News
217 news in 2022
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2022-04-01
Person of the Week
Self-introduction: 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 two-dimensional 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 well-developed language in describing CFT and string theory.
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2022-03-31
Award
Dr. 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 !
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2022-03-31
Paper of the WeekWeek 5, March 2022
Title: Diffeomorphisms of 4-manifolds 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
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2022-03-31
Press Release
Chaos 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.
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2022-03-31
Hot Topic
iTHEMS NOW & NEXT FY2021 was held on March 25, 2022
The annual in-house 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.
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2022-03-30
Seminar Report
Quantum 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 Tg-protected Z2 Dirac points. In the beginning, by introducing the topological phase in the gapped and gapless systems, she discussed the conventional and Z2 Dirac points. Surprisingly, she established gauge-invariant charge formula and bulk-surface correspondence for Z2 Dirac points, which can give a full understanding about the topology of Tg-protected Z2 Dirac points. Then, she proposed the first Z2 Dirac material candidate Li2B4O7 for further exploration. Reported by Congcong Le
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2022-03-25
Event Schedule
Events 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
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2022-03-25
Seminar Report
How 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
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2022-03-24
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 4-manifolds 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
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2022-03-22
Hot Topic
Farewell 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.
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2022-03-22
Hot Topic
Farewell 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!
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2022-03-22
Hot Topic
Farewell 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 X-ray or gamma-ray 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!
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2022-03-22
Hot Topic
Farewell 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.
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2022-03-22
Hot Topic
Farewell 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 long-term 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 Program-Specific 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!
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2022-03-22
Seminar Report
iTHEMS 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 106 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
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2022-03-17
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 neutron-star 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
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2022-03-17
Event Schedule
Events 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
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2022-03-15
Seminar Report
iTHEMS 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
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2022-03-15
Seminar Report
iTHEMS Math Seminar by Dr. Shigenori Nakatsuka on January 28, 2022
Dr. Shigenori Nakatsuka from Kavli IPMU gave us a talk on dualities in W-superalgebras. In the first half of the talk he reviewed some basic concepts of vertex superalgebras, in particular W-superalgebras, and the Feigin--Frenkel duality, which states that the W-algebras in a certain class are isomorphic to the other W-algebras associated with the dual Lie algebras and the dual levels. In the latter half of the talk he introduced dualities beyond the Feigin--Frenkel duality including his recent work with Creutzig, Genra, and Sato. One of the remarkable results is the proof of the Feigin--Semikhatov conjecture, which gives a correspondence between the W-algebras associated with certain Lie algebras and the W-superalgebras associated with the corresponding Lie superalgebras. His talk was so stimulating that we could enjoy the mathematics of W-algebras. Reported by Mizuki Oikawa
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2022-03-11
Book
Mathematical 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 non-experts in biology or mathematics. Clear and concise structure that helps readers’ understanding.
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2022-03-11
Seminar Report
iTHEMS - R-CCS(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 - R-CCS(FTRT) Joint Seminar. He reported a functional renormalization group study of the three dimensional Ginzburg--Landau 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 first-order, but his conclusions suggest the possibility of a second-order phase transition. A lively discussion took place between the speakers and the audience on this interesting result. Reported by Tetsuo Hatsuda
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2022-03-10
Paper of the WeekWeek 2, March 2022
Title: Merger and post-merger of binary neutron stars with a quark-hadron crossover equation of state Author: Yong-Jia Huang, Luca Baiotti, Toru Kojo, Kentaro Takami, Hajime Sotani, Hajime Togashi, Tetsuo Hatsuda, Shigehiro Nagataki, Yi-Zhong Fan arXiv: http://arxiv.org/abs/2203.04528v1 Title: Tunable Dirac Semimetals with Higher-order 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 neutron-star mass and radius relation from the terrestrial nuclear experiments Author: Hajime Sotani, Nobuya Nishimura, Tomoya Naito arXiv: http://arxiv.org/abs/2203.05410v1
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2022-03-10
Seminar Report
Fundamentals Fest, mini Pre-event 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.
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2022-03-10
Seminar Report
iTHEMS 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 cell-cycle network system-Biological function originated in the law of localization-”. He showed us how mathematical analysis about the complex cell cycle networks can provide knowledge on non-trivial 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 G1-S and G2-M checkpoints in cell cycle. The analyses clarified that, even the two checkpoints are regulated by different protein complexes (Cdc2-Cdc13 and Cdc2-Cig2, 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
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2022-03-09
Award
The 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 higher-charge 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.
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2022-03-09
Seminar Report
iTHEMS Biology Seminar by Dr. Shingo Gibo on February 17, 2022
Many biological time-series 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 time-series. 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!
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2022-03-09
Press Release
Negative string tension of a higher-charge 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 one-dimensional 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.
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2022-03-09
Seminar Report
ABBL/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 many-body 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
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2022-03-07
Press Release
Simulation 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 (R-CCS) (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 state-of-the-art phased-array 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.
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2022-03-03
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 one-level density of low-lying 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 K-stability, II -- Non-archimedean aspect: non-archimedean $μ$-entropy and $μ$K-semistability Author: Eiji Inoue arXiv: http://arxiv.org/abs/2202.12168v1 Title: Revealing time-resolved particle acceleration in the recurrent Nova RS Ophiuchi Author: H.E.S.S. Collaboration (Naomi Tsuji) arXiv: http://arxiv.org/abs/2202.08201v1
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2022-03-03
Event Schedule
Events for the 2nd week of March 2022
Thursday, March 10, 8:00– 9:30 External Event: Fundamentals Fest, mini Pre-event 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
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2022-03-02
Person of the Week
Self-introduction: 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 non-equilibrium 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.
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2022-03-01
Seminar Report
iTHEMS Biology Seminar by Dr. Ashley Nord and Dr. Rubén Pérez-Carrasco on February 24, 2022
Dr. Ashley Nord (Centre de Biologie Structurale/CNRS, France) and Dr. Rubén Pérez-Carrasco (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
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2022-02-28
Seminar Report
Quantum Matter SG seminar by Dr. Hong-Yan Shih on February 24, 2022
The Quantum Matter Study Group invited Dr. Hong-Yan 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 predator-prey 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 Ching-Kai Chiu
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2022-02-22
Hot Topic
Farewell 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 heart-warming atmosphere in iTHEMS, but the life never stops. I am moving to a private research institute called NTT-IFM (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 NTT-IFM if you are interested. Let’s keep in touch and see you again soon!
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2022-02-22
Hot Topic
What’s inside a black hole? U-M 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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2022-02-21
Seminar Report
iTHEMS 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 non-mathematicians 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 Ohsawa-Takegoshi $L^2$ 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 Deng-Wang-Zhang-Zhou’s result on a `reverse direction’ of Ohsawa-Takegoshi 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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2022-02-21
Seminar Report
NEW WG Seminar by Mr. Takumi Hayashi on February 15, 2022
Takumi Hayashi (Tokyo/RESCEU) gave a talk on Lorenzian path-integral 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 Picard-Lefschetz 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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2022-02-17
Paper of the WeekWeek 3, February 2022
Revealing time-resolved 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 Roca-Maza, 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 Safi-Harb, Anne Decourchelle arXiv: http://arxiv.org/abs/2202.04268v1 Title: Detecting Preformed-Pair Current through Nonequilibrium Noise in the BCS--BEC Crossover Author: Hiroyuki Tajima, Daigo Oue, Mamoru Matsuo, Takeo Kato arXiv: http://arxiv.org/abs/2202.03873v1
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2022-02-17
Event Schedule
Events 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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2022-02-16
Seminar Report
ABBL/iTHEMS Astro Seminar by Dr. Yutaka Hirai on January 28, 2022
Dr. Yutaka Hirai gave an excellent talk on Galactic archaeology with r-process elements. He showed that his high-resolution simulations of galaxies suggest that binary neutron star mergers play an important role in enriching r-process elements in dwarf galaxies and the Milky Way. He also showed that r-process enhanced stars in the Milky Way tend to form in dwarf galaxies previously accreted to the Milky Way. He demonstrated that the abundance of r-process 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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2022-02-16
Hot Topic
The 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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2022-02-15
Seminar Report
iTHEMS Biology Seminar by Dr. Gilberto Nakamura on February 10, 2022
Stochastic processes describe systems in which one or more variables fluctuate randomly. In the first part of the talk, I reviewed basic concepts in stochastic processes and how to express them in terms of localized spin operators and the probability vector (PV). This framework is convenient to compute statistics away from meanfield approximations because it can borrow methods traditionally used in many-body problems in Physics. The second part of the talk addressed the equation for the squared norm of the PV and its correspondence with the Rényi entropy. The general idea and challenges of employing estimates of the Rényi entropy were discussed shortly after. As a practical biological application, I explained the dynamical equations for averages and fluctuations in a simple stochastic epidemic model, highlighting the effects of noise and correlations in heterogeneous finite systems.
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2022-02-14
Seminar Report
iTHEMS Biology Seminar by Dr. Takashi Okada on December 23, 2021
The Hidden Markov Models (HMM) have been used in a variety of fields for different purposes. I reviewed HMM and basic algorithms such as the forward algorithm. Then, I explained how this statistical framework can be applied to biological problems.
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2022-02-14
Research News
RIKEN Research: Modeling high-harmonic generation without resorting to perturbation theory
An advanced mathematical model that can describe high-energy interactions between light and matter has been developed by two RIKEN researchers and a collaborator [1]. The approach could be extended to offer new insights in other areas of physics. High-harmonic generation is a powerful technique that converts laser light from one wavelength, or color, to another. Put simply, it converts a low-energy, long-wavelength photon into multiple higher energy, shorter wavelength photons. High-harmonic generation has several applications. For example, it offers a way to create table-top sources of extreme ultraviolet or x-ray light using lasers, rather than expensive synchrotron facilities. High-harmonic generation can also produce ultrashort light pulses, as short as one attosecond ($10^{-18}$ second) or maybe even one zeptosecond ($10^{-21}$ second), which are useful for imaging extremely rapid processes such as those that occur in atoms. But high-harmonic generation is inherently difficult to model mathematically, and thus understand fully. Now, Hidetoshi Taya and Masaru Hongo from the RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) Program, together with their colleague Tatsuhiko Ikeda from the University of Tokyo, have developed an analytical approach to high-harmonic generation in the so-called non-perturbative regime for the first time. To read more, please visit the related link.
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2022-02-09
Hot Topic
"RIKEN AIP-Suri-joshi Joint Seminar" was held on January 29, 2022
On 29th January, a joint seminar of RIKEN AIP and Suri-Joshi took place and Ryosuke Iritani served as one of the guest speakers (including the iTHEMS affiliates Drs. Motoko Kato and Ade Irma Suriajaya). Unfortunately, the overwhelming COVID-19 situation in Tokyo did not allow for an in-person seminar as had been originally planned, which was indeed a bit disappointing for me. Nevertheless, thanks to the huge effort of AIP staff as well as Suri-Joshi organizers, we had a very successful talk session as well as Q&A session. I found the high diversity among the speakers considerably enriched our discussion. In this pandemic era, I can easily imagine many students struggling how to find dreams or what they want to be, which would have been already difficult even under normal circumstances. We emphasized that learning what you are interested in is a precious experience, which is the best motivating factor to work as a scientist. I hope the audience enjoyed our discussion, but as usual, I bet it was me who enjoyed best as-if one of the audience. I cannot thank too much to Suri-Joshi organizers and AIP staff for inviting me, to the speakers whom I was not able to meet in person this time but look forward to meeting in the near future, to the mathematically enthusiastic, professional announcer Naoko Shinozaki for her moderation of the sessions, and of course to the promising students who are deeply interested in learning and studying, for attending the seminar and asking excellent questions! Reported by Ryosuke Iritani
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2022-02-09
Paper of the WeekWeek 2, February 2022
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 Safi-Harb, Anne Decourchelle arXiv: http://arxiv.org/abs/2202.04268v1 Title: Detecting Preformed-Pair Current through Nonequilibrium Noise in the BCS--BEC Crossover Author: Hiroyuki Tajima, Daigo Oue, Mamoru Matsuo, Takeo Kato arXiv: http://arxiv.org/abs/2202.03873v1 Title: Delocalized spectra of Landau operators on helical surfaces Author: Yosuke Kubota, Matthias Ludewig, Guo Chuan Thiang arXiv: http://arxiv.org/abs/2201.05416v1 Title: Bounds in Nonequilibrium Quantum Dynamics Author: Zongping Gong, Ryusuke Hamazaki arXiv: http://arxiv.org/abs/2202.02011v1 Title: Universal constraint on nonlinear population dynamics Author: Kyosuke Adachi, Ryosuke Iritani, Ryusuke Hamazaki arXiv: http://arxiv.org/abs/2202.02028v1 Title: Impact of Dissipation on Universal Fluctuation Dynamics in Open Quantum Systems Author: Kazuya Fujimoto, Ryusuke Hamazaki, Yuki Kawaguchi arXiv: http://arxiv.org/abs/2202.02176v1
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2022-02-09
Event Schedule
Events for the 3rd week of February 2022
Monday, February 14, 13:00– 17:30 Workshop: Towards the Use of Data Assimilation for COVID-19 Investigations Monday, February 14, 15:00– 17:30 Workshop: MACS Colloquium Tuesday, February 15, 13:30– 15:00 NEW WG Seminar Friday, February 18, 12:30- 13:30 Coffee Meeting Friday, February 18, 14:00- 15:00 ABBL/iTHEMS Astro Seminar Friday, February 18, 16:30- 18:00 Seminar: iTHEMS - R-CCS(FTRT) Joint Online Seminar: Second order chiral phase transition in three flavor quantum chromodynamics?
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2022-02-08
Hot Topic
SSH Seminar "When high-school mathematics is useful in biology" was held on February 4, 2022
On February 4th, 2022, Ryosuke Iritani gave an online lecture on mathematical biology, entitled “高校で学ぶ数学が生物研究で活きるとき”（“when high-school mathematics is useful in biology”） for a Super Science High-school program at Takatsuki Junior and Senior High School. I started off with how a scientific career develops and what it is like to work as a scientist. I then delved into a scientific world, and demonstrated high school mathematics is a powerful tool to research in biology, drawing examples from the Fibonacci series in genetics, Price equation using recursive equations, game theory with matrix algebra, and kin selection theory for ants' society. I closed the talk with an encouragement for the motivated, budding scientists, that learning and studying are both extremely fun. I thank Kanda-sensei for inviting me to such a fantastic opportunity, as well as Suri-Joshi for giving me the opportunity to write an article that made this lecture possible by drawing Kanda-sensei's attention! Reported by Ryosuke Iritani
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2022-02-03
Paper of the WeekWeek 1, February 2022
Title: Spin relaxation rate for heavy quarks in weakly coupled QCD plasma Author: Masaru Hongo, Xu-Guang Huang, Matthias Kaminski, Mikhail Stephanov, Ho-Ung Yee arXiv: http://arxiv.org/abs/2201.12390v1 Title: Filtered instanton Floer homology and the homology cobordism group Author: Yuta Nozaki, Kouki Sato, Masaki Taniguchi arXiv: http://arxiv.org/abs/1905.04001v4 Title: Seifert hypersurfaces of 2-knots and Chern-Simons functional Author: Masaki Taniguchi arXiv: http://arxiv.org/abs/1910.02234v3 Title: Stable pairs and Gopakumar-Vafa type invariants on holomorphic symplectic 4-folds Author: Yalong Cao, Georg Oberdieck, Yukinobu Toda arXiv: http://arxiv.org/abs/2201.11540v1
217 news in 2022