News
175 news in 2022

20220406
Person of the WeekSelfintroduction: Tomoya Naito
My name is Tomoya Naito. I joined RIKEN iTHEMS as an SPDR in April 2022, while I have participated in many activities in iTHEMS including the iTHEMSphys study group and the iTHEMS mathphys working group so, probably, some of you have known me. My research topics are related to computational quantum manybody problems, especially density functional theory (DFT). In principle, one can obtain all the properties of quantum manybody problems by solving the manybody Schrödinger or Dirac equation; however, it is, in practice, difficult to solve it. DFT, developed by Hohenberg, Kohn, and Sham, is one of the efficient methods to solve such problems. DFT has been applied to the study of atomic nuclei, atoms, molecules, and solids for decades, while there are still many fundamental things to be solved or understood. My research topics are briefly divided into two parts: fundamental studies of the DFT and studies of quantum manybody problems (atomic nuclei, atoms, molecules, and solids) using DFT. Recently, I have started an astrophysical study using knowledge of nuclear physics and a study of the mathematical aspect of DFT in collaboration with iTHEMS (previous or current) members. I look forward to extending collaborations with iTHEMS colleagues!

20220406
Research NewsRIKEN Research: Thermal electrons play key role in determining emissions from gammarayburst afterglows
he presence of unusually energetic gamma rays seen in some afterglows from intense gammaray bursts (GRBs) could be explained by a new mathematical model developed by RIKEN researchers1. This finding could help to shed light on the origin of GRBs. A GRB is a spectacular eruption of energy produced by violent events such as the explosive death of a massive star, or the collision of two neutron stars. A GRB also shoots a jet of matter and energy into the material that surrounded the star, shocking particles such as protons and electrons and causing them to emit radiation. The emitted photons, ranging from radio waves to gamma rays, can be detected from Earth as a GRB afterglow. The vast majority of GRB afterglow observations can be explained by current theories, which should come as no surprise: they wouldn’t be the current theories if they didn’t match reality. But the afterglows of two recent GRBs produced gamma rays with unusually high energies that strain these theories. “The surprise with these two bursts was that we had never detected photons this energetic before,” says Donald Warren of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS). To read more, please visit the related link.

20220406
Person of the WeekSelfintroduction: Jizhou Li
My name is Jizhou (GJoe) Li. Born and raised in Beijing, got my PhD from the Washington State University, I’m now thrilled to join the RIKEN iTHEMS team as a postdoc researcher. A theoretical physicist by training, I have worked on nonlinear dynamical systems and quantum chaos during my PhD and postdoc years. After joining the RIKEN in April 2022, I will embark on a new journey in the field of computational virophysics to study the dissemination of viruses in various circumstances, as well as the interactions between the viruses and the hosts environments. Looking forward to expand my spectrum and learn from collaborators in different fields.

20220406
Person of the WeekSelfintroduction: Keiichi Morita
My name is Keiichi Morita, and I joined iTHEMS in April 2022 as a junior research associate / student trainee. I am now involved in a Ph.D. program at the SOKENDAI University. The main question of my research is how adaptive evolution can determine species coexistence and structures of ecological communities. I focus on rapid adaptation which can change the strength and directions of species interactions and finally affect population dynamics. I hope to understand how the evolution of an individual phenotype can affect species coexistence by formulating transient processes and finding conditions of coexistence from analysing and simulating my mathematical models. I consider analyzing experimental data and demonstrating my mathematical models. My final goal is to discover a general rule in ecology. I am looking forward to interacting with other members working with various interests in iTHEMS and finding a new direction of research out of it.

20220401
Press ReleaseRIKEN iTHEMS, the University of Tokyo and Kyoto University Launch New InterUniversity Lecture Program Using Online Classes
The RIKEN (RIKEN) Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS), the College of Arts and Sciences of the University of Tokyo and the Faculty of Science of Kyoto University will launch a new interuniversity collaborative online lecture system in April 2022, offering courses on various aspects of mathematical sciences to students in both faculties. In addition to faculty members from the University of Tokyo and Kyoto University, young researchers from RIKEN and other research institutes will give a series of lectures, which students can take as courses at their respective universities and earn credits. This new lecture format allows students to learn the fundamentals and applications of mathematical science, which form the foundation of modern society, from frontline researchers as early as their undergraduate years. At the same time, it enables the development of young human resources beyond the boundaries of universities. Active discussions between young researchers and students in class are expected to lead not only to the development of basic scientific research, but also to the development of human resources who will create innovations in society in the future. For more information, please see the related link.

20220401
Seminar ReportiTHEMS Biology Seminar by Dr. Euki Yazaki on March 17, 2022
At the March 17th seminar , I presented my research. It was mainly an analysis of the phylogenetic position of orphan organisms (organisms whose phylogenetic position is unknown) based on largescale sequence data, and in addition, I showed that huge lineages (Archaeplastida), including plants, are monophyletic. Although monophyly of Archaeplastida has been debated for many years, this study clarified that they are monophyletic and why they were not monophyletic in previous research. The seminar was very active, with many questions about the methods of phylogenetic analysis and biological questions.

20220401
Person of the WeekSelfintroduction: Yan Lyu
I am a Ph. D candidate in Peking University, China, and I joined iTHEMS on April 1st 2022 as a student trainee. I am interested in understanding the interactions between hadrons from the fundamental theory, i.e., quantum chromodynamics (QCD). It is in some sense similar with determining the Coulomb interaction between two objects by calculating a simple integral using a pen and a piece of paper, like highschool students usually do in their physical class. However, as far as QCD is concerned, such an integral is too complicated to be done by using a pen and a piece of paper, thus I employ the socalled lattice QCD method to calculate such an integral by supercomputers. Once the interactions are determined from QCD, one can use them to various systems from nuclei to neutron star. I am very happy to join iTHEMS, and I look forward to interacting with people from various fields.

20220401
Person of the WeekSelfintroduction: Kotaro Murakami
My name is Kotaro Murakami and have joined iTHEMS since April 2022 as a student trainee. My research is to solve the mystery of hadrons from the firstprinciple calculation of quantum chromodynamics (QCD). QCD is a theory describing the dynamics of quarks and gluons, and hadrons are composed of these particles. There are several hadrons we do not know how are created from quarks and gluons, which are called exotic hadrons. My ultimate goal is to identify all of the hadrons including exotic hadrons from QCD. I am working on the lattice QCD studies of baryon resonances from mesonbaryon scatterings. I hope to have fruitful discussions in iTHEMS with not only people in particle physics or hadron physics but people in other fields.

20220401
Person of the WeekSelfintroduction: Xun Liu
My name is Xun Liu, and I joined iTHEMS in April 2022 as a student trainee. I am now involved in a PhD program at the University of Tokyo. My current research project and interest mainly lies in the field of twodimensional conformal field theory, string theory, and string field theory. I am also interested in the relationship of these fields with formal mathematical topics, including group and representation theory, and analytical geometry. I am looking forward to interacting with mathematicians to form a more mathematical welldeveloped language in describing CFT and string theory.

20220331
AwardDr. Miyazaki receives FY2021 RIKEN Excellent Achievement Award
Hiroyasu Miyazaki (Visiting Scientist, iTHEMS) received "FY2021 RIKEN Excellent Achievement Award (RIKEN BAIHO Award)" on March 23, 2022 for his achievement on "Development of generalized theory of motives". Congratulations !

20220331
Paper of the WeekWeek 5, March 2022
Title: Diffeomorphisms of 4manifolds with boundary and exotic embeddings Author: Nobuo Iida, Hokuto Konno, Anubhav Mukherjee, Masaki Taniguchi arXiv: http://arxiv.org/abs/2203.14878v1 Title: Femtoscopic study on $DD^*$ and $D\bar{D}^*$ interactions for $T_{cc}$ and $X(3872)$ Author: Yuki Kamiya, Tetsuo Hyodo, Akira Ohnishi arXiv: http://arxiv.org/abs/2203.13814v1

20220331
Press ReleaseChaos theory provides hints for controlling the weather
A research team led by Takemasa Miyoshi (Deputy Program Director, iTHEMS) has devised a new theory of control simulation experiments to study weather controllability. Under a project led by the RIKEN Center for Computational Science, researchers have used computer simulations to show that weather phenomena such as sudden downpours could potentially be modified by making small adjustments to certain variables in the weather system. They did this by taking advantage of a system known as a “butterfly attractor” in chaos theory, where a system can have one of two states—like the wings of a butterfly—and that it switches back and forth between the two states depending on small changes in certain conditions. To read more, please see the related link.

20220331
Hot TopiciTHEMS NOW & NEXT FY2021 was held on March 25, 2022
The annual inhouse gathering entitled iTHEMS NOW and NEXT FY2021 was held on March 25th online. The gathering is an occasion that we discuss the current status and future perspectives on our research and organization. The event started with five keynote talks given by Takeru Yokota, Yalong Cao, Ryosuke Iritani, Ryo Namba, Keita Mikami. After a short break a session on the proper practices in conducting scientific researches followed during lunch time. In the session, the participants discussed their research practices in small groups and later shared their discussions with all. In the afternoon, each working group and study group made their progress reports. Program Director Hatsuda’s remarks concluded the gathering.

20220330
Seminar ReportQuantum Matter Seminar by Dr. Tiantian Zhang on March 24, 2022
The Quantum Matter Study Group invited Dr. Tiantian Zhang from Tokyo Institute of Technology to talk about the local and global topology for Tgprotected Z_{2} Dirac points. In the beginning, by introducing the topological phase in the gapped and gapless systems, she discussed the conventional and Z_{2} Dirac points. Surprisingly, she established gaugeinvariant charge formula and bulksurface correspondence for Z_{2} Dirac points, which can give a full understanding about the topology of Tgprotected Z_{2} Dirac points. Then, she proposed the first Z_{2} Dirac material candidate Li2B4O7 for further exploration. Reported by Congcong Le

20220325
Event ScheduleEvents for the 5th week of March 2022
Wednesday, March 30, 13:30– 15:00 NEW WG Seminar Thursday, March 31, 10:00 11:00 iTHEMS Biology Seminar

20220325
Seminar ReportHow is mathematics utilized in society?  Exploring the Essence of Mathematical Research Special Lecture by Shigefumi Mori and Takashi Sakajo on March 12, 2022
On March 12, a zoom discussion by two mathematicians, Takashi Sakajyo (Kyoto U./iTHEMS) and Shigefumi Mori (KUIAS/iTHEMS), was held as an iTHEMS x academist special event "How is mathematics utilized in society?" More than 380 people from academia, schools, and companies have joined online. After the introductory talks on the usefulness of mathematics in modern times by Sakajyo san, and on the beauty and joy of mathematics by Mori san, they had interesting discussions on three topics, the relation between mathematics and society, mathematics education, and how do mathematicians face mathematical problems? Reported by Tetsuo Hatsuda

20220324
Paper of the WeekWeek 4, March 2022
Title: Quantum and classical annealing in a continuous space with multiple local minima Author: Yang Wei Koh, Hidetoshi Nishimori arXiv: http://arxiv.org/abs/2203.11417v1 Title: Dehn twists and the Nielsen realization problem for spin 4manifolds Author: Hokuto Konno arXiv: http://arxiv.org/abs/2203.11631v1 Title: Neutron star mass formula with nuclear saturation parameters Author: Hajime Sotani, Hajime Togashi Journal Reference: Phys. Rev. D 105(6), 063010 (3/2022) arXiv: http://arxiv.org/abs/2203.09004v1

20220322
Hot TopicFarewell message from Dr. Akinori Tanaka
Our colleague Akinori Tanaka moves on to a new carrier at RIKEN AIP as of April 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Akinori Tanaka: First of all, I would like to thank my colleagues, assistants, and all the people for sharing time in iTHEMS. I really enjoyed discussing and chatting, even though I spent a lot of time online. In fact, this is the 2nd time for me to leave here. When I started my research as a member of iTHES, not iTHEMS at that time, I was working on theoretical physics. But, in addition to my own research, I also enjoyed chatting with my colleagues and getting new concepts: machine learning and related topics, and it opened up my next career. As a result, I returned to iTHEMS as a machine learning researcher, as you know. It was very surprising for me that all the activities were really sophisticated compared to the ones in iTHES, and I was happy to participate in the activities in information theory study group, SSP workshop, and chatting after the coffee meeting. Now I leave this message as if this was farewell, but it's not. I will move to RIKEN AIP from this April as a senior research scientist, but hold a post in iTHEMS also. I would like to deepen my thoughts on machine learning from mathematical, biological, and physical perspectives, so I'm happy if all of you discuss/chat with me as I have so far, even after April.

20220322
Hot TopicFarewell message from Dr. Kanato Goto
Our colleague Kanato Goto moves on to a new carrier at Kyoto University as of April 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Kanato Goto: I am leaving iTHEMS to move to Yukawa Institute for Theoretical Physics at Kyoto University. I have been very happy to have had the opportunity to work with you all for the past three years. The experience of discussing with scientists from various fields at iTHEMS is invaluable for my research carrier. The first year I joined iTHEMS, I stayed in the U.S. Regrettably, the Corona disaster struck during my stay, and I was deprived of the opportunity to interact with you all in person, even after returning to Japan. I hope to visit iTHEMS in the near future and discuss you again. I cannot thank the assistants enough for their great help. Thanks to them, I could devote myself to my research without any inconvenience. Thank you very much, all the iTHEMS members! See you again soon!

20220322
Hot TopicFarewell message from Dr. Naomi Tsuji
Our colleague Naomi Tsuji moves on to a new carrier at Kanagawa University as of April 1st. We all will miss her and wish her the best of luck in her latest endeavor. Here is a message from Naomi Tsuji: Since I joined iTHEMS in April 2020, my research life at iTHEMS completely overlapped with the pandemic. At first, I found it difficult to get to know each other and communicate with the other iTHEMS members through online meeting systems, but gradually it became possible and comfortable to me. I have been working on mainly data analysis of Xray or gammaray observations from astrophysical objects at iTHEMS, a group of theorists. I was glad that some members showed their interest in my study, and it was so exciting and stimulating to discuss about it. I wish I could have more discussion with many of the iTHEMS members in person and hope those days will come in the near future. Until then, let us stay healthy and have good science!

20220322
Hot TopicFarewell message from Dr. Yukimi Goto
Our colleague Yukimi Goto moves on to a new carrier at Kyushu University as of April 1st. We all will miss her and wish her the best of luck in her latest endeavor. Here is a message from Yukimi Goto: It may not be obvious to those in other fields, but iTHEMS is a unique place for Japanese mathematicians. Japanese mathematicians do not have many opportunities to talk with researchers in fields other than their own. I am an applied mathematician, but I did not have a chance to talk casually with physicists at university. After coming to iTHEMS and talking with physicists and biologists, I found that they are very interested in and expect a lot from mathematics. When I talked about my research, they always tried to understand it and asked me what kind of problems we could solve in mathematics. I enjoyed discussing with them, and it motivated me to do research. Although it was only two years and I met most of them online, I am grateful that I had such a wonderful time with them.

20220322
Hot TopicFarewell message from Dr. Takashi Okada
Our colleague Takashi Okada moves on to a new carrier at Kyoto University as of April 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Takashi Okada: I joined iTHEMS in 2018. My main workplace was in Hallatschek group, UC Berkeley. I researched on biophysics & evolutionary dynamics and learned a lot of things there. I also enjoyed working with iTHEMS members on interdisciplinary projects. I believe that some projects were made possible only by collaboration with wonderful iTHEMS members. I really appreciate iTHEMS' support during my longterm stay in Berkeley. Thanks to iTHEMS support, I could focus on work without any problems during this pandemic. From this spring, I am moving to Mochizuki Lab (Kyoto Univ) as a ProgramSpecific Associate Professor. The scientific atmosphere of ITHEMS is so great, and I hope that I can continue to collaborate with great members in iTHEMS. Let's keep in touch!

20220322
Seminar ReportiTHEMS Math Seminar by Dr. Lin Li on March 18, 2022
In March 18, there was a seminar by Dr. Lin Li. He explained his theoretical research on the control of hurricane. The main difficulty is that the order of the energy of the so large that it is 10^{6} times larger than the energy we could use. To overcome this difficulty, he explained some ideas and his simulation on how his ideas will work. Reported by Keita Mikami

20220317
Paper of the WeekWeek 3, March 2022
Title: Universality of linear perturbations in SU($N$)natural inflation Author: Tomohiro Fujita, Kai Murai, Ryo Namba arXiv: http://arxiv.org/abs/2203.03977v1 Title: New constraints on the neutronstar mass and radius relation from the terrestrial nuclear experiments Author: Hajime Sotani, Nobuya Nishimura, Tomoya Naito arXiv: http://arxiv.org/abs/2203.05410v1 Title: Neutron star mass formula with nuclear saturation parameters Author: Hajime Sotani, Hajime Togashi Journal Reference: Phys. Rev. D 105(6), 063010 (3/2022) arXiv: http://arxiv.org/abs/2203.09004v1

20220317
Event ScheduleEvents for the 4th week of March 2022
Thursday, March 24, 17:00– 18:15 Quantum Matter Seminar Friday, March 25, 9:30 16:00 iTHEMS NOW & NEXT

20220315
Seminar ReportiTHEMS Math Seminar by Dr. Pengyu Liu on March 11, 2022
In March 11, there was a math seminar by Dr. Pengyu Liu from computational climate science research team. In the first part, he explained two extract rules to obtain Boolean function from the neural network. In the second part, he explained how we can apply results in the first part to predict human Dicer cleavage sites. Reported by Keita Mikami

20220315
Seminar ReportiTHEMS Math Seminar by Dr. Shigenori Nakatsuka on January 28, 2022
Dr. Shigenori Nakatsuka from Kavli IPMU gave us a talk on dualities in Wsuperalgebras. In the first half of the talk he reviewed some basic concepts of vertex superalgebras, in particular Wsuperalgebras, and the FeiginFrenkel duality, which states that the Walgebras in a certain class are isomorphic to the other Walgebras associated with the dual Lie algebras and the dual levels. In the latter half of the talk he introduced dualities beyond the FeiginFrenkel duality including his recent work with Creutzig, Genra, and Sato. One of the remarkable results is the proof of the FeiginSemikhatov conjecture, which gives a correspondence between the Walgebras associated with certain Lie algebras and the Wsuperalgebras associated with the corresponding Lie superalgebras. His talk was so stimulating that we could enjoy the mathematics of Walgebras. Reported by Mizuki Oikawa

20220311
BookMathematical Modeling for Genes to Collective Cell Dynamics
Editor: Tetsuji Tokohiro Language: English Covers both experimental results and mathematical models to analyze cellular dynamics. Includes basic introductions in each chapter for nonexperts in biology or mathematics. Clear and concise structure that helps readers’ understanding.

20220311
Seminar ReportiTHEMS  RCCS(FTRT) Joint Online Seminar by Prof. Gergely Fejos on February 18, 2022
On Feb.18, 2022, Dr. Gergely Fejos (Eotvos Lorand Univ., Hungary) gave a talk at the first iTHEMS  RCCS(FTRT) Joint Seminar. He reported a functional renormalization group study of the three dimensional GinzburgLandau potential for the chiral phase transition in three flavor quantum chromodynamics. The order of the phase transition in this system has long been thought to be firstorder, but his conclusions suggest the possibility of a secondorder phase transition. A lively discussion took place between the speakers and the audience on this interesting result. Reported by Tetsuo Hatsuda

20220310
Paper of the WeekWeek 2, March 2022
Title: Merger and postmerger of binary neutron stars with a quarkhadron crossover equation of state Author: YongJia Huang, Luca Baiotti, Toru Kojo, Kentaro Takami, Hajime Sotani, Hajime Togashi, Tetsuo Hatsuda, Shigehiro Nagataki, YiZhong Fan arXiv: http://arxiv.org/abs/2203.04528v1 Title: Tunable Dirac Semimetals with Higherorder Fermi Arcs in Kagome Lattices Pd$_3$Pb$_2$X$_2$ (X = S, Se) Author: Simin Nie, Jia Chen, Changming Yue, Congcong Le, Danwen Yuan, Wei Zhang, Hongming Weng arXiv: http://arxiv.org/abs/2203.03162v1 Title: Universality of linear perturbations in SU($N$)natural inflation Author: Tomohiro Fujita, Kai Murai, Ryo Namba arXiv: http://arxiv.org/abs/2203.03977v1 Title: New constraints on the neutronstar mass and radius relation from the terrestrial nuclear experiments Author: Hajime Sotani, Nobuya Nishimura, Tomoya Naito arXiv: http://arxiv.org/abs/2203.05410v1

20220310
Seminar ReportFundamentals Fest, mini Preevent on Science "Exploring and Bridging: The Potential of Basic Science" was held on March 10, 2022
An online event was held on March 10, 2022 on the theme of the relationship between basic science and society. Sasada san (Mathematician), Yamagiwa san (anthropologist) and Hatsuda san (physicist), moderated by Tsuboi san (artist), had lively discussions on what the "universality" means in natural and social sciences, and also the role of scientists as "catalysts" to link science and society. The video is available on youtube. Please see the related link.

20220310
Seminar ReportiTHEMS Biology Seminar by Prof. Atsushi Mochizuki on March 10, 2022
In this week’s biology seminar, with great honor, we have Prof. Mochizuki to give us an interesting talk on “Independent regulation of multiple checkpoints in cellcycle network systemBiological function originated in the law of localization”. He showed us how mathematical analysis about the complex cell cycle networks can provide knowledge on nontrivial behaviors in regularization systems. The transformation from complex cell cycle networks to structural sensitivity matrix is amazing. He and his collaborator found the “buffering structure” which are essential local characters as the origin of biological function. Furthermore, “buffering structure” can generally appear in chemical reaction network including complex formation. He specially studied the G1S and G2M checkpoints in cell cycle. The analyses clarified that, even the two checkpoints are regulated by different protein complexes (Cdc2Cdc13 and Cdc2Cig2, respectively) with common species of proteins and activation reactions conform a complicated network, these two complexes are regulated by disjoint sets of reaction parameters in the system. We are looking forward to the further study of comparison with cell cycle experimental data. Many questions and discussions arose from the audiences. We appreciated very much the time Prof.Mochizuki shared with us. Reported by Yingying Xu

20220309
AwardThe paper by Dr. Etsuko Itou 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 "Negative string tension of a highercharge Schwinger model via digital quantum simulation" by Dr. Etsuko Itou (Postdoctoral Researcher, iTHEMS) and her collaborators has been selected as the Editors' Choice in Progress of Theoretical and Experimental Physics.

20220309
Seminar ReportiTHEMS Biology Seminar by Dr. Shingo Gibo on February 17, 2022
Many biological timeseries data are not stationary, which makes it difficult to analyze the instantaneous phase and amplitude. In the iTHEMS Biology seminar on February 17, I talked about Hilbert transform, which is known as a method to estimate the phase and the amplitude dynamics of nonstationary timeseries. First, I explained the mathematical background of the method. Then, I introduced some applications of this method to chronobiology, virus dynamics, and acoustic engineering. In this seminar, there were many questions and comments from audiences. Thank you very much!

20220309
Press ReleaseNegative string tension of a highercharge Schwinger model via digital quantum simulation
It is known that particles with the same positive (negative) charge usually are repulsed, while particles with opposite positive and negative charges are attracted to each other. Recently, however, it was pointed out that such "common knowledge" that an attractive force acts between particles with opposite positive and negative charges does not always hold true under special situations. The research group succeeded in realizing a situation in which a repulsive force acts between particles with opposite charges in a onedimensional quantum system called the Schwinger model by numerical simulation. This is a new application of the algorithm used in quantum computers (quantum algorithm), and is expected to contribute to our understanding of important problems such as the time evolution and the phase structure of the early universe in finite density regions, which have been difficult to analyze using conventional methods. For more details, please see the press release article from Kyoto University at related links.

20220309
Seminar ReportABBL/iTHEMS Astro Seminar by Dr. Yuta Sekino on February 18, 2022
On 18th Feb. 2022, Dr. Yuta Sekino gave an excellent introductory talk on Spin transport in ultracold atomic gases. In his talk, we discussed the usefulness of spin transport as a probe for manybody properties in ultracold atoms. In the first part, we focused on the conductivity of alternating spin current, which includes information on superfluid gap, pseudogap, and topological phase transition. In the latter part, we considered mesoscopic spin transport between two Fermi gases weakly connected with each other. Finally, we discussed similarities of ultracold atoms to neutron star matter. Reported by Shigehiro Nagataki

20220307
Press ReleaseSimulation Improves Accuracy of Forecasting Heavy Rainfall in Linear Precipitation Zones What if the most advanced weather radar could cover all of Kyushu
A joint research team led by Dr. Takemasa Miyoshi, Team Leader of the Data Assimilation Research Team at the RIKEN Center for Computational Science (RCCS) (Chief Scientist, Predictive Science Laboratory, Deputy Program Director, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS)), and Dr. Yasumitsu Maejima, Postdoctoral Researcher, has announced that simulation showed significant improvement of forecasting disastrous heavy rainfall in July 2020. The results of this study showed that the stateoftheart phasedarray weather radar can significantly improve the accuracy of forecasting heavy rainfall associated with linear precipitation zones. The results of this research are expected to improve the forecasting accuracy of linear precipitation zones, which are increasingly threatened by global warming, and to lead to the proposal of new forecasting techniques and observation systems to mitigate the damage. To read more, please see the related link.

20220303
Paper of the WeekWeek 1, March 2022
Title: Advances in QED with intense background fields Author: A. Fedotov, A. Ilderton, F. Karbstein, B. King, D. Seipt, H. Taya, G. Torgrimsson arXiv: http://arxiv.org/abs/2203.00019v1 Title: Nuclear force with LapH smearing Author: Takuya Sugiura, Yutaro Akahoshi, Tatsumi Aoyama, Takahiro M. Doi, Takumi Doi arXiv: http://arxiv.org/abs/2202.12532v1 Title: Weighted onelevel density of lowlying zeros of Dirichlet $L$functions Author: Shingo Sugiyama, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2201.00326v1 Title: Zeros of derivatives of $L$functions in the Selberg class on $\Re(s)<1/2$ Author: Sneha Chaubey, Suraj Singh Khurana, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2202.12126v1 Title: Entropies in $μ$framework of canonical metrics and Kstability, II  Nonarchimedean aspect: nonarchimedean $μ$entropy and $μ$Ksemistability Author: Eiji Inoue arXiv: http://arxiv.org/abs/2202.12168v1 Title: Revealing timeresolved particle acceleration in the recurrent Nova RS Ophiuchi Author: H.E.S.S. Collaboration (Naomi Tsuji) arXiv: http://arxiv.org/abs/2202.08201v1

20220303
Event ScheduleEvents for the 2nd week of March 2022
Thursday, March 10, 8:00– 9:30 External Event: Fundamentals Fest, mini Preevent on Science "Exploring and Bridging: The Potential of Basic Science" Thursday, March 10, 10:00– 11:00 iTHEMS Biology Seminar Thursday, March 10, 13:30– 15:00 NEW WG Seminar Friday, March 11, 12:30 13:30 Coffee Meeting Friday, March 11, 16:00 18:00 iTHEMS Math Seminar Saturday, March 12, 13:00 14:30 Special Lecture: 【Shigefumi Mori and Takashi Sakajo Special Talk】How is mathematics utilized in society?  Exploring the Essence of Mathematical Research

20220302
Person of the WeekSelfintroduction: Masato Itami
My name is Masato Itami, and I have joined iTHEMS as a visiting scientist in March 2022. I love stochastic things by nature, so I am currently studying the universal form of stochastic equations of motion for fluctuating objects in nonequilibrium systems. I am looking forward to interacting with people from various fields. By the way, my hobby is chess, so if you like chess, let's play chess together while/without talking about science.

20220301
Seminar ReportiTHEMS Biology Seminar by Dr. Ashley Nord and Dr. Rubén PérezCarrasco on February 24, 2022
Dr. Ashley Nord (Centre de Biologie Structurale/CNRS, France) and Dr. Rubén PérezCarrasco (Imperial College London, UK) gave a very interesting talk on the dynamics of stator units, the ion channels that generate torque for bacterial flagella. In the first half of the presentation, Dr. Ashley explained how the stator units produce torque once they are bound to the flagellar structure. Their experiment was able a) to track magnetic nanoparticles attached to E. coli flagella, and b) to set two initial conditions for the number of bound stator units. The work differs from the traditional views of the field because it shows  for the first time  the existence of two sets of relaxation times for stator units [1,2]. In the second part of the talk, Dr. Rúben discussed various stochastic models with asymmetric relaxation times to describe the dynamics of stator units. According to estimates via approximate Bayesian computation, the extended catch bond model with additional bound states performed better than other alternatives. If confirmed, their conclusion could give important hints and improve our understanding of biochemical processes in flagellar motors. Reported by Gilberto Nakamura

20220228
Seminar ReportQuantum Matter SG seminar by Dr. HongYan Shih on February 24, 2022
The Quantum Matter Study Group invited Dr. HongYan Shih from Academia Sinica to talk about the phase transitions of turbulence dynamics. In the beginning, she introduced the turbulence and the phase transition between laminar flow and turbulence. Surprisingly, this phase transition shares a unified picture with the predatorprey system. Then, she showed the connection between this fluid dynamics and the biosystem with the same university class. It is an inspiring interdisciplinary study. Reported by ChingKai Chiu

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Hot TopicFarewell message from Dr. Hiroyasu Miyazaki
Our colleague Hiroyasu Miyazaki moves on to a new carrier at NTT Communication Science Laboratories as of March 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Hiroyasu Miyazaki: My academic life is full of precious memories with iTHES and iTHEMS members. When I first joined the group, I was a bit worried since there were only a few mathematicians in RIKEN. But that was unnecessary. Everybody was very kind to me and every communication was really enjoyable. And the pleasure kept becoming larger and larger. I will certainly miss you and the heartwarming atmosphere in iTHEMS, but the life never stops. I am moving to a private research institute called NTTIFM (Institute for Fundamental Mathematics) on March 1st. I am supposed to work as a mathematician. So there will still be a lot of opportunities for discussion with you. If you will find me wandering in Wako campus (or anywhere else), please catch me and talk to me! Of course you are very welcome to visit NTTIFM if you are interested. Let’s keep in touch and see you again soon!

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Hot TopicWhat’s inside a black hole? UM physicist uses quantum computing, machine learning to find out
Dr. Enrico Rinaldi (iTHEMS Visiting Scientist) has been featured in institutional website. "Dude, what if everything around us was just … a hologram? The thing is, it could be—and a University of Michigan physicist is using quantum computing and machine learning to better understand the idea, called holographic duality." See related links for details.

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Seminar ReportiTHEMS Math Seminar by Dr. Genki Hosono on January 14, 2022
Dr. Genki Hosono gave us a stimulating talk on pluripotential and $L^2$ methods in complex geometry. The talk was carefully designed not only for nonmathematicians but also for experts around the topic. He began his talk with the definition and basic properties of subharmonic function and its multivariable version in complex geometry: plurisubharmonic function. He then introduced Bergman kernel and explained a variational approach to OhsawaTakegoshi $L^2$ extension theorem, which is an extension theorem of holomorphic function with a bound on $L^2$ norm weighted by a plurisubharmonic function. Finally he explained DengWangZhangZhou’s result on a `reverse direction’ of OhsawaTakegoshi theorem and his result with Inayama on a variant result. His explanations were very clear and quite valuable for us. Reported by Eiji Inoue

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Seminar ReportNEW WG Seminar by Mr. Takumi Hayashi on February 15, 2022
Takumi Hayashi (Tokyo/RESCEU) gave a talk on Lorenzian pathintegral approach to false vacuum decay [1]. Conventionally, false vacuum decay has been discussed within the Euclidean formalism developed by Coleman, but it may suffer from several subtle issues when applying to cosmological problems. Takumi proposed a new formulation for false vacuum decay and computed the bubble nucleation rate by directly evaluating a Lorenzian path integral based on the PicardLefschetz theory. Takumi discussed nucleation of bubbles with various sizes, not limited to the critical one only to which the Euclidean formalism can be applied, and showed that nucleation of small bubbles is more probable than the critical one. More than 20 physicists have joined the seminar and enjoyed fruitful discussions. Reported by Hidetoshi Taya

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Paper of the WeekWeek 3, February 2022
Revealing timeresolved particle acceleration in the recurrent Nova RS Ophiuchi H.E.S.S. Collaboration (Naomi Tsuji) arXiv: https://arxiv.org/abs/2202.08201 Title: Nonperturbative Waveguide Quantum Electrodynamics Author: Yuto Ashida, Takeru Yokota, Atac Imamoglu, Eugene Demler arXiv: http://arxiv.org/abs/2105.08833v4 Title: Isospin symmetry breaking in the charge radius difference of mirror nuclei Author: Tomoya Naito, Xavier RocaMaza, Gianluca Colò, Haozhao Liang, Hiroyuki Sagawa arXiv: http://arxiv.org/abs/2202.05035v1 Title: The double detonation of a double degenerate system, from Type Ia supernova explosion to its supernova remnant Author: Gilles Ferrand, Ataru Tanikawa, Donald C. Warren, Shigehiro Nagataki, Samar SafiHarb, Anne Decourchelle arXiv: http://arxiv.org/abs/2202.04268v1 Title: Detecting PreformedPair Current through Nonequilibrium Noise in the BCSBEC Crossover Author: Hiroyuki Tajima, Daigo Oue, Mamoru Matsuo, Takeo Kato arXiv: http://arxiv.org/abs/2202.03873v1

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Event ScheduleEvents for the 4th week of February 2022
Thursday, February 24, 17:00– 18:15 Quantum Matter Seminar Friday, February 25, 12:30 13:30 Coffee Meeting Friday, February 25, 18:00 18:30 External Event: RIKEN Day: Let's Talk with Researchers! "Listening to the Ringing of a Black Hole"

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Seminar ReportABBL/iTHEMS Astro Seminar by Dr. Yutaka Hirai on January 28, 2022
Dr. Yutaka Hirai gave an excellent talk on Galactic archaeology with rprocess elements. He showed that his highresolution simulations of galaxies suggest that binary neutron star mergers play an important role in enriching rprocess elements in dwarf galaxies and the Milky Way. He also showed that rprocess enhanced stars in the Milky Way tend to form in dwarf galaxies previously accreted to the Milky Way. He demonstrated that the abundance of rprocess elements in stars can be used as an indicator for the early evolution of the Milky Way. Reported by Shigehiro Nagataki

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Hot TopicThe Mysterious Forces Inside the Nucleus Grow a Little Less Strange
In the recent article posted in "Quanta magazine”, iTHEMS Director Tetsuo Hatsuda, visiting researcher Tetsuo Hyodo and their collaborator Laura Fabbietti in Munich are interviewed about the ongoing studies on the mysteries of nuclear forces using the Japanese supercomputers and the European Large Hadron Collider (LHC). See related links for details.
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