学院基礎工学研究科 博士課程)
We introduce the first largescale dataset, MNISQ, for both the Quantum and the Classical Machine Learning community during the Noisy IntermediateScale Quantum era. MNISQ consists of 4,950,000 data points organized in 9 subdatasets. Building our dataset from the quantum encoding of classical information (e.g., MNIST dataset), we deliver a dataset in a dual form: in quantum form, as circuits, and in classical form, as quantum circuit descriptions (quantum programming language, QASM). In fact, also Machine Learning research related to quantum computers undertakes a dual challenge: enhancing machine learning by exploiting the power of quantum computers, while also leveraging stateoftheart classical machine learning methodologies to help the advancement of quantum computing. Therefore, we perform circuit classification on our dataset, tackling the task with both quantum and classical models. In the quantum endeavor, we test our circuit dataset with Quantum Kernel methods, and we show excellent results with up to 97% accuracy. In the classical world, the underlying quantum mechanical structures within the quantum circuit data are not trivial. Nevertheless, we test our dataset on three classical models: Structured State Space sequence model (S4), Transformer, and LSTM. In particular, the S4 model applied on the tokenized QASM sequences reaches an impressive 77% accuracy. These findings illustrate that quantum circuitrelated datasets are likely to be quantum advantageous, but also that stateoftheart machine learning methodologies can competently classify and recognize quantum circuits. We finally entrust the quantum and classical machine learning community.
会場: 理化学研究所 和光キャンパス (メイン会場) / via Zoom
イベント公式言語: 英語

セミナー
Landscape structure drives ecoevolution in host parasite systems
2023年8月24日(木) 16:00  17:00
Jhelam Deshpande (Ph.D. Student, Biodiversity: dynamics, interactions and conservation team, Institute of Evolutionary Science of Montpellier, France)
As all biological and many artificial systems, hosts and their parasites are most often spatially structured. Besides this highly relevant spatial context, parasites may change through time due to to evolutionary processes, including mutation and selection. These facts imply that we must study hostparasite systems taking into account space and evolution. Past work has mainly focused on simple spatial structures, but how parasites evolve in realistically complex landscapes remains unclear, hampering the translation of theoretical predictions to real ecological systems.Therefore, we here develop an ecoevolutionary metapopulation model of hostparasite interactions in which hosts and parasites disperse through realistically complex spatial graphs. Parasite virulence, a parasite lifehistory trait of central importance that here impacts host reproduction, is able to evolve. Our model therefore captures the ecoevolutionary feedback loop between host demography and parasite evolution in space. In order to gain a general understanding of parasite ecoevolution in space, we analyse our model for spatial networks that represent terrestrial (represented by randomgeometric graphs; RGG) and riverine aquatic (represented by optimal channel networks; OCN) landscapes. We find that evolved virulence is generally a function of host dispersal, with a unimodal relationship in aquatic and a saturating relationship in terrestrial landscape, and this is driven by higher order network properies. Consistent with previous work, we show that our results are driven by kin selection, because dispersal and landscape structure impact both patterns of relatedness and availability of susceptible hosts. Our model yields readily testable predictions, including that terrestrial parasites should be more virulent than aquatic parasites are low dispersal rates and vice versa as dispersal increases. These differences in evolved virulence directly lead to differences in system stability, with more virulent parasites more often leading to host extinction. Thus, in this study we highlight the role of landscape structure in driving ecoevolutionary dynamics of parasites.
会場: via Zoom
イベント公式言語: 英語

Mating system of buckwheat
2023年8月17日(木) 16:00  17:00
ジェフリ・フォーセット (数理創造プログラム 上級研究員)
Buckwheat (soba in Japanese) has a slightly unusual mating system called heterostylous selfincompatibility where two types of individuals coexist, one that produces flowers with a long style (female part of the flower) and short stamen (male part of the flower), and the other that produces flowers with a short style and long stamen. Mating is only successful when it occurs between the different types of individuals. It is a bit similar to sexual dimorphism where males and females coexists but in this case all individuals have both male and female organs. In this talk, I will introduce the basics of this mating system in buckwheat and some work we have been doing. In particular, I will talk about its genetic architecture and some parallels observed with other plants in which a similar mating system evolved independently. The talk will be aimed at nonexperts so nonbiologists are also welcome to attend.
会場: via Zoom
イベント公式言語: 英語
528 イベント
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