ニュース
208件のニュース / 2022年

20220901
今週の論文Week 1, September 2022
Title: Impact of Neutrino Cooling on TypeI Xray Bursts and Xray Superbursts Author: Akira Dohi, Nobuya Nishimura, Hajime Sotani, Tsuneo Noda, Helei Liu, Shigehiro Nagataki, Masaaki Hashimoto arXiv: http://arxiv.org/abs/2208.14622v1 Title: Functional Renormalization Group Approach to Circuit Quantum Electrodynamics Author: Takeru Yokota, Kanta Masuki, Yuto Ashida arXiv: http://arxiv.org/abs/2208.14107v1 Title: Binarycoupling sparse SYK: an improved model of quantum chaos and holography Author: Masaki Tezuka, Onur Oktay, Enrico Rinaldi, Masanori Hanada, Franco Nori arXiv: http://arxiv.org/abs/2208.12098v1

20220830
ホットトピックFeatured articles on iTHEMS published in "Sugaku Tsushin"
iTHEMS was featured in the August volume of "Sugaku Tsushin" (Japanese magazine published by The Mathematical Society of Japan). Our colleagues, Tetsuo Hatsuda, Ade Irma Suriajaya, Yosuke Kubota, Hiroyasu Miyazaki and Yukimi Goto, have written essays on iTHEMS in the volume. Let's see mathematicians' thoughts on the iTHEMS atmosphere.

20220829
プレスリリース新型コロナウイルス感染者の隔離短縮は可能か？－隔離終了タイミング検証のシミュレータを開発－
国立大学法人東海国立大学機構 名古屋大学大学院理学研究科の岩見真吾教授（兼理化学研究所数理創造プログラム客員研究員）は、米国インディアナ大学の江島啓介助教らとの共同研究で、抗原検査により新型コロナウイルス（COVID19）感染者の隔離を終了するタイミングを検証するためのシミュレータ（シミュレーションのためのソフトウエア）を新たに開発しました。 これにより、決められた回数の抗原検査の陰性結果をもって、早期にCOVID19感染者の隔離を終了できる、柔軟で安全な隔離戦略が提案できるようになります。 感染者隔離は感染拡大を防ぐ重要な手段です。長期にわたる隔離は二次感染のリスクを下げる一方で、隔離される人やそれを支える社会も様々な負担を被ります。 研究グループは、開発したシミュレータを用いて、"感染性のある患者の隔離を（早く）終了してしまうリスク"と"感染性を失った患者を不要に隔離してしまう期間（隔離に関わる負担）"の計算に成功しました。この結果、リスクと負担を同時に抑えるための個人差を考慮した適切な隔離戦略を、抗原検査を用いて実施する方法を提案できるようになりました。感染予防対策を徹底しつつ社会活動を再開・維持するウィズコロナの時代を迎えるにあたり、抗原検査をうまく利用することで教育活動や社会活動を安全に実施することができるようになります。 現在、臨床・疫学データや経験則に基づいた異なる隔離基準が国ごとに採用されている状況に対して、本研究は、数理モデルに基づいた、日本のみならず世界的に求められている柔軟な隔離ガイドラインの確立に貢献できると期待されます。 詳細は関連リンクより名古屋大学 研究成果発信サイトをご覧ください。

20220826
セミナーレポートABBLiTHEMS Joint Astro Seminar by Dr. Yosuke Mizuno on August 26, 2022
Dr. Yosuke Mizuno presented the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength 1.3 mm. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of ~50 microarcsecond. Using a large suite of numerical simulations, The EHT group demonstrated that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ∼4 million solar mass, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser propermotion studies. Their model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50 deg), as well as nonspinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way. In the seminar, Dr. Yosuke Mizuno focused on more theoretical interpretation and model comparison to understand the accretion flow properties nearby Sgr A*. Reported by Shigehiro Nagataki

20220826
リサーチニュースRIKEN Research: Applying quantum speed limits to macroscopic systems
An expression for the maximum speed at which changes in macroscopic systems can occur has been derived by a theoretical physicist at RIKEN. This will deepen our understanding of quantum phenomena in systems that are not in equilibrium. One of the hardest aspects of quantum mechanics to grasp is the Heisenberg uncertainty principle that states that it is not possible to simultaneously pin down both the position and momentum of an object. In other words, the more precisely a particle’s position is determined, the broader the range of its possible momentum becomes (and vice versa). In 1945, two physicists, Leonid Mandelstam and Igor Tamm, focused on another type of the uncertainty relation, namely one between time and energy fluctuation, and showed that transitions in quantum systems don’t happen instantaneously; rather, the speed at which a transition occurs is capped by an amount determined by how much the energy of the system fluctuates. Many other socalled quantum speed limits have subsequently been derived, which have helped better understand the physics of quantum systems and have been useful in various quantum applications. But big problems arise when quantum speed limits are applied to macroscopic systems. “Previous quantum speed limits, which are useful for small systems, typically become meaningless for macroscopic transitions,” notes Ryusuke Hamazaki of the Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team. “For example, conventional quantum speed limits give an infinite upper bound for the speed of transitions in a gas made up of atoms.” To read more, please visit the related link.

20220825
今週の論文Week 4, August 2022
Title: Highenergy neutrinos and gamma rays from winds and tori in active galactic nuclei Author: Susumu Inoue, Matteo Cerruti, Kohta Murase, RuoYu Liu arXiv: http://arxiv.org/abs/2207.02097v2 Title: ALMA detection of parsecscale blobs at the head of kiloparsecscale jet in the nearby Seyfert galaxy NGC 1068 Author: Tomonari Michiyama, Yoshiyuki Inoue, Akihiro Doi, Dmitry Khangulyan arXiv: http://arxiv.org/abs/2208.08533v1

20220822
ホットトピック大分STEMフェスタが大分市で開催されました
2022年7月23日に大分STEMフェスタが大分市で開催され、iTHEMSから初田哲男ディレクターが参加し、（株）ADKと協力して、Bコース「ブラックホール・レコーダーで1000年後にメッセージを届けよう」において、５０名を越える大分県各地から集まった高校生にブラックホールの解説と、Useless Prototyping Studioで制作したブラックホールレコーダーの実演を行いました。 また、情報ストレージとしてのブラックホールに、未来に託す俳句を記録する内容を高校生同士で話し合い、最近撮像されたブラックホール写真に書き込んでもらいました。 大分STEMフェスタには１５０名を越える高校生が参加し、Aコース「月面ローバー体験をしよう！」、Bコース「ブラックホール・レコーダーで1000年後にメッセージを届けよう」、Cコース「VR技術×社会の課題解決×SDGs」、Dコース「大分の未来に必要な仕事を考えよう」に分かれて、たいへん有意義な一日を過ごしました。iTHEMSからは、初田プログラムディレクターに加えて、アシスタントの和田ひとみさんと太田千賀子さんが現地でBコース開催に貢献されました。

20220818
受賞情報The paper by Dr. T. Hayata, Dr. Y. Hidaka and others has been selected as "Editors' Choice" of Progress of Theoretical and Experimental Physics
The Physical Society of Japan has announced that the paper entitled "Lattice Lindblad simulation" by Dr. Tomoya Hayata Itou (iTHEMS Visiting Scientist/Keio Univ.), Dr. Yoshimasa Hidaka (iTHEMS Visiting Scientist/KEK) and their collaborator has been selected as the Editors' Choice in Progress of Theoretical and Experimental Physics.

20220818
ホットトピック瀧雅人氏著「これならわかる深層学習入門」が大槻東已氏によって日本物理学会誌のコラムで紹介されました
瀧雅人氏（iTHEMS客員研究員/立教大学)がiTHEMS在籍中に執筆された著書「これならわかる深層学習入門」が、日本物理学会誌（2022年8月号）のコラム“ラ・トッカータ“で、大槻東已氏（上智大学）により取り上げられています。この教科書の特徴として、1. 物理をバックグラウンドにした読者がつまずくところをわかっている、2. 例が簡単すぎず自明すぎず、例をよむことでわかった気になる、3. 分量が適度、 4. 各節が細かく区切られているのでゼミに最適、5. 付録も勉強になる。など絶賛 。深層学習を１から学びたい方、ゼミで輪講したい方にお薦めです。

20220811
今週の論文Week 2, August 2022
Title: Calibration of nuclear charge density distribution by backpropagation neural networks Author: ZuXing Yang, XiaoHua Fan, Tomoya Naito, ZhongMing Niu, ZhiPan Li, Haozhao Liang arXiv: http://arxiv.org/abs/2205.15649v2 Title: Stability against threebody clustering in onedimensional spinless pwave fermions Author: Yixin Guo, Hiroyuki Tajima arXiv: http://arxiv.org/abs/2208.03654v1 Title: Thermal Ringdown of a Kerr Black Hole: Overtone Excitation, FermiDirac Statistics and Holography Author: Naritaka Oshita arXiv: http://arxiv.org/abs/2208.02923v1 Title: Tricritical phenomena in holographic chiral phase transitions Author: Masataka Matsumoto arXiv: http://arxiv.org/abs/2208.02605v1

20220808
ホットトピックiTHEMS Science Outreach Workshop 2022 was held on July 2931, 2022
On July 2931, we had Meeting on Outreach of RIKEN iTHEMS 2022 @Kobe & Zoom. This year the meeting was hosted by Suuri Cool Kobe and the venue was the auditorium (8F) + the cafeteria (6F) of Kobe Integrated Innovation Building (IIB). This meeting was hit by the big growth of infected population by Covid19 omicron BA.5. However, under careful preparation and precaution taken, 27 people participated at Kobe IIB and 24 more by zoom. There were 11 talks at the venue and 6 talks by zoom. 4 talks were by members of iTHEMS explaining recent development in various fields in sciences. 3 talkes were from universities on different aspects of research or fostering young researchers. 10 talks were given by journalists. There were also 3 posters (2 on research and 1 on a monthly academic magazine), in addition, the Black Hole Reacorder was exhibited at the cafeteria. The participants consist of 9+10 members from RIKEN, 6+4 from universities and 12+10 journalists (at venue + by zoom). By the success of this meeting, we hope the continuation of Journalist in residence program and this workshop next year.

20220808
セミナーレポートiTHEMS Math Seminar by Prof. Narutaka Ozawa on August 2, 2022
On August 2, Professor Narutaka Ozawa (RIMS, Kyoto University) gave a talk entitled "Product Replacement Algorithm, Semidefinite Programming, and Operator Algebras" in the iTHEMS Math Seminar. He elegantly explained how his recent study on Kazhdan's property (T) ties the field of functional analysis/operator algebras and that of computer sciences. Reported by Michiya Mori

20220805
セミナーレポートiTHEMS Math Seminar by Dr. Hokuto Konno on July 15, 2022
On July 15, there was a math seminar by Professor Konno. He gave an introductory talk on the SeibergWitten Floer homotopy type. Reported by Keita Mikami

20220804
今週の論文Week 1, August 2022
Title: Stochastic failure of cell infection post viral entry: Implications for infection outcomes and antiviral therapy Author: Christian Quirouette, Daniel Cresta, Jizhou Li, Kathleen P. Wilkie, Haozhao Liang, Catherine A. A. Beauchemin arXiv: http://arxiv.org/abs/2208.00637v1 Title: Structurepreserving numerical methods for constrained gradient flows of planar closed curves with explicit tangential velocities Author: Tomoya Kemmochi, Yuto Miyatake, Koya Sakakibara arXiv: http://arxiv.org/abs/2208.00675v1 Title: The ecoevolutionary dynamics of prior selfing rates promote coexistence without niche partitioning under conditions of reproductive interference Author: Koki R. Katsuhara, Yuuya Tachiki, Ryosuke Iritani, Atushi Ushimaru Journal Reference: Journal of Ecology, Volume109, Issue11, p.39163928 (2021) doi: https://doi.org/10.1111/13652745.13768 Title: Partitioning the temporal changes in abundancebased beta diversity into loss and gain components Author: Shinichi Tatsumi, Ryosuke Iritani, Marc W. Cadotte Journal Reference: Methods in Ecology and Evolution (2022) doi: https://doi.org/10.1111/2041210X.13921 Title: Black Hole as a Bound State of Semiclassical Degrees of Freedom Author: Yuki Yokokura arXiv: http://arxiv.org/abs/2207.14274v1

20220804
セミナーレポートSeminar by Dr. Xavier RocaMaza on August 3, 2022
As a part of the RCNP domestic workshop on lowenergy nuclear physics and highenergy astrophysics (RCNP研究会「低エネルギー核物理と高エネルギー天文学で読み解く中性子星」), the special seminar entitled "How does subatomic matter organize itself? A lowenergy nuclear physics perspective" was given by Prof. Xavier RocaMaza in U. Milan. This seminar is supported by Gravitational Wave and Equation of State Working Group (GWEOS WG), RIKEN iTHEMS Program. The equation of state (EoS) of nuclear matter is one of the essential things in nuclear physics. There have been many attempts to determine parameters characterizing the EoS experimentally, which have become paid attention more. He introduced various attempts and theoretical mechanisms, including cuttingedge proposals. More than 80 participants attended the seminar, including from the foreign country. Reported by Tomoya Naito

20220729
セミナーレポートiTHEMS Colloquium by Prof. Yasunori Nomura on July 26, 2022
Prof. Yasunori Nomura, the director of the Berkeley Center for Theoretical Physics, the University of California, Berkeley, visited iTHEMS and gave a colloquium entitled “From the Black Hole Conundrum to the Structure of Quantum Gravity” on July 26th. Prof. Nomura started the colloquium by explaining that the two pillars of modern physics, quantum mechanics and general relativity are actually at odds with each other, but each of them usually governs a different domain of physical phenomena, thus obscuring the incompatibility. The focus of the colloquium lies on one of the areas where both quantum mechanics and general relativity become equally important, namely quantum theory of black holes. Prof. Nomura illustrated how the famous phenomenon of black holes discovered by Stephen Hawking, Hawking radiation leads to socalled information paradox, in which the conservation the probability appears to be violated during the process of the radiation from the horizon. He went on to describe the key ingredients in solving the paradox, which are the concept of holography, the stretched horizon, and AdS/CFT correspondence. In the latter part of the colloquium, Prof. Nomura pedagogically showed the audience the most recent development in the study of the information paradox. The calculation including the contribution from “wormholes” was shown to reproduce the Page curve implying the recovery of the lost probability. The same calculation was also explained through formalism which was developed by Prof. Nomura himself. He concluded with the message that the study of the black hole conundrum is thus revealing the structure of quantum gravity, which involves with a wide range of various research fields such as high energy physics and astrophysics, quantum information science, and manybody physics. The colloquium was taken place at the 2F Large Meeting Room of RIBF Building and was attended by a limited number of audience in person due to the wide spreading of COVID19, but more than eighty people joined through zoom. Reported by Tsukasa Tada

20220728
今週の論文Week 5, July 2022
Title: Ceratozamia schiblii (Zamiaceae): A new cycad species from the eastern mountains of Oaxaca, Mexico Author: Miguel Angel PérezFarrera, José Said GutiérrezOrtega, Timothy J. Gregory, Jeffrey Chemnick, Silvia SalasMorales, Michael Calonje, Pedro DíazJiménez Journal Reference: Taxonomy 2(3):324338 (2022) doi: https://doi.org/10.3390/taxonomy2030025 Title: New developments in relativistic magnetohydrodynamics Author: Koichi Hattori, Masaru Hongo, XuGuang Huang arXiv: http://arxiv.org/abs/2207.12794v1

20220726
ホットトピックiTHEMS and RIKENBerkeley Center is featured in RIKEN at a Glance 2022
RIKEN's pamphlet "RIKEN at a Glance 2022" features iTHEMS and the newly opened RIKENBerkeley Center. Please see the related link for details.

20220725
セミナーレポートiTHEMS Biology Seminar by Dr. Namiko Mitarai on July 7, 2022
Dr. Namiko Mitarai (Niels Bohr Institute) gave us an amazing talk in the biology seminar. She told us about the collaborative works with experimental biologists on a microbial world. Some viruses that infect bacteria are known to provide immunity to infection by the same virus. According to her, noimmune bacteria can be protected from infection when the ratio of immune bacteria is substantially high in the population, which reminds us of our current cases for Covid19. Interestingly, the metabolic state of host (bacteria) also affects the virus infection. The talk was very very exciting. In the end of her seminar, she also showed us the tips for the successful collaboration with experimental biologists: (1) We (theorists) should care about them. (2) They (experimental biologists) should care about us. During and after the talk, there were lively discussion between the speaker and iTHEMS researchers. Thanks Mitaraisan!! Reported by Gen Kurosawa

20220721
リサーチニュースRIKEN NEWS: 原子も群れをつくって集団行動
ムクドリやイワシの大群が一斉に方向転換をするなど秩序だった集団行動をする姿は神秘的です。同様の現象は私たちの細胞など、より小さな世界でも確認されています。そして、さらに小さな原子の世界でも引き起こせることを、コンピュータによるシミュレーションで理論的に確認したという足立景亮基礎科学特別研究員（以下、研究員）に話を聞きました。 続きは関連リンクをご覧ください。

20220721
今週の論文Week 4, July 2022
Title: Stransformations for CFT$_2$ as linear mappings from closed to open sector linear spaces Author: Xun Liu arXiv: http://arxiv.org/abs/2207.08480v1

20220715
セミナーレポートiTHEMS Biology Seminar by Dr. Junnosuke Teramae on July 14, 2022
In this week’s biology seminar, we were very happy to have Dr. Junnosuke Teramae from Kyoto University to tell us about the mysterious stochastic behavior of neurons and synapses in the brain. Many biological experimental observations are reported. However, how this stochasticity is beneficial for computation and learning in the brain remains largely unknown. Dr. Teramae presented his work on developing an efficient learning algorithm inspired by this brain behavior. The algorithm is based on Gibbssampling which allow us to efficiently obtain highdimensional sampling results. The algorithm shows similar stochastic behavior of the brain, which other machine leaning algorithms doesn’t show. In the end, Dr. Teramae briefly showed us the algorithm enables us to reproduce the recently discovered efficient powerlaw coding in the cortex. Even the seminar time is ended, the discussion continued for a long while. The seminar inspired many open questions on brain behavior and learning algorithms, both for the speaker and the audiences. We look forward to further development on the subjects. We thank Dr. Junnosuke Teramae and everyone joined the seminar. Reported by Yingying Xu

20220715
セミナーレポートQuantum Matter Seminar by Dr. Ken Shiozaki on July 12, 2022
Prof. Ken Shiozaki gave a seminar about adiabatic cycles of quantum spin systems. Topological phases of matter without ground state degeneracy are known as inevitable phases. In the literature, their topological properties have been wellstudied in freefermion and manybody systems. The speaker started with the transversefield Ising model and the RiceMele model to demonstrate the pumping of the 1D chain in an adiabatic cycle. He then generalized the concept to cover broader systems, including general spatial dimensions and generic models with any onsite symmetry, such as timereversal, Z2 Ising, and U(1). He demonstrated that one can classify adiabatic cycles of a spin model, which can be characterized by a Z2 topological invariant. This talk showed that symmetryprotected topological phases emerge by performing an adiabatic cycle. Reported by ChenHsuan Hsu (YITP, Kyoto University)

20220714
今週の論文Week 3, July 2022
Title: Spatially resolved study of the SS 433/W50 west region with Chandra: Xray structure and spectral variation of nonthermal emission Author: Kazuho Kayama, Takaaki Tanaka, Hiroyuki Uchida, Takeshi Go Tsuru, Takahiro Sudoh, Yoshiyuki Inoue, Dmitry Khangulyan, Naomi Tsuji, Hiroaki Yamamoto arXiv: http://arxiv.org/abs/2207.05924v1 Title: Constraining primordial curvature perturbations using dark matter substructure Author: Shin'ichiro Ando, Nagisa Hiroshima, Koji Ishiwata arXiv: http://arxiv.org/abs/2207.05747v1 Title: QFT approach to dressed particle processes in preheating and nonperturbative mechanism in kinematicallyforbidden regime Author: Hidetoshi Taya, Yusuke Yamada arXiv: http://arxiv.org/abs/2207.03831v1

20220713
セミナーレポートiTHEMS Theoretical Physics Seminar by Prof. Hiroshi Suzuki on July 5, 2022
The iTHEMSphys intensive lecture was held on July 5 and 6, 2022. The speaker is Prof. Hiroshi Suzuki at Kyushu University. The title is “Gradient flow exact renormalization group.” Wilson’s exact renormalization group (ERG), which tells how a system changes under the scale transformation, provides a fundamental framework to define quantum field theory even beyond the perturbation theory. It has, however, been known that it is difficult to preserve a manifest gauge symmetry in ERG because of the usage of the momentum cutoff in ERG. Recently, he has proposed a possible modification of ERG, the gradient flow exact renormalization (GFERG), which preserves a manifest gauge symmetry being based on a gaugecovariant diffusion equation. He has explained the basic idea and properties of GFERG. He has also presented a possible application of GFERG to the consideration of the axial anomaly. The lecture was held via Zoom. There were about 30 participants from iTHEMS and other universities. The participants enjoyed fruitful discussions throughout the lecture. Reported by Kengo Kikuchi

20220707
今週の論文Week 2, July 2022
Title: Nuclear ManyBody Effect on Particle Emissions Following Muon Capture on $^{28}$Si and $^{40}$Ca Author: Futoshi Minato, Tomoya Naito, Osamu Iwamoto arXiv: http://arxiv.org/abs/2207.02514v1 Title: A symmetry principle for gauge theories with fractons Author: Yuji Hirono, Minyoung You, Stephen Angus, Gil Young Cho arXiv: http://arxiv.org/abs/2207.00854v1 Title: Velocity of Sound beyond the HighDensity Relativistic Limit from Lattice Simulation of Dense TwoColor QCD Author: Kei Iida, Etsuko Itou arXiv: http://arxiv.org/abs/2207.01253v1 Title: A note on generalized ThurstonBennequin inequalities Author: Nobuo Iida, Hokuto Konno, Masaki Taniguchi arXiv: http://arxiv.org/abs/2207.00229v1

20220706
セミナーレポートiTHEMS Biology Seminar by Mr. Keiichi Morita on June 23, 2022
I talk about how evolution of sexual traits such as ornaments of guppies can affect coexistence of two closely related species. First, I introduce "reproductive interference," sexual interaction driving evolution of sexual traits. Second, I show how to formulate population dynamics of two closely related species with reproductive interference. Next, I introduce mathematical modeling of quantitative genetics in order to formulate trait evolution. Finally, I show results of analysis and simulation by combining population dynamics and evolution (i.e., ecoevolutionary feedbacks). In future works, I should the effect of costs of evolution or the other species. Thank you for your listening and giving me comments! Reported by Keiichi Morita

20220705
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 multipulse spectroscopy, and applied these ideas to 1D topological superconductors. Reported by Thore Posske (University of Hamburg) and ChingKai Chiu

20220704
セミナーレポートABBLiTHEMS Joint Astro Seminar by Mr. Tomoki Matsuoka on July 1, 2022
Mr. Tomoki Matsuoka gave an excellent talk on the longterm 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 corecollapse 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 ultrastripped supernova remnant (USSNR), which originated from a corecollapse SN explosion proposed to be a candidate formation site of a double neutron star binary. By accounting for the massloss history of the progenitor binary using a model developed by a previous study, he constructed the largescale 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

20220704
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

20220704
今週の注目人物Selfintroduction: 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 HeriotWatt 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.

20220630
今週の論文Week 5, June 2022
Title: Role of the effective range in the densityinduced BECBCS crossover Author: Hiroyuki Tajima, Haozhao Liang arXiv: http://arxiv.org/abs/2206.12599v1

20220628
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 longterm 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.

20220628
リサーチニュースRIKEN Research: Worming out of the blackhole 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.

20220627
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

20220623
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 nonHermitian topological phases. The seminar started with a succinct introduction to nonHermitian 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 HatanoNelson 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 nonHermitian 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 higherdimensional systems or to other nonHermitian systems with Z2 topological invariants. Reported by ChenHsuan Hsu (YITP) and ChingKai Chiu

20220621
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 selforganization 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

20220620
セミナーレポートMathPhys 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 nonsingular 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

20220616
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

20220609
セミナーレポートiTHEMS Biology Seminar by Dr. José Said GutiérrezOrtega 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 highlatitude 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 highlatitude 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 latitudeassociated 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 GutiérrezOrtega

20220609
今週の論文Week 2, June 2022
Title: Ordered and tunable Majoranazeromode lattice in naturally strained LiFeAs Author: Meng Li, Geng Li, Lu Cao, Xingtai Zhou, Xiancheng Wang, Changqing Jin, ChingKai Chiu, Stephen J. Pennycook, Ziqiang Wang, HongJun Gao Journal Reference: Nature (2022) doi: https://doi.org/10.1038/s41586022047448 Title: Observing Supernova Neutrino Light Curves with SuperKamiokande. 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 ManyBody Localization Author: Ryusuke Hamazaki, Masaya Nakagawa, Taiki Haga, Masahito Ueda arXiv: http://arxiv.org/abs/2206.02984v1 Title: Semiclassical Gravity from Averaged Boundaries in twodimensional BCFTs Author: Yuya Kusuki arXiv: http://arxiv.org/abs/2206.03035v1 Title: Evaluations of uncertainties in simulations of propagation of ultrahighenergy cosmicray 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 RadiationHydrodynamics 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: Semianalytical 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

20220609
ホットトピックRIKENBerkeley Center was opened
RIKEN iTHEMS and N3AS Physics Frontier Center have started a joint research center, RIKENBerkeley 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 2729, 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.

20220609
今週の注目人物Selfintroduction: 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 nonperturbative 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 socalled 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.

20220608
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 matterantimatter 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 Xray 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 matterantimatter 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 freezein, then freezeout, 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 welldeveloped. We will see indicative predictions in the near future! Neutrino physics will open new windows for our Universe! Reported by Nagisa Hiroshima

20220608
セミナーレポートABBLiTHEMS Joint Astro Seminar by Dr. Kanji Mori on June 3, 2022
Axionlike particles (ALPs) are a class of hypothetical bosons that feebly interact with ordinary matter. The hot plasma of stars and corecollapse 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 corecollapse 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 40400 MeV. Reported by Shigehiro Nagataki

20220608
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!

20220606
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 selfreliance. 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!

20220606
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。

20220602
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 rprocess 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 KobayashiWarrenCarter 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

20220530
セミナーレポートMathPhys Seminar by Dr. Toshifumi Noumi on May 19, 2022
Dr. Toshifumi Noumi (Kobe University) gave a pedagogical seminar on the socalled 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
208件のニュース / 2022年