165 events in 2023

Early Formation of Dark Matter Halos
November 24 (Fri) at 14:00  15:15, 2023
Derek Beattie Inman (Research Scientist, iTHEMS)
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.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English

Seminar
Volume complexity of de Sitter bubbles
November 22 (Wed) at 16:00  17:30, 2023
Nicolò Zenoni (Project Researcher, Department of Physics, Osaka University)
Holographic complexity is conjectured to probe the evolution of spacetime. For black holes in antide 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 threedimensional asymptotically antide 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.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English

X's Fast and Slow
November 21 (Tue) at 16:00  17:00, 2023
Thomas Hitchcock (Special Postdoctoral Researcher, iTHEMS)
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 nonmodel systems, particularly focusing on fungus gnats and pea aphids.
Venue: via Zoom
Event Official Language: English

Bridging physics and society: A case study of collective memory dynamics by socioeconophysics approach
November 20 (Mon) at 15:00  16:30, 2023
Yukie Sano (Associate Professor, Institute of Systems and Information Engineering, University of Tsukuba)
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 socialeconomic phenomena, a field known as socioeconophysics. 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 socioeconophysics.
Venue: Okochi Hall / via Zoom
Event Official Language: English

The 24th MACS Colloquium
November 20 (Mon) at 14:45  18:00, 2023
Satoshi Horike (Professor, Department of Chemistry, Graduate School of Science, Kyoto University)
Yoshihiro Morishita (Team Leader, Laboratory for Developmental Morphogeometry, RIKEN Center for Biosystems Dynamics Research (BDR))14:4515:00 Teatime discussion 15:0016:00 Talk by Dr. Satoshi Horike (Professor, Department of Chemistry, Graduate School of Science, Kyoto University) Title: Material science of new glasses of metalmolecular architectures Abstract: The three major materials  ceramics, metals and organic polymers  all form glass phases and underpin our daily lives and industry. Unlike crystals, glasses have a random structure and designing their molecular structures and properties is still a major challenge. In this talk, I will present research on new glasses made of metals and molecules. It will discuss how the glasses are designed and synthesised, as well as the unique glass structures and functions that result from the metalmolecule chemical bonds. 16:1517:15 Talk by Prof. Yoshihiro Morishita (RIKEN Center for Biosystems Dynamics Research, Team leader) Title: Optimal coding design of positional information and an appropriate spacetime coordinate system to capture an archetype of organ morphogenetic dynamics Abstract: We are engaged in developmental biology research at the intersection of experimentation and theory, driven by a curiosity to understand the laws governing organogenesis. Ideally, we aim to mathematically represent these laws and find commonalities across species and organs. In this seminar, I will present research on a coding design of spatial information within developing tissues, as well as propose spacetime coordinates to directly and quantitatively compare the morphogenetic dynamics of homologous organs across species with different sizes and developmental rates. Furthermore, we will introduce results suggesting the existence of speceisindependent morphogenetic dynamics (a kind of archetype) achieved by applying these methods to biological data. 17:1518:00 Discussion
Venue: Maskawa Hall, 1F, Maskawa Building for Education and Research
Event Official Language: Japanese

6th QGG Intensive Lectures: Introduction to thermalization in isolated quantum systems
November 20 (Mon)  21 (Tue), 2023
Ryusuke Hamazaki (RIKEN Hakubi Team Leader, Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team, RIKEN Cluster for Pioneering Research (CPR))
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 nonequilibrium 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 facetoface 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 5minute talk on a topic of their choice, which could be about their own research, reviews of specific works, or future study interests.
Venue: #435437, Main Research Building
Event Official Language: English

Seminar
Introduction and prospects of topological recursion
November 17 (Fri) at 15:00  17:00, 2023
Osuga Kento (JSPS Research Fellow PD, Graduate School of Mathematical Sciences, The University of Tokyo)
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.
Venue: Seminar Room #359
Event Official Language: English

Seminar
Geometry of special nilpotent orbits
November 15 (Wed) at 14:00  15:30, 2023
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.
Venue: via Zoom
Event Official Language: English

MCME SYMPOSIUM 2023
November 15 (Wed)  16 (Thu), 2023
Kyosuke Adachi (Research Scientist, iTHEMS)
Hiroshi Kokubu (Executive VicePresident, Kyoto University)
Masaru Hongo (Assistant Professor, Department of Physics, Faculty of Science, Niigata University)"MCME SYMPOSIUM 2023" will be held at the Musashino Center of Mathematical Engineering (MCME), Musashino University. This symposium is free of charge and open to everyone. Colleagues of iTHEMS will also be speaking. Below is an excerpt from the program. Wednesday, November 15, 11:20  12:30 Kyosuke Adachi Wednesday, November 15, 16:20  17:30 Hiroshi Kokubu Thursday, November 16, 10:00  11:10 Masaru Hongo Registration is open until November 14. Please register from the related links below. Organized by Musashino Center of Mathematical Engineering (MCME), Musashino University Coorganized by RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS)
Venue: Hybrid Format (Room 301, Building 5, Ariake Campus, Musashino University and Zoom)

Workshop
iTHEMS Graphtheory workshop: from basics to applications
November 13 (Mon)  14 (Tue), 2023
Momoko Hayamizu (Assistant Professor, Faculty of Science and Engineering, School of Fundamental Science and Engineering, Waseda University / PRESTO Researcher, Japan Science and Technology Agency (JST))
Seiya Negami (Professor Emeritus, Yokohama National University)
Takashi Okada (ProgramSpecific Associate Professor, Institute for Life And Medical Sciences, Kyoto University)
Tasuku Soma (Associate Professor, Department of Statistical Inference and Mathematics, The Institute of Statistical Mathematics / Associate Professor, Statistical Science Program, The Graduate University for Advanced Studies (SOKENDAI))
Shun'ichi Azuma (Professor, Garduate School of Informatics, Kyoto University)We will hold a twoday workshop on graph theory, which covers a variety of topics including basic concepts and theorems in graphtheory; graphembedding; phylogenetic tree construction; chemical reaction networks; and cactus network theory. The details are found in the website linked below.
Venue: #435437, Main Research Building
Event Official Language: English

Seminar
Vortex Reconnection in Classical and Quantum Fluids
November 10 (Fri) at 15:00  16:30, 2023
Yoshifumi Kimura (Professor, Graduate School of Mathematics, Nagoya University)
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 NavierStokes 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].
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English

Patterns of fern community assembly throughout the American continent: Do the mechanisms of species diversification also vary with latitude?
November 7 (Tue) at 16:00  17:00, 2023
José Said GutiérrezOrtega (Special Postdoctoral Researcher, iTHEMS)
The global latitudinal gradient of biodiversity, a pattern suggesting that the lowlatitude (tropical) areas have more species than the highlatitude (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.
Venue: via Zoom
Event Official Language: English

Seminar
Compact Star Solutions Beyond General Relativity
November 7 (Tue) at 13:30  15:00, 2023
Kota Numajiri (Ph.D. Student, Graduate School of Science, Nagoya University)
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 nontrivial 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.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English

Mathematical modelling of the host response to inhalational anthrax across different scales
October 31 (Tue) at 16:00  17:00, 2023
Bevelynn Williams (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.
Venue: via Zoom / Hybrid Format (3F #359 and Zoom), Main Research Building
Event Official Language: English

International Workshop on Blockchain Technology: Blockchain Kaigi 2023 (BCK23)
October 28 (Sat)  29 (Sun), 2023
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, cryptoasset, 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
Venue: 8F, SUURICOOL (Kobe)
Event Official Language: English

Seminar
Searching for dark neutrinos through exotic Higgs decays at the ILC
October 24 (Tue) at 16:30  17:30, 2023
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 centerofmass 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.
Venue: via Zoom
Event Official Language: English

Seminar
Topological Aspect of Adsorption Site Selectivity on Metal Surfaces
October 24 (Tue) at 13:30  15:00, 2023
Yuta Tsuji (Associate Professor, Faculty of Engineering Sciences, Kyushu University)
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.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English

Seminar
A cluster algebra structure in the quantum cohomology ring of a quiver variety
October 24 (Tue) at 10:00  11:30, 2023
Yingchun Zhang (Postdoctoral Researcher, Institute for Advanced Study in Mathematics, Zhejiang University, China)
The GromovWitten 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 Atype and starshaped quivers. Cluster algebra can be constructed for a given quiver via quiver mutation. The two subjects GromovWitten and cluster algebra seem to differ a lot. Howerver, when we move to the quantum cohomology ring of a quiver variety, BeniniParkZhao’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 Atype cluster algebra in quantum cohomology of a flag variety. This is a joint work with Weiqiang He.
Venue: Seminar Room #359
Event Official Language: English

Toward inferring the equation of state from gravitationalwave astronomy
October 18 (Wed) at 14:30  16:00, 2023
Koutarou Kyutoku (Associate Professor, Graduate School of Science, Kyoto University)
The property of supranucleardensity 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 neutronstar 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 GWEOS WG in iTHEMS.
Venue: via Zoom / Seminar Room #359
Event Official Language: English

Workshop
Introduction to FTheory
October 18 (Wed)  20 (Fri), 2023
Shun'ya Mizoguchi (Associate Professor, High Energy Accelerator Research Organization (KEK))
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 Ftheory 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 Ftheory describes the strongly coupled type IIB string theory, fully utilizing string dualities. This theory appears to realize both the moduli fixing and GUT. Consequently, Ftheory 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 facetoface 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 5minute talk on a topic of their choice, including their research, reviews of specific works, or future study interests.
Venue: #435437, 4F, Main Research Building
Event Official Language: English
165 events in 2023
Events
Categories
series
 iTHEMS Colloquium
 MACS Colloquium
 iTHEMS Seminar
 iTHEMS Math Seminar
 DMWG Seminar
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 iTHEMS Theoretical Physics Seminar
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 Theory of Operator Algebras
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