ニュース
131件のニュース / 2022年
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2022-07-05
セミナーレポート
Quantum Matter Seminar by Dr. Thore Posske on June 30, 2022
Dr. Thore Posske from the University of Hamburg gave an online seminar about controlling topological quantum effect in spin systems by manipulating the boundary. He first introduced the idea that topology can connect multiple subfields in physics and then showed how a 1D spin chain can be controlled to form a helix or the ground state by manipulating the evolution of the two chain ends. Since the different quantum states can be controlled by the boundary, this is a potential platform for quantum computing to generate distinct quantum states. Furthermore, the boundary idea was extended to 2D spin systems. By properly changing the spins on the edges, a skyrmion can emerge. In the end, the speaker talked about an experimental approach to distinguishing the topological phases in systems with periodic boundary conditions by multi-pulse spectroscopy, and applied these ideas to 1D topological superconductors. Reported by Thore Posske (University of Hamburg) and Ching-Kai Chiu
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2022-07-04
セミナーレポート
ABBL-iTHEMS Joint Astro Seminar by Mr. Tomoki Matsuoka on July 1, 2022
Mr. Tomoki Matsuoka gave an excellent talk on the long-term evolution of a supernova remnant hosting a double neutron star binary. He presented that stellar mass loss is one of the crucial elements determining the fate of core-collapse supernovae progenitors (SNe). Since the material released from the progenitor will be distributed as circumstellar medium (CSM), it can also influence the subsequent evolution of the SN or supernova remnant (SNR). Despite its importance, mass loss histories predicted by stellar evolution models have not been incorporated with modeling for SNRs. As a first step, he investigated the dynamical evolution of an ultra-stripped supernova remnant (USSNR), which originated from a core-collapse SN explosion proposed to be a candidate formation site of a double neutron star binary. By accounting for the mass-loss history of the progenitor binary using a model developed by a previous study, he constructed the large-scale structure of the CSM up to a radius ∼100 pc. Then, he simulated the explosion and subsequent evolution of a USSN surrounded by such a CSM environment. He found that the CSM encompasses a vast region characterized by a hot plasma with a temperature ∼10^8 K located around the termination shock of the wind from the progenitor binary (∼10 pc), and the USSNR blast wave is drastically weakened while penetrating through this hot plasma. Radio continuum emission from a young USSNR is sufficiently bright to be detectable if it inhabits our galaxy but faint compared to the observed Galactic SNRs. In this seminar, he talked about the background of the connection between the models for stellar evolution and SNRs, the details of his methods, and future prospects very well. Reported by Shigehiro Nagataki
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2022-07-04
セミナーレポート
iTHEMS Biology Seminar by Dr. Margie Mayfield on June 30, 2022
Dr. Margie Mayfield (University of Melbourne) gave us a fantastic talk in the special biology seminar, held in a hybrid style at Okouchi Hall. She told us about comparative work on theoretical models and data in wild flowers. We really thank Margie on her great talk, especially despite her very tight schedule in Japan. Thank you Margie! I look forward to seeing you soon in person! Reported by Ryosuke Iritani
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2022-07-04
今週の注目人物Self-introduction: Christy Kelly
Hi, I'm Christy Kelly. I studied physics for my undergraduate degree in London before moving to Edinburgh to do a PhD in theoretical physics at Heriot-Watt university, completed in early 2022. I have now joined iTHEMS as an SPDR. I am interested in gravity, especially coarse aspects of gravity that persist in the absence of differentiable structure; in more physical terms, we can perhaps think of this as gravity in regimes where quantum fluctuations become significant. In such regimes, basic mathematical tools such as calculus are no longer valid and it becomes nontrivial how to characterise even such fundamental notions as curvature. To get around this problem, I hope to exploit the recently flourishing mathematical field of optimal transport theory, which has already become a paradigm for the study of low regularity Riemannian geometry and has seen some very exciting recent developments in the Lorentzian case. Unexpected connections to different fields of physics also arise naturally in the optimal transport theoretic framework: for instance, the Einstein equations can be characterised in terms of the convexity/concavity properties of certain entropy functionals along choice trajectories in spacetime. Optimal transport theory also provides a notion of curvature for networks which has proved of some structural significance; I hope to also take this line of research forward during my time here at iTHEMS.
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2022-06-30
今週の論文Week 5, June 2022
Title: Role of the effective range in the density-induced BEC-BCS crossover Author: Hiroyuki Tajima, Haozhao Liang arXiv: http://arxiv.org/abs/2206.12599v1
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2022-06-28
リサーチニュース
RIKEN Research: Flitting between the wings of a butterfly
Just making small tweaks to certain variables could potentially modify extreme weather events such as sudden downpours, computer simula- tions by two RIKEN researchers have shown. Scientists have long desired to develop ways to control the weather. Research in this area has intensified due to climate change, which is giving rise to more extreme weather events. Present methods for modifying the weather have limited success. Seeding the atmosphere can induce rain, but only when the atmosphere is already in a state where it might rain. Geoen- gineering projects have been envisioned, but they have yet to be conducted due to concerns about unpredicted long-term effects. As a promising approach, Takemasa Miyoshi and Qiwen Sun, both of the RIKEN Center for Computational Science, have looked to chaos theory to assess the possibility of mitigating weather events such as torrential rain by making small changes. Instead of con- sidering the weather system in all its complexity, they focused on a far simpler system—the butterfly attractor. To read more, please see related links.
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2022-06-28
リサーチニュース
RIKEN Research: Worming out of the black-hole information paradox
RIKEN physicist and two colleagues have found that a wormhole—a theoretical bridge connecting distant regions of the Universe—may help to shed light on the mystery of what happens to information about matter consumed by black holes. Einstein’s theory of general relativity predicts that nothing that falls into a black hole can escape its clutches. But in the 1970s, Stephen Hawking calculated that black holes should emit radiation when quantum mechanics, the theory governing the microscopic realm, is considered. “This is called black hole evaporation because the black hole shrinks, just like an evaporating water droplet,” explains Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences. To read more, please see related links.
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2022-06-27
セミナーレポート
iTHEMS Math Seminar by Dr. Shou Yoshikawa on June 10, 2022
On June 10, Shou Yoshikawa gave an introductory talk on his research field. He started his talk by explaining what is an algebraic geometry in mixed characteristic. He then explained some recent results on this subject. Reported by Keita Mikami
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2022-06-23
セミナーレポート
Quantum Matter Seminar by Dr. Nobuyuki Okuma on June 21, 2022
Quantum Matter Study Group invited Prof. Nobuyuki Okuma to give an online seminar about non-Hermitian topological phases. The seminar started with a succinct introduction to non-Hermitian matrices. Different from Hermitian systems, the energy spectra now become complex numbers, the bra and ket states become inequivalent, and the Hamiltonians are not always diagonalizable, leading to the emergence of exceptional points. Taking the Hatano-Nelson model as an example, the speaker studied the 1D chain with the imaginary gauge transformation and showed that the spectra strongly depend on the boundary conditions (being periodic or open). Furthermore, distinct from end modes in Hermitian topological insulators, skin effect arises in non-Hermitian systems, with skin modes accumulating in one end of the chain. He further showed that this skin effect also exhibits topological nature and can be generalized to either higher-dimensional systems or to other non-Hermitian systems with Z2 topological invariants. Reported by Chen-Hsuan Hsu (YITP) and Ching-Kai Chiu
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2022-06-21
セミナーレポート
iTHEMS Biology Seminar by Dr. Mitsusuke Tarama on June 16, 2022
On June 16th, Dr. Tarama gave us an interesting talk about the physical modeling of self-organization in the chick embryo. He first introduced several beautiful patterns in biology such as stripes of pigment cells of Zebrafish. He then explained a recent observation of the dynamical meshwork structure of chick mesodermal cells, which is the direct motivation of his theoretical work. He showed how the intercellular interactions and shape deformation of cells can produce the dynamical meshwork structure, by physical modeling and application of the persistent homology as a useful tool. We are really grateful to Dr. Tarama for his comprehensive talk from both experimental and theoretical sides. Reported by Kyosuke Adachi
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2022-06-20
セミナーレポート
Math-Phys Seminar by Dr. Daisuke Yoshida on June 16, 2022
Dr. Daisuke Yoshida first motivated the expectation that the true quantum gravity, whatever its form turns out to be, should be free from singularities in the universe. The "singularity theorem" by Penrose states that a spacetime singularity arises under a set of certain assumptions. Flipping the argument around, if one admits that singularities are absent in our universe, at least one of the assumptions in the theorem needs to be abandoned. Dr. Yoshida discussed general properties that a non-singular universe must satisfy in order to avoid the singularity theorem. In particular, he found and explained that the universe must be, in some sense, smaller than the corresponding closed de Sitter spacetime. His talk stimulated the audience, and they continued discussions for long after his seminar. Reported by Ryo Namba
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2022-06-16
今週の論文Week 3, June 2022
Title: Reflected Entropy in Boundary/Interface Conformal Field Theory Author: Yuya Kusuki arXiv: http://arxiv.org/abs/2206.04630v1
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2022-06-09
セミナーレポート
iTHEMS Biology Seminar by Dr. José Said Gutiérrez-Ortega on June 2, 2022
In this talk, I mentioned how both geographic isolation and natural selection may influence the way how species can be originated. I made emphasis in a general pattern that suggests that tropical species are more likely than high-latitude species to evolve while retaining the niche of their ancestors; a process called “niche conservatism”. To demonstrate this pattern, I showed the recent results of my own empirical research on the cycad genus Ceratozamia from Mexico: species at lower latitudes evolved niches less differentiated than expected from a Brownian Motion model (an evidence of niche conservatism), and high-latitude species evolved niches more differentiated than expected (an evidence of niche divergence). I hypothesize that both “niche conservatism” and “niche divergence” are not opposed processes as usually thought in ecology, but are part of a same general process. The implementation of models to predict how phylogenetic and ecological factors interplay in the formation of species along the latitudinal gradient may explain the pattern at the global level. The discussion on this topic allowed identifying that the latitude-associated variation of biodiversity richness seems to be analogous to thermodynamic models: a higher energy availability in the tropics will make biological groups to evolve different ways (species) to exploit that energy. Reported by José Said Gutiérrez-Ortega
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2022-06-09
今週の論文Week 2, June 2022
Title: Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs Author: Meng Li, Geng Li, Lu Cao, Xingtai Zhou, Xiancheng Wang, Changqing Jin, Ching-Kai Chiu, Stephen J. Pennycook, Ziqiang Wang, Hong-Jun Gao Journal Reference: Nature (2022) doi: https://doi.org/10.1038/s41586-022-04744-8 Title: Observing Supernova Neutrino Light Curves with Super-Kamiokande. III. Extraction of Mass and Radius of Neutron Stars from Synthetic Data Author: Yudai Suwa, Akira Harada, Masayuki Harada, Yusuke Koshio, Masamitsu Mori, Fumi Nakanishi, Ken'ichiro Nakazato, Kohsuke Sumiyoshi, Roger A. Wendell arXiv: http://arxiv.org/abs/2204.08363v1 Title: Lindbladian Many-Body Localization Author: Ryusuke Hamazaki, Masaya Nakagawa, Taiki Haga, Masahito Ueda arXiv: http://arxiv.org/abs/2206.02984v1 Title: Semiclassical Gravity from Averaged Boundaries in two-dimensional BCFTs Author: Yuya Kusuki arXiv: http://arxiv.org/abs/2206.03035v1 Title: Evaluations of uncertainties in simulations of propagation of ultrahigh-energy cosmic-ray nuclei derived from microscopic nuclear models Author: E. Kido, T. Inakura, M. Kimura, N. Kobayashi, S. Nagataki, N. Shimizu, A. Tamii, Y. Utsuno arXiv: http://arxiv.org/abs/2206.03447v1 Title: Protoneutron Star Convection Simulated with a New General Relativistic Boltzmann Neutrino Radiation-Hydrodynamics Code Author: Ryuichiro Akaho, Akira Harada, Hiroki Nagakura, Wakana Iwakami, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, Kohsuke Sumiyoshi, Shoichi Yamada arXiv: http://arxiv.org/abs/2206.01673v1 Title: Semi-analytical frameworks for subhalos from the smallest to the largest scale Author: Nagisa Hiroshima, Shin'ichiro Ando, Tomoaki Ishiyama arXiv: http://arxiv.org/abs/2206.01358v1 Title: Ring isomorphisms of type II$_\infty$ locally measurable operator algebras Author: Michiya Mori arXiv: http://arxiv.org/abs/2206.00875v1 Title: Universal van der Waals force between heavy polarons in superfluids Author: Keisuke Fujii, Masaru Hongo, Tilman Enss arXiv: http://arxiv.org/abs/2206.01048v1
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2022-06-09
ホットトピック
RIKEN-Berkeley Center was opened
RIKEN iTHEMS and N3AS Physics Frontier Center have started a joint research center, RIKEN-Berkeley Center (RBC), physically located on the 3rd floor of the physics building in Univ. California, Berkeley. This new Center aims to enhance the collaboration on nuclear astrophysics and quantum information science between the two institutions. On May 27-29, 2022, the first annual meeting of N3AS was held in Berkeley together with their international partners, RIKEN iTHEMS and CNRS Centre Pierre Binetruy. iTHEMS members are encouraged to use RBC as a base to interact with researchers in physics, mathematics, biology and related fields at Berkeley.
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2022-06-09
今週の注目人物
Self-introduction: Akira Matsumoto
I am Akira Matsumoto. I was in KEK until March 2022 as a student of SOKENDAI and got my Ph.D. there. Then I came to RIKEN and joined iTHEMS as a postdoctoral researcher in May 2022. I am interested in non-perturbative nature of gauge theories such as quantum chromodynamics (QCD), which describes the dynamics of quarks and gluons. Since these elementary particles are building blocks of matter, QCD is the important key to understanding history of our universe. The most powerful method of studying QCD is the Monte Carlo simulation based on the lattice gauge theory. So, we can simulate the dynamics of QCD on a supercomputer. However, in some cases, the Monte Carlo method is not applicable due to the so-called sign problem. For example, QCD with the chemical potential or with the topological theta term suffer from this problem. Since they are related to the structure of neutron star and the strong CP problem, the sign problem is a major obstacle to understanding such phenomena. I am studying and developing methods to avoid this problem. There are some conventional approaches such as the complex Langevin method and the tensor renormalization group. I am also trying to apply recently developing quantum computation to the simulation of gauge theories. I expect we can overcome the sign problem by using these methods in near future.
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2022-06-08
セミナーレポート
DMWG Seminar by Dr. Shintaro Eijima on June 6, 2022
Dark matter (DM) is one important ingredient of our Universe of which existence indicates the theory beyond the Standard Model. It is not the unique motivation to extend the Standard Model describing the visible world. For example, we need to explain the origin of the tiny neutrino mass and the matter-antimatter asymmetry. The introduction of sterile neutrinos could solve these problems simultaneously. Sterile neutrinos are new species of neutrinos which communicate with the Standard Model neutrino (active neutrinos) through mixing. Unfortunately, the possibility of explaining the whole of DM with the sterile neutrinos is already excluded from observations of X-ray emission, neutrino beam experiments, and cosmological requirements. However, it is still a viable candidate when we consider the production mechanism carefully. Furthermore, some of such scenarios expect large lepton asymmetries resulting in the matter-antimatter asymmetry. The sphaleron process takes an important role in such scenarios and it is related to the electroweak phase transition in the early Universe. The process of fixing the lepton asymmetry is interesting: sterile neutrinos first freeze-in, then freeze-out, and decay. Quantitative prediction of such processes requires sophisticated calculations. Dr. Eijima has shown the latest results in this talk, with the comments that the bottleneck to proceed is the computational costs. The methodology is already well-developed. We will see indicative predictions in the near future! Neutrino physics will open new windows for our Universe! Reported by Nagisa Hiroshima
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2022-06-08
セミナーレポート
ABBL-iTHEMS Joint Astro Seminar by Dr. Kanji Mori on June 3, 2022
Axion-like particles (ALPs) are a class of hypothetical bosons that feebly interact with ordinary matter. The hot plasma of stars and core-collapse supernovae is a possible laboratory to explore physics beyond the standard model, including ALPs. Once produced in a supernova, some of the ALPs can be absorbed by the supernova matter and affect energy transfer. The speaker recently consistently calculated the ALP emission in core-collapse supernovae and the backreaction on supernova dynamics. It is found that the stalled bounce shock can be revived if the coupling between ALPs and photons is as high as $g_{a\gamma}\sim 10^{-9}$ GeV$^{-1}$ and the ALP mass is 40-400 MeV. Reported by Shigehiro Nagataki
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2022-06-08
受賞情報
Dr. Yuki Yokokura received The 13th RIKEN Research Incentive Award (Ohbu Award)
Yuki Yokokura (Senior Research Scientist, iTHEMS) received "The 13th RIKEN Research Incentive Award (Ohbu Award)" on March 23, 2022 for his outstanding achievement in the "Study of Quantum Black Holes". Congratulations!
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2022-06-06
ホットトピック
Ryosuke Iritani was interviewed by The Big Issue of Japan
Ryosuke Iritani (Research Scientist, iTHEMS) is interviewed by The Big Issue Japan, and the latest volume (vol 432) is just published on 1st June. The Big Issue is a magazine dedicated to supporting people in difficult circumstances and helping them achieve self-reliance. Each issue costs 450 yen, out of which 230 yen is the direct income of the street sales staff. The content is about mathematical biology and is accessible for anyone. We hope as many people as possible take it a read and support the people!
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2022-06-06
プレスリリース
進化・生態ダイナミクスの共通法則 －生物の個体群変化を物理学的な関係式で記述する－
理化学研究所（理研）生命機能科学研究センター生体非平衡物理学理研白眉研究チームの足立景亮基礎科学特別研究員（数理創造プログラム基礎科学特別研究員）、理研数理創造プログラムの入谷亮介研究員、濱崎立資上級研究員（開拓研究本部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）の研究チームは、情報理論・統計物理学の手法を用いることで、進化・生態系の個体群ダイナミクスを扱う理論モデルにおいて幅広く成り立つ関係式を提案しました。 本研究成果は、進化や生態系における複雑な個体数の時間的変化を統一的枠組みによって理解することにつながると期待できます。 詳細は関連リンクをご覧ください。
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2022-06-02
今週の論文Week 1, June 2022
Title: Evaporation of Echoing Black Holes Author: Naritaka Oshita, Hayato Motohashi, Sousuke Noda arXiv: http://arxiv.org/abs/2205.15342v1 Title: Viscosity suppresses r-process viable outflows in global models of collapsar disks Author: Oliver Just, Miguel A. Aloy, Martin Obergaulinger, Shigehiro Nagataki arXiv: http://arxiv.org/abs/2205.14158v1 Title: On a singular limit of the Kobayashi--Warren--Carter energy Author: Yoshikazu Giga, Jun Okamoto, Koya Sakakibara, Masaaki Uesaka arXiv: http://arxiv.org/abs/2205.14314v1 Title: Complementarity and causal propagation of decoherence by measurement in relativistic quantum field theories Author: Yoshimasa Hidaka, Satoshi Iso, Kengo Shimada arXiv: http://arxiv.org/abs/2205.08403v2 Title: Angular Momentum Inheritance from the Schwinger Effect in (Chromo)electromagnetic Fields Author: Patrick Copinger, Yoshimasa Hidaka arXiv: http://arxiv.org/abs/2203.10917v1
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2022-05-30
セミナーレポート
Math-Phys Seminar by Dr. Toshifumi Noumi on May 19, 2022
Dr. Toshifumi Noumi (Kobe University) gave a pedagogical seminar on the so-called swampland program in particle physics. The program aims to clarify nontrivial consistency conditions on symmetries in quantum gravity that leave implications for particle physics and cosmology. Dr. Noumi started out with the basic philosophy of the study and expanded the details using the arguments of symmetries, blackholes, holography etc., keeping accessibility for broad audience. Reported by Ryo Namba
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2022-05-30
セミナーレポート
iTHEMS Math Seminar by Dr. Yuto Moriwaki on May 23, 2022
On May 23, there was a math seminar by Yuto Moriwaki. He gave an introductory talk on the mathematical formulation of CFT. Reported by Keita Mikami
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2022-05-30
セミナーレポート
iTHEMS Biology Seminar by Dr. Dan Warren on May 19, 2022
In the Biology Seminar on May 19th, 2022, we had the great opportunity to have Dr. Dan Warren (Okinawa Institute of Science and Technology, Japan) as an invited speaker. In his talk, Dr. Warren explained why the evaluation of species distribution models (SDMs) has become a useful method to understand and predict the geographic distribution of species. In particular, they provide vital information to take measurements in the conservation of biodiversity. To construct SDMs, researchers in this field have taken advantage of publicity available geographic and environmental big data. Usually, those kind of data were not produced with the intention to use it in ecology, but ecologists have developed many methods to use the big data to answer questions in ecology and evolutionary biology. However, despite that several of those methods have become standard in ecology, Dr. Warren warns us that all commonly used methods have serious biases, and such biases might be related to how much we unquestionably rely that big data. To explain his point, he showed the results of one paper that he and his colleagues recently published. In that paper, the authors used occurrence data of a fictional animal: the Pokémon Kangaskhan (name in English) or ガルーラ (in Japanese), and followed the usual methods to construct SDMs in order to predict the Pokémon distribution in the Australian territory. They found that the distribution of the fictional animal has strong biases, and that same patterns of biases are also present in many other real-life species. Dr. Warren concluded that there is a big open field to improve methods to construct SDMs. The incorporation of prior information in the construction of SDMs, and the application of Markov chain Monte Carlo methods to account for the uncertainty of results might be effective solutions to solve the problems that persist in this research field. Reported by José Said Gutiérrez-Ortega
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2022-05-30
セミナーレポート
Seminar by Dr. Teppei Kitahara on May 20, 2022
Dr. Teppei Kitahara from Nagoya University gave a comprehensive review of anomalies from the Standard Model in particle physics. Continuous development of experiments in recent years has revealed a large number of experimental anomalies which the Standard Model cannot explain. It is statistically obvious that as the number of experiments increases, one encounters a new anomaly due to the statistical fluctuation. But interestingly, some of the anomalies have been cross-checked by different experiments. These would be hints for physics beyond the Standard model. In his seminar, he focused on the flavor anomalies (also known as lepton flavor universality violation), the muon g-2 anomaly, and recently measured the W boson mass anomaly. He also discussed these implications for the new physics and introduced several of his works. Reported by Etsuko Itou
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2022-05-26
今週の論文Week 5, May 2022
Title: Reheating after relaxation of large cosmological constant Author: Paul Martens, Shinji Mukohyama, Ryo Namba arXiv: http://arxiv.org/abs/2205.11754v1 Title: Accuracy of one-dimensional approximation in neutron star quasi-normal modes Author: Hajime Sotani arXiv: http://arxiv.org/abs/2205.10523v1 Title: Attractive $N$-$φ$ Interaction and Two-Pion Tail from Lattice QCD near Physical Point Author: Yan Lyu, Takumi Doi, Tetsuo Hatsuda, Yoichi Ikeda, Jie Meng, Kenji Sasaki, Takuya Sugiura arXiv: http://arxiv.org/abs/2205.10544v1
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2022-05-23
セミナーレポート
ABBL-iTHEMS Joint Astro Seminar by Dr. Yannis Liodakis on May 20, 2022
The origin of high-energy neutrinos is fundamental to our understanding of the Universe. Apart from the technical challenges of operating detectors deep below ice, oceans, and lakes, the phenomenological challenges are even greater. The sources are unknown, unpredictable, and we lack clear signatures. Neutrino astronomy therefore represents the greatest challenge faced by the astronomy and physics communities thus far. The possible neutrino sources range from accretion disks and tidal disruption events, through relativistic jets to galaxy clusters with blazar TXS 0506+056 the most compelling association thus far. Since then, immense effort has been put into associating AGN-jets with high-energy neutrinos, but to no avail. The speaker discussed his current efforts in understanding the multimessenger processes in the Universe, and once and for all proving or disproving if AGN-jets are neutrino emitters. Reported by Shigehiro Nagataki
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2022-05-19
今週の論文Week 4, May 2022
Title: Gyrohydrodynamics: Relativistic spinful fluid with strong vorticity Author: Zheng Cao, Koichi Hattori, Masaru Hongo, Xu-Guang Huang, Hidetoshi Taya arXiv: http://arxiv.org/abs/2205.08051v1 Title: Event reconstruction of Compton telescopes using a multi-task neural network Author: Satoshi Takashima, Hirokazu Odaka, Hiroki Yoneda, Yuto Ichinohe, Aya Bamba, Tsuguo Aramaki, Yoshiyuki Inoue arXiv: http://arxiv.org/abs/2205.08082v1 Title: Running Hubble constant from the SNe Ia Pantheon sample? Author: Tiziano Schiavone, Giovanni Montani, Maria Giovanna Dainotti, Biagio De Simone, Enrico Rinaldi, Gaetano Lambiase arXiv: http://arxiv.org/abs/2205.07033v1 Title: The Prime Number Theorem and Pair Correlation of Zeros of the Riemann Zeta-Function Author: D. A. Goldston, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2205.06503v1
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2022-05-18
セミナーレポート
iTHEMS Math Seminar by Dr. Taketo Sano on May 13, 2022
In May 13, there was a math seminar by Taketo Sano. He gave an introductory talk on category theory. Reported by Keita Mikami
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2022-05-09
プレスリリース
巨視的な遷移における速度限界の発見 －連続の式に基づく統一的アプローチ－
理化学研究所（理研）開拓研究本部非平衡統計力学理研白眉研究チームの濱崎立資理研白眉研究チームリーダー（数理創造プログラム上級研究員）は、「巨視的な遷移」を伴うような物理的過程において有用となる「速度限界」、すなわち遷移速度に関する不等式を新たに発見しました。 本研究成果は、量子多体系の熱平衡化の時間スケールなどをはじめとする非平衡統計力学へ示唆を与えると同時に、巨視的な量子系の制御など、近年重要となっている量子技術の基礎的な理解に貢献することが期待できます。 続きは関連リンクをご覧ください。
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2022-05-09
プレスリリース
トンガ海底火山噴火のラム波を鮮明に可視化 －ひまわり8号が捉えた波の全貌－
理化学研究所（理研）計算科学研究センターデータ同化研究チームの三好建正チームリーダー（開拓研究本部三好予測科学研究室主任研究員、数理創造プログラム副プログラムディレクター）、大塚成徳研究員（開拓研究本部三好予測科学研究室研究員、数理創造プログラム研究員）の研究チームは、気象衛星ひまわり8号の画像を用いて、2022年1月に発生したトンガの海底火山噴火に伴う音波の一種である「ラム波」を鮮明に可視化する手法を独自に開発しました。さらに、この画像からラム波を自動抽出する手法を開発し、到達時刻分布や地上気圧観測との関係を明らかにしました。 本研究成果は、火山噴火などに伴う大気波動やそれに伴う潮位変動の科学的理解と実況監視、観測データと大気・海洋の大規模計算との融合によるシミュレーションの高度化や将来的な予測手法の開発に貢献すると期待できます。 続きは関連リンクをご覧ください。
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2022-05-05
今週の論文Week 2, May 2022
Title: High energy emission component, population, and contribution to the extragalactic gamma-ray background of gamma-ray emitting radio galaxies Author: Yasushi Fukazawa, Hiroto Matake, Taishu Kayanoki, Yoshiyuki Inoue, Justin Finke arXiv: http://arxiv.org/abs/2204.14019v1 Title: The $a$-points of the Riemann zeta-function and the functional equation Author: Athanasios Sourmelidis, Jörn Steuding, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2204.13887v1 Title: Speed Limits for Macroscopic Transitions Author: Ryusuke Hamazaki Journal Reference: PRX Quantum 3, 020319 (2022) doi: https://doi.org/10.1103/PRXQuantum.3.020319 arXiv: http://arxiv.org/abs/2110.09716v3
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2022-04-30
セミナーレポート
iTHEMS Biology Seminar by Mr. Daiki Kumakura on April 28, 2022
On April 28th, I talked about the Asgard archaea and the theory of intracellular symbiosis and discussed the mathematical modeling of the symbiosis hypothesis. First, I gave a brief of the classification of the organism as a five-kingdom system and three-domain system. Next, I talked about Asgard archaea, a group of archaea that has received much attention recently. Finally, I discussed the culture of Asgard archaea and the new theory of intracellular symbiosis that has developed as a result. In my presentation, I prepared the idea of mathematical modeling for the new theory. Audience members gave a variety of opinions on this model. In particular, I discussed points where the evolutionary model should be added, whether deterministic or stochastic dominance contributed, and why symbiosis was possible only in two specific species although a variety of symbiotic relationships were possible. I had a meaningful time exchanging opinions and having discussions with various researchers. Thank you so much. Reported by Daiki Kumakura
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2022-04-28
受賞情報
Takemasa Miyoshi and Yuji Sugita received 2022 MEXT Commendation for Science and Technology
Takemasa Miyoshi (R-CCS Team Leader/ iTHEMS Deputy Director) received "2022 MEXT Commendation for Science and Technology" for "Study on Big Data Assimilation to Innovate Numerical Weather Forecasting". Congratulations! Yuji Sugita (CPR Chief Scientist/ iTHEMS Senior Research Scientist) received "2022 MEXT Commendation for Science and Technology" for "Theoretical Study on Dynamic Structure of Biomolecules in the Intracellular Environment". Congratulations!
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2022-04-28
セミナーレポート
iTHEMS Colloquium by Dr. Hong-Yan Shih on April 22, 2022
On April 22 (Fri), we had the first iTHEMS colloquium of FY2022 by inviting Hong-Yan Shih from Academia Sinica, Taiwan. After reviewing the turbulent phenomena in various area of science, she discussed how the turbulence occurs by increasing the flow velocity and how one can develop an effective theory to describe the critical region of laminar-turbulent transition. Then she discussed a remarkable mathematical relation between the effective theory with the predator-prey dynamics in ecology and showed a characteristic super exponential scaling law. The topic was an ideal subject for the interdisciplinary talk, and there were many questions from the researchers with different scientific backgrounds.
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2022-04-28
今週の論文Week 5, April 2022
Title: Visualizing Lamb Waves From a Volcanic Eruption Using Meteorological Satellite Himawari-8 Author: Shigenori Otsuka Journal Reference: Geophysical Research Letters, 49, e2022GL098324 (2022) doi: https://doi.org/10.1029/2022GL098324
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2022-04-28
セミナーレポート
Introduction to Topological Insulators by Dr. Tomoki Ozawa on April, 2022
In this lecture series, Professor Ozawa gave an introduction to topological insulators which are materials whose wavefunctions show nontrivial topological structures in momentum space. In the first two lectures, he introduced the so-called Su-Schrieffer-Heeger model and the bulk-edge correspondence which links edge states with winding number of certain operator in the Hamitonian. Such correspondence has its origin in mathematics called Toeplitz Index theorem which is a special case of Atiyah-Singer index theorem. In the last two lectures, Chern insulators and quantum metrics are introduced. Eigenvectors of the Hamiltonian define a map from the momentum space (typically a torus) to a complex projective space. The pullback Fubini-Study metric (and standard Kahler form) defines the so-called quantum metric (and Berry curvature) on the momentum space. Using Chern-Weil theory, Chern classes/characters are then defined. Chern classes which are originally notions from differential geometry/topology play an important role in topological insulators. A necessary and sufficient condition is also given when the above mentioned map is an immersion and realises momentum space as a Kahler submanifold of the projective space. Reported by Yalong Cao
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2022-04-25
セミナーレポート
iTHEMS Math Seminar by Dr. Cédric Ho Thanh on April 22, 2022
On April 22, there was a math seminar by Dr. Cédric Ho Thanh. In the first half, he explained the recurrence theorems for the topological Markov chain. In the second half, he explained the sketch of the proof. Reported by Keita Mikami
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2022-04-25
リサーチニュース
RIKEN Research: Quantum computing and deep learning could help solve the mysteries of quantum gravity
RIKEN physicists have put quantum computing and deep learning through their paces and found that they are powerful tools for gleaning insights into new theories of quantum gravity [1]. They could thus help solve one of the most formidable challenges in modern physics—developing a theory of gravity that jives with quantum physics. When Einstein nutted out his theory of general relativity in 1915, his only tools were pen and paper. The same was true of the pioneers of quantum theory. But the next major breakthrough in theoretical physics could be made with help from emerging technologies such as quantum computers and machine learning, Enrico Rinaldi of RIKEN Theoretical Quantum Physics Laboratory thinks. “I believe these technologies are poised to transform the way we do theoretical physics,” he says. To read more, please visit the related link.
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2022-04-25
ホットトピック
iTHEMS x academist online event was held on April 24, 2022
As the alternative for the lectures at RIKEN’s annual open house, iTHEMS held another online lecture event for the general public with the help of Academist Inc., on April 24th, 2022. This year, the lectures were Masaki Taniguchi, Hidetoshi Taya, Akira Harada, Yingying and Euki Yazaki, who all gave splendid public lectures accessible even to junior-high school students. Each lecturer also served as a commentator to another lecture, asking questions on behalf of the audience. During the lunch break, Program Director Hatsuda showed the offices of iTHEMS and around. The event was moderated by Ms. Michibayashi from Academist; Her facilitation with a wit kept the event lively. At one time during the event, more than two hundred audiences participated.
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2022-04-25
セミナーレポート
ABBL-iTHEMS Joint Astro Seminar by Dr. Masanori Iwamoto on April 22, 2022
Dr. Masahiro Iwamoto gave a presentation on his recent three-dimensional (3D) particle-in-cell (PIC) simulation of relativistic shocks and application of the results of the 3D-PIC simulations to astrophysical phenomena. For example, the origin of fast radio bursts (FRBs; Lorimer et al. 2007) is one of the unsolved problems in astrophysics. Many observations of FRBs indicate that FRBs must be coherent emission in the sense that coherently moving electrons radiate electromagnetic waves. In relativistic shocks, it is well known that coherent electromagnetic waves are excited by synchrotron maser instability (SMI) in the shock transition (Hoshino & Arons 1991). The SMI is also known as the emission mechanism of coherent radio sources such as auroral kilometric radiation at Earth and Jovian decametric radiation. Recently, some models of fast radio burst based on the coherent emission from relativistic shock via the SMI have been proposed (e.g., Lyubarsky 2014; Beloborodov 2017; Plotnikov & Sironi 2019; Metzger et al. 2019) and the SMI in the context of relativistic shocks attracts more attention from astrophysics. In this seminar, by performing the world’s first 3D-PIC simulation of relativistic shocks, he demonstrated that large-amplitude electromagnetic waves are indeed excited by the SMI even in 3D and that the wave amplitude is significantly amplified and comparable to that in pair plasmas due to a positive feedback process associated with ion-electron coupling. Based on the simulation results, he discussed the applicability of the SMI for FRBs. Reported by Shigehiro Nagataki
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2022-04-22
今週の論文Week 4, April 2022
Title: GRB Prompt Emission: Observed Correlations and Their Interpretations Author: Tyler Parsotan, Hirotaka Ito arXiv: http://arxiv.org/abs/2204.09729v1 Title: Fedder type criteria for quasi-$F$-splitting Author: Tatsuro Kawakami, Teppei Takamatsu, Shou Yoshikawa arXiv: http://arxiv.org/abs/2204.10076v1
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2022-04-20
今週の注目人物
Self-introduction: José Said Gutiérrez-Ortega
¡Hola! This is José (ホセ). I am a Mexican biologist in search of knowledge and interactions with scientists in all disciplines. I obtained my bachelor's degree in Mexico and completed my graduate studies in Japan: two countries where I grew up as a researcher, and where I also had great experiences working in science education. I joined iTHEMS as a SPDR in April 2022, and this transition represented an extraordinary chance for me to expand my research lines and interests. My scientific background is in evolutionary biology and ecology. Therefore, the main questions that motivate my studies are “how is the origin of the species?”, “why are species the way they are?”, “why do species change over time?”, “how do species interact with the environment and other species?”. To answer that kind of questions, I have gained abilities in phylogenetics, phylogeography, population genetics, plant systematics, botany, taxonomy, and population ecology. If these prior skills are useful for your research, or if you want to start something completely new, I am always available to work together with you. よろしくおねがいします！
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2022-04-18
お知らせ
“科学”からの招待状『質量とは何か この宇宙に存在する物質の根本的性質とその起源を考える』放送大学（BS 231ch）にて4月24日（日）より放送！
「質量」という物理の基礎概念に焦点をあて、その理解の歴史的変遷について学ぶ4回シリーズが放送大学（BS 231ch）にて4月24日（日）より放送開始します。 初田 哲男（iTHEMS プログラムディレクター）、矢崎 紘一（iTHEMS 研究嘱託）、ゴードン・ベイム（iTHEMS 客員主管研究員）が「第4回これで物質の質量の起源はわかったか？」に出演します。放送は5月15日(日) 20:15～、6月26日(日) 8:15～（再）の予定です。 詳細は関連リンクをご覧ください。
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2022-04-18
今週の注目人物
Self-introduction: Yuto Moriwaki
Quantum field theory is a physical theory that describes a wide range of phenomena from the subatomic world to the cosmic scale, and can be regarded as a fruit of human wisdom. However, quantum field theory has not yet been mathematically formulated. This problem perhaps asks us, "How do we formulate space?" According to the philosophy of algebraic geometry, "space and algebra" are almost the same thing. Here, the algebra is a collection of functions (classical fields). So let us consider the algebra consisting of quantum fields. The "classical algebra" is associative, whereas the "quantum algebra" is non-associative. What should be the corresponding space? I am currently studying this algebra of quantum fields in the case of two-dimensional quantum field theory. In my previous research, I have worked mathematically on (1) a formulation of the algebra of two-dimensional conformal field theory, (2) constructions of examples, and (3) a construction of non-perturbative deformations. More recently, I have returned to the question of "space" a bit, studying the axioms (consistency) of quantum field theory from a viewpoint of an operad structure of moduli spaces and higher categories. I was originally a pure mathematician studying representation theory. Crossing the field into physics has been fruitful for my life, although there is still a lot I don't understand. I am very happy to be here at iTHEMS and hope to have good interactions and co-evolution with many researchers.
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2022-04-15
今週の注目人物
Self-introduction: Shou Yoshikawa
My name is Shou Yoshikawa. I joined RIKEN iTHEMS as an SPDR in April 2022. I am a mathematician studying algebraic geometry. I am interested in an analog of the existence of Kähler-Einstein metric to positive characteristic. Algebraic geometry in positive characteristic is a purely mathematical subject, however, the Einstein metric is deeply related to Physics. I hope that we find a new relation between mathematics and other sciences studying such analogies.
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2022-04-15
今週の注目人物
Self-introduction: Daiki Kumakura
My name is Daiki Kumakura. I joined iTHEMS as JRA (Junior Research Associate) in April 2022. My research fields are microbial evolutionary ecology and mathematical biology. Still undergraduate, I researched the metabolism of deep marine microbes with transcriptome analysis and comparative genome analysis. Because I am interested in the evolutionary process of microbes with the ecological interactions, I currently have researched the coevolution of microbes with theoretical analysis. Then, I do interdisciplinary research of fieldwork and theoretical simulation. The main field is a hot spring (Japanese is an onsen). I sample the sediments and water at each location and do bioinformatics. In the theoretical analysis, I construct mathematical modeling and simulation. I have the unique experience of discussing with theoretical researchers in various fields at iTHEMS. Through this interdisciplinary research and discussion, I hope to make my doctoral course meaningful.
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2022-04-15
今週の注目人物
Self-introduction: Taketo Sano
My name is Taketo Sano. I joined iTHEMS as a special postdoctoral researcher in April 2022 after I got the Ph.D. in mathematical sciences from the University of Tokyo. My research area is in low-dimensional topology and knot theory. I am interested in the intersection of (or interaction between) topology and combinatorics. Spaces are inherently infinite and beyond direct computations, while their algebraic images (under some nice mappings) are usually more tractable, and in some cases algorithmically computable. When one finds nice properties in the algebraic level, it is natural to expect that they are reflections of some hidden structures in the spacial level. My aim is to investigate the nature of the unseeable spaces through their algebraic images, by using theoretical tools (from algebraic topology, homotopy theory and category theory) together with computer powers.
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2022-04-14
今週の論文Week 3, April 2022
Title: The closest lineage of Archaeplastida is revealed by phylogenomics analyses that include Microheliella maris Author: Euki Yazaki, Akinori Yabuki, Ayaka Imaizumi, Keitaro Kume, Tetsuo Hashimoto, Yuji Inagaki Journal Reference: Open Biology 12: 210376 (2022) doi: https://doi.org/10.1098/rsob.210376 Title: Quantum Simulation for High Energy Physics Author: Christian W. Bauer. Zohreh Davoudi, A. Baha Balantekin, Tanmoy Bhattacharya, Marcela Carena, Wibe A. de Jong, Patrick Draper, Aida El-Khadra, Nate Gemelke, Masanori Hanada, Dmitri Kharzeev, Henry Lamm, Ying-Ying Li, Junyu Liu, Mikhail Lukin, Yannick Meurice, Christopher Monroe, Benjamin Nachman, Guido Pagano, John Preskill, Enrico Rinaldi, Alessandro Roggero, David I. Santiago, Martin J. Savage, Irfan Siddiqi, George Siopsis, David Van Zanten, Nathan Wiebe, Yukari Yamauchi, Kübra Yeter-Aydeniz, Silvia Zorzetti arXiv: http://arxiv.org/abs/2204.03381v1 Title: Goussarov-Polyak-Viro Conjecture for degree three case Author: Noboru Ito, Yuka Kotorii, Masashi Takamura arXiv: http://arxiv.org/abs/1905.01418v3
131件のニュース / 2022年