News
170 news in 2023
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2023-05-04
Paper of the WeekWeek 1, May 2023
Title: Nonlinear chiral kinetic theory Author: Kazuya Mameda arXiv: http://arxiv.org/abs/2305.02134v1 Title: Spatial deformation of many-body quantum chaotic systems and quantum information scrambling Author: Kanato Goto, Taozhi Guo, Tomoki Nosaka, Masahiro Nozaki, Shinsei Ryu, Kotaro Tamaoka arXiv: http://arxiv.org/abs/2305.01019v1
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2023-05-02
Hot Topic
RIKEN iTHEMS signed a new MoU with Lawrence Berkeley National Laboratory (LBNL)
Reiner Kruecken (Director of the Nuclear Science Division of LBNL) and Tetsuo Hatsuda (Director of RIKEN iTHEMS) are the principal coordinators for LBNL and RIKEN iTHEMS, respectively, for this MoU [1]. The photo was taken in front of the desk of Ernest Lawrence [2], which is preserved at LBNL.
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2023-04-28
Person of the Week
Self-introduction: Rongyang Sun
My name is Rongyang Sun. I joined RIKEN in October 2021 as a Postdoctoral Researcher in R-CCS and RQC. Now, I am very glad to hold this concurrent position in iTHEMS. As a full-stack researcher in computational quantum many-body physics, my ultimate goal is to understand the fantabulous nature of quantum many-body systems by taking advantage of modern supercomputing systems and quantum computers. Towards this goal, I am developing advanced tensor network algorithms, maintaining high-performance tensor computing software, and applying these tools to the study of strongly correlated systems like interacting electrons and frustrated spins. Meanwhile, I am also exploring the possibility of utilizing near-term quantum computers to arrive at the same destination.
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2023-04-28
Person of the Week
Self-introduction: Tomonori Shirakawa
My name is Tomonori Shirakawa. I joined iTHEMS as a Senior Research Scientist in April 2023. I am interested in quantum many-body phenomena in condensed matter physics. To better understand quantum many-body phenomena, I have been working with various numerical methods. In particular, I have recently been exploring more efficient ways to solve quantum many-body problems using quantum-classical hybrid algorithms, quantum algorithms, and tensor network methods.
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2023-04-27
Seminar Report
iTHEMS Biology Seminar by Mr. Naoki Konno on April 20, 2023
In April 20, Mr Naoki Konno (University of Tokyo) gave a fantastic talk about the machine leaning method for the prediction of evolution. The talk was entitled, “Machine learning predicts biological system evolution by gene gains and losses”. To my knowledge, this study using genome data of ~3000 species is one of few seminal attempts to theoretically predict long-term and system-level evolution. The seminar by Konno san was very clear and we understood the predictability of the proposed framework, called “Evodictor”. In the beginning of the talk, he kindly explained the theoretical basis about phylogenetic tree estimation and machine learning for non-specialists for which we could enjoy and learn from his seminar a lot. Thank you, Konno-san for the great talk!! Reported by Gen Kurosawa
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2023-04-24
Research News
RIKEN Research: Quantum ‘magic’ could help explain the origin of spacetime
A quantum property dubbed ‘magic’ could be the key to explaining how space and time emerged, a new mathematical analysis by three RIKEN physicists suggests. It’s hard to conceive of anything more basic than the fabric of spacetime that underpins the Universe, but theoretical physicists have been questioning this assumption. “Physicists have long been fascinated about the possibility that space and time are not fundamental, but rather are derived from something deeper,” says Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS). To read more, please visit the related link.
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2023-04-24
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Kumiko Kotera on April 18, 2023
We are living exciting times: we are now able to probe the most violent events of the Universe with diverse messengers (cosmic rays, neutrinos, photons and gravitational waves). One challenge to complete the multi-messenger picture resides in the highest energies, as no ultra-high energy neutrinos have been observed yet. This challenge could be undertaken by the GRAND (Giant Radio Array for Neutrino Detection) project, which aims at detecting ultra-high energy particles, with a colossal array of 200'000 antennas over 200'000 km2, split into ~20 sub-arrays of ~10'000 km2 deployed worldwide. In this talk, Kumiko Kotera presented preliminary designs and simulation results, plans for the ongoing, staged approach to construction, and the rich research program made possible by the proposed sensitivity and angular resolution. Reported by Shigehiro Nagataki
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2023-04-20
Paper of the WeekWeek 4, April 2023
Title: Investigating Time Evolution of Thermal Emission from the Putative Neutron Star in SN 1987A for 50+ Years Author: Akira Dohi, Emanuele Greco, Shigehiro Nagataki, Masaomi Ono, Marco Miceli, Salvatore Orlando, Barbara Olmi arXiv: http://arxiv.org/abs/2304.08418v1 Title: The Impacts of Neutron-Star Structure and Base Heating on Type I X-Ray Bursts and Code Comparison Author: Guoqing Zhen, Guoliang Lv, Helei Liu, Akira Dohi, Bobuya Nishimura, Chunhua Zhu, Liyu Song, Weiyang Wang, Renxin Xu arXiv: http://arxiv.org/abs/2304.07197v1 Title: Plausible presence of new state in neutron stars with masses above 0.98MTOV Author: Ming-Zhe Han, Yong-Jia Huang, Shao-Peng Tang, Yi-Zhong Fan doi: https://doi.org/10.1016/j.scib.2023.04.007 arXiv: http://arxiv.org/abs/2207.13613v2
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2023-04-17
Research News
RIKEN Research: Gravitational waves could indicate transition to strange quark matter
Telltale signatures in gravitational-wave signals from merging neutron stars should reveal what happens to matter at the extreme pressures generated during such mergers, calculations by RIKEN researchers predict [1]. If you took some water and compressed it with a piston, it would shrink as the molecules get pushed closer together. If you continued ramping up the pressure, you’d reach a point where the atoms collapse and form an ultra-dense soup of neutrons and protons. The only place in the Universe where this happens is neutron stars, the collapsed remnants of burned-out stars, and it produces mind-boggling densities—one teaspoon of such material weighs several hundred billion kilograms. But what would happen if you continued to increase the pressure still further? Not even astrophysicists know the answer to that. To read more, please visit the related link.
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2023-04-13
Paper of the WeekWeek 3, April 2023
Title: Observing Supernova Neutrino Light Curves with Super-Kamiokande. IV. Development of SPECIAL BLEND: a New Public Analysis Code for Supernova Neutrinos Author: Akira Harada, Yudai Suwa, Masayuki Harada, Yusuke Koshio, Masamitsu Mori, Fumi Nakanishi, Ken'ichiro Nakazato, Kohsuke Sumiyoshi, Roger A. Wendell arXiv: http://arxiv.org/abs/2304.05437v1 Title: From diffeomorphisms to exotic phenomena in small 4-manifolds Author: Hokuto Konno, Abhishek Mallick, Masaki Taniguchi arXiv: http://arxiv.org/abs/2304.05997v1 Title: Gamma-Ray Emission in the Seyfert Galaxy NGC 4151: Investigating the Role of Jet and Coronal Activities Author: Yoshiyuki Inoue, Dmitry Khangulyan arXiv: http://arxiv.org/abs/2304.04138v1
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2023-04-13
Seminar Report
Seminar, "Introduction to the Renormalization group method as a powerful reduction method of dynamics" by Dr. Teiji Kunihiro on April 10, 2023
In April 10, Dr Teiji Kunihiro (Prof Emeritus, Kyoto Univ) gave an introductory talk about the renormalization group method, entitled “Introduction to the Renormalization group method as a powerful reduction method of dynamics.” In fact, this talk was the first seminar at our new seminar room #359 with the splendid black-board in RIKEN Wako Campus. The talk by Kunihiro-san using the black-board was very very clear, and we can understand the power of the Renormalization group method and its applicability [1]. The talk was also delivered via Zoom (i.e. ~35 participants in total), and there were lively discussions between the lecturer and the audience. After the talk, he kindly shared his lecture note with us so that we can take advantage of it. Thank you, Kunihiro-san for the wonderful talk!! Reported by Gen Kurosawa
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2023-04-11
Seminar Report
Lab-Theory Standing Talks #1 by Dr. Hideshi Ooka on March 16, 2023
The first Lab-Theory standing talk took place on March 16th, 2023, inviting Hideshi Ooka from CSRS (Riken Center for Sustainable Resource Science). He picked up the chemical process of making hydrogen from water as the subject. By design, the event is organized in a very informal setting."I was glad that the speaker prepared very few slides and all the slides were simple because it gave the audience an opportunity to ask many random questions in all sorts of direction," one of the participants, Catherine Beauchemin says. As she says, "in this light and flexible format, it is the audience that can decide what aspects are more interesting for them and ask more questions about it," there have been many questions asked and discussions followed. The event appears to be fruitful for the speaker too; "I will share the comment with my colleagues, as I believe it is a chance to advance the level of chemistry in our lab, " Hideshi Ooka concludes. Reported by Tsukasa Tada
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2023-04-10
Person of the WeekSelf-introduction: Seishiro Ono
My name is Seishiro Ono. I received my Ph.D. from the University of Tokyo in March 2023, and then I joined RIKEN iTHEMS in April 2023. My research interests lie in quantum condensed matter physics. I have been fascinated by the diversity of this field, and I am eager to understand the various phenomena from a unified point of view. I am currently investigating a unified understanding of superconductivity based on symmetry and topology. In addition, I have recently become interested in experimental signatures of topological nature, applications of machine learning to materials science, and quantum simulation of strongly correlated systems.
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2023-04-07
Seminar Report
iTHEMS Biology Seminar by Dr. Yohei Nakayama on March 30, 2023
On March 30th, Dr. Nakayama talked about F1-ATPase from both experimental and theoretical aspects. In the introduction, he reviewed biological molecular motors and experimental facts. Then he introduced a Langevin model for the kinetics of F1 and explained how a specific case of the model fits the previous experiments. In the main part, he told us about new experimental results, relation to the theoretical model, and theoretical prediction based on the model. We thank Dr. Nakayama for giving us an exciting presentation. Reported by Kyosuke Adachi
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2023-04-07
Person of the Week
Self-introduction: Zixia Wei
My name is Zixia Wei, and I got my Ph.D. from Yukawa Institute, Kyoto University in March 2023. I work on many different aspects of the AdS/CFT correspondence. The AdS/CFT correspondence relates a gravitational theory to a non-gravitational theory in a lower-dimensional system. Recently, I am interested in studying statistical physics with the help of the AdS/CFT correspondence. Thermal states in non-gravitational systems, which are often the targets of statistical physics, are related to black holes via the AdS/CFT correspondence. Obvious observations in black holes are sometimes nontrivial when translated back to statistical systems. I am working on making nontrivial conjectures in general statistical systems by considering black holes and then trying to prove them back in statistical systems.
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2023-04-06
Paper of the WeekWeek 2, April 2023
Title: Atiyah-Hirzebruch spectral sequence for topological insulators and superconductors: E2 pages for 1651 magnetic space groups Author: Ken Shiozaki, Seishiro Ono arXiv: http://arxiv.org/abs/2304.01827v1 Title: Frobenius algebras associated with the α-induction for equivariantly braided tensor categories Author: Mizuki Oikawa arXiv: http://arxiv.org/abs/2303.11845v1 Title: Involutions, links, and Floer cohomologies Author: Hokuto Konno, Jin Miyazawa, Masaki Taniguchi arXiv: http://arxiv.org/abs/2304.01115v1
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2023-04-06
Person of the Week
Self-introduction: Che-Yu Chen
Hi, my name is Che-Yu Chen, a Taiwanese researcher, joining RIKEN iTHEMS as an SPDR in April 2023. I got my Ph.D. in Physics from National Taiwan University in 2019. After my graduation, I stayed as a postdoc at LeCosPA-NTU (2019-2020) and then became an AS postdoc at the Institute of Physics, Academia Sinica (2020-2023), before coming to RIKEN. My interest is mainly in gravitational physics, including modified gravity and the phenomenological aspects of quantum gravity. In particular, I'm currently working on using state-of-the-art black hole observations to test general relativity (GR), or even to probe putative non-GR physics. The direct detection of gravitational waves emitted from binary black hole mergers, and the images of supermassive black holes, have ushered in a completely new era in which directly probing spacetimes near black holes becomes possible. There are several interesting non-GR physics, some of which could even be motivated by quantum gravitational effects. These non-GR physics could induce non-trivial or even unique imprints on gravitational waveforms and black hole images, and hence can possibly be tested in the future. A better understanding of this topic can tell us how well GR describes such extreme spacetime regimes, and if it were to be modified, which direction is more observationally preferred. I'm looking forward to the fruitful discussions with the iTHEMS members in the future.
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2023-04-05
Person of the Week
Self-introduction: Tomoya Nagai
My name is Tomoya Nagai. I joined as a coordinator in April 2023. I started working after getting the Ph.D. in astrophysics and have worked in science communication, R&D strategy development, research funding and R&D management. Until March 2023, I worked at KEK and Kobe University, where I was manager of research projects using the supercomputers “Fugaku". I will do my best to help you in your research.
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2023-04-05
Person of the Week
Self-introduction: Tingyu Zhang
My name is Tingyu Zhang, and I joined iTHEMS as a junior research associate in April 2023. Now I am involved in a PhD program in physics at the University of Tokyo. I mainly focus on the study of quantum many-body systems and non-equilibrium physics. Specifically I’m now studying the transport phenomena in cold atomic systems, through Green’s function methods and the perturbation theory. I’m looking forward to discussing physics with other researchers in the future.
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2023-03-31
Press Release
Predicting crypto asset price bursts using the correlation tensor of trading networks - towards secure crypto assets and the digital economy -
Cryptoassets are becoming an integral part of the digital economy. RIKEN and Kyoto University are collaborating on theoretical research to detect anomalous events such as money laundering and fraud, and to predict price bursts, by making full use of the mathematical science of networks. A research group led by Yuichi Ikeda (Professor at Kyoto Univ.), Abhijit Chakraborty (Assistant Professor at Kyoto Univ. and Visiting Research Scientist at RIKEN iTHEMS) and Tetsuo Hatsuda (RIKEN iTHEMS), has developed a novel method to analyse the spectrum of the correlation tensor corresponding to a trading network for cryptographic assets, and has developed a new method for predicting price bursts. They found that the maximum singular value of the tensor shows a significant negative correlation with the price of cryptoasset prices. Using this finding, the group gained the prospect of providing an early indicator of price bursts. For details, please refer to Kyoto University's press release article at the related links below.
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2023-03-31
Award
Dr. Thomas Hitchcock received the "Best English Presentation Award" of Ecological Society of Japan
Thomas Hitchcock (SPDR, iTHEMS) received the "Best English Presentation Award" at the 70th Annual meeting of the Ecological Society of Japan (ESJ) held on March 2023 for his presentation on "Paternal genome elimination promotes altruism in viscous populations". Congratulations, Thomas!
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2023-03-31
Award
Dr. José Said Gutiérrez-Ortega received the "Excellent English Presentation Award" of Ecological Society of Japan
José Said Gutiérrez-Ortega (SPDR, iTHEMS) received the "Excellent English Presentation Award" at the 70th Annual meeting of the Ecological Society of Japan (ESJ) held on March 2023 for his presentation on "Disparate patterns of niche evolution in the diversification of the Neotropical cycad genus Ceratozamia (Zamiaceae)". Congratulations, José !
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2023-03-31
Hot TopicMessages from Tetsuo Hatsuda (March 31, 2023)
Dear iTHEMS members Today is the last day of FY2022. I would like to express my deepest gratitude to all of you for your efforts in overcoming the pandemic this year and continuing your research activities. I would also like to thank the following people who physically have left or are leaving iTHEMS for their great contributions to iTHEMS during FY2022. Bon Voyage! Etsuko Itou, Masaki Taniguchi, Naritaka Oshita, Takuya Sugiura, Yuki Yazaki, Matthias Berwein, Akira Matsumoto, Chris Bourne, Michiya Mori, Shou Yoshikawa, Don Warren, Shunsuke Kobayashi, Hiroshi Yokota, Gilberto Nakamura, Kazumi Kuwata. With best regards, Tetsuo Hatsuda
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2023-03-29
Award
The paper co-authored by Dr. Ryosuke Iritani has been selected as "Editors' Choice" of OIKOS
The paper entitled "Species interactions and diversity: a unified framework using Hill numbers" co-authored by Dr. Ryosuke Iritani (Research Scientist, iTHEMS) has been selected as the Editors' Choice in OIKOS. Congratulations!
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2023-03-29
Book
Condensed Matter Physics and Topology - From the Viewpoint of Noncommutative Geometry
Author: Yosuke Kubota Language: Japanese
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2023-03-28
Hot Topic
Farewell message from Dr. Euki YAZAKI
Our colleague Euki YAZAKI will move to the Research Center for Advanced Analysis, National Agriculture and Food Research Organization as a Research Scientist from April 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Euki YAZAKI: As I prepare to leave after three wonderful years at RIKEN, I would like to take this opportunity to express my gratitude to all of you. It has been an honor to work with such a wonderful group of theoretical and mathematical scientists and I have learned so much from each and every one of you. I would like to thank all my colleagues who have supported me during my time at iTHEMS. Your expertise and enthusiasm have been invaluable, and I am grateful for the time I have spent with you. I would also like to thank the staff at iTHEMS support for their many supports. Although I will be moving on to new adventures, I hope to continue to enjoy good research with iTHEMS members in the future.
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2023-03-27
Seminar Report
iTHEMS Biology Seminar by Dr. Midori Tuda on March 23, 2023
Dr. Tuda gave us a very well-prepared, clear and interesting presentation about her group's current research. Her work is primarily experimental, while iTHEMS Biology members' work is primarily theoretical, which could create interesting opportunities. We found many common interest between her research and that of iTHEMS Biology members, such as niche divergence under a changing climate (Gutiérrez-Ortega), sex ratio of offsprings (Hitchcock), and species co-existence/competition (Iritani). This gave rise to many interesting questions, comments and exchanges. We hope to continue conversation. Reported by Catherine Beauchemin
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2023-03-23
Paper of the WeekWeek 4, March 2023
Title: Gradient-flowed order parameter for spontaneous gauge symmetry breaking Author: Kengo Kikuchi, Kenji Nishiwaki, Kin-ya Oda arXiv: http://arxiv.org/abs/2303.10841v1 Title: Toric non-archimedean μ-entropy and thermodynamical structure Author: Eiji Inoue arXiv: http://arxiv.org/abs/2303.09090v1
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2023-03-23
Hot Topic
Farewell message from Dr. Akira Matsumoto
Our colleague Akira Matsumoto will move to the Yukawa Institute for Theoretical Physics, Kyoto University as a Program-Specific Researcher from April 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Akira Matsumoto: I have been a member of iTHEMS for almost one year, which is the first opportunity for me to work as a postdoc. In spite of the difficult situation of COVID-19, I was able to enjoy research activity thanks to a good environment of iTHEMS and great effort by assistants. It is interesting to join seminars and discussions freely with researchers from various fields. I would like to thank all the iTHEMS members for giving me nice experiences. I plan to be a visiting scientist of iTHEMS after leaving RIKEN. I am very happy to keep in contact with iTHEMS members and looking forward to collaboration in the future.
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2023-03-22
Award
Dr. Yalong Cao received FY2022 RIKEN Excellent Achievement Award
Yalong Cao (Research Scientist, iTHEMS) received the FY2022 RIKEN BAIHO Award (梅峰賞) (RIKEN Excellent Achievement Award" for his excellent achievement on "Study of Donaldson-Thomas Invariants on Calabi-Yau 4-folds". Congratulations!
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2023-03-16
Paper of the WeekWeek 3, March 2023
Title: Coupled Hénon Map, Part II: Doubly and Singly Folded Horseshoes in Four Dimensions Author: Jizhou Li, Keisuke Fujioka, Akira Shudo arXiv: http://arxiv.org/abs/2303.06824v1 Title: Coupled Hénon Map, Part I: Topological Horseshoes and Uniform Hyperbolicity Author: Keisuke Fujioka, Ryota Kogawa, Jizhou Li, Akira Shudo arXiv: http://arxiv.org/abs/2303.05769v1
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2023-03-16
Hot Topic
Farewell message from Dr. Hiroshi Yokota
Our colleague Hiroshi Yokota has moved to the Graduate School of Human and Environmental Studies, Kyoto University as a CREST postdoctoral researcher from March 1, 2023. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Hiroshi Yokota: I had worked at iTHEMS as a postdoctoral researcher for almost 4 years. I would like to thank all the iTHEMS members for the valuable discussions on their researches including my own research. Moreover, in iTHEMS, I had very good opportunities to attend the exciting seminars and colloquiums which gave me brilliant ideas from the various fields: physics, biology, mathematics and information. I enjoyed the discussions, the seminars and the colloquiums in iTHEMS. I also would like to thank all assistants who gave us the comfortable research environment. Fortunately, I am allowed to be the visiting scientist in iTHEMS. I hope to discuss with iTHEMS members in future also.
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2023-03-15
Hot Topic
Farewell message from Dr. Naritaka Oshita
Our colleague Naritaka Oshita will move to the Kyoto University as a Hakubi assistant professor from April 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Naritaka Oshita: I enjoyed studying gravity and black holes while being a part of iTHEMS and participating in some iTHEMS events and activities. As of the end of this March, it has been almost two years since I started my second postdoc at iTHEMS as an SPDR fellow in 2021 April. From 2023 April, I will be a Hakubi assistant professor at Kyoto University and will start my exciting new research to understand the mystery of gravity. I enjoyed discussing with many iTHEMS members who are working on physics, biology, mathematics, (quantum) information theory, etc. I thank all faculties, researchers, and students at iTHEMS for having exciting discussions with me! iTHEMS assistants have been contributing to this group to improve the research environment at iTHEMS and they kindly helped me a lot when I needed their help and was in trouble. I appreciate all the assistants at iTHEMS for their support and for having fun conversations! Again, thank you to all members at iTHEMS for everything! I will still be a part of iTHEMS as a visiting researcher. I hope I can have exciting discussions and conversations with you in the future. See you again!
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2023-03-15
Research News
RIKEN NEWS: Interview with Special Postdoctoral Researcher (2): A great first step as a mathematician at the age of 38
Taketo Sano (Special Postdoctoral Researcher, iTHEMS) is interviewed on the RIKEN website. RIKEN has a Special Postdoctoral Researchers Program, which allows young researchers to work independently on a research theme of their own choice and free thinking, with the aim of fostering researchers who will be active internationally. We took this opportunity to interview senior researchers and current researchers who are active in their respective fields. In this second installment, we interview Taketo Sano, a Special Postdoctoral Researcher, iTHEMS. To read more, please see the related link.
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2023-03-13
Hot Topic
Farewell message from Dr. Masaki Taniguchi
Our colleague Masaki Taniguchi will move to the Kyoto University as an assistant professor from April 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Masaki Taniguchi: I'd like to thank the program director and assistants for many helpful supports over these three years and also many research members for discussing with me. I spent three years in iTHEMS as a mathematical researcher(SPDR). During the three years, I could concentrate on doing my research and communicating with researchers in other fields. In particular, I had been attending a weekly seminar focusing on interactions between math and physics. It was a valuable experience to feel various viewpoints from physics. Also, I got a chance to give a presentation at an event of RIKEN for high school or junior high school students. In my final year, I was chosen as a research member of a program at MSRI and spent four months at Berkeley to communicate with many researchers in my field. I could also invite several researchers to the math seminar and had good opportunities to promote research. I appreciate a good environment in iTHEMS so that I could have these experiences. From this April, I’ll be an assistant professor at Kyoto University. But, I still have several collaborators in iTHEMS, so I’d like to continue discussing with many researchers in iTHEMS as a visiting researcher.
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2023-03-13
Hot Topic
Farewell message from Dr. Etsuko Itou
Our colleague Etsuko Itou will move to the Yukawa Institute for Theoretical Physics, Kyoto University as an associate professor from April 1st. We all will miss her and wish her the best of luck in her latest endeavor. Here is a message from Etsuko Itou : I worked at iTHEMS for almost a year as a senior research scientist. I had the opportunity to discuss researches with people from various backgrounds, go on a short trip to Kawagoe, and give presentations at interdisciplinary research meetings, which was a valuable experience for me. I would also like to thank my assistants and PR staff for their support! I will be a visiting scientist of iTHEMS next year. I look forward to working with you again.
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2023-03-13
Hot Topic
Interdisciplinary Science Conference in Okinawa (ISCO 2023) on February 27, 2023
On Feb.27 (Mon)-March 3 (Fri), ISCO 2023 (Interdisciplinary Science Conference in Okinawa 2023 - Physics and Mathematics meet Medical Science -) was held at OIST (Okinawa Institute of Science and Technology). The conference was co-hosted by RIKEN iTHEMS, Kavli IPMU and OIST, with 135 participants inside and outside Japan. This was the first in-person conference held in OIST after the Covid-19 pandemic. There were 28 invited talks and 9 contributed talks. From RIKEN iTHEMS, Gordon Baym, Catherine Beauchemin, Gen Kurosawa, Hiro Nagataki, Hidetoshi Nishimori, Tomoki Ozawa, and Takashi Tsuboi gave scientific talks, and Tetsuo Hatsuda gave a closing remark. The purpose of ISCO 2023 was to bring together leading researchers in the fields of physics, astrophysics, mathematics, data science, life science, environmental science, and medical science, and to discuss the latest advancements in their respective fields. In addition to the presentations held at the OIST auditorium, a tour inside the OIST campus as well as a special lecture about Sharks by Dr. K. Sato at Churaumi Aquarium were held. Participants have intensive discussions beyond the disciplines at the plenary, poster, and lunch sessions. Some of the presentation slides can be downloaded from the ISCO 2023 webpage.
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2023-03-13
Hot Topic
RIKEN-Nara Women's University Joint Diversity Promotion Workshop was held on March 7, 2023
On March 7 and 8, sophomores, juniors, and seniors (16 students in total) from the Faculty of Science at Nara Women's University visited RIKEN's Kawakami Laboratory, Hou Laboratory, iTHEMS, RIBF facility, and Miyawaki Laboratory. In addition to experiencing some of the cutting-edge research at each of these laboratories, they had the opportunity to ask more in-depth questions about their research and learn about the daily lives of RIKEN researchers during a social event held in the evening of the first day of the program. It was also an opportunity for students from different courses in the Faculty of Science at Nara Women's University, including mathematics, physics, biology, and environmental chemistry, to interact with each other beyond their grade level. This diversity promotion activity is part of the RIKEJO training program jointly promoted by the Faculty of Science at Nara Women's University and RIKEN iTHEMS, and is combined with a series of lectures at Nara Women's University, and will be continued in the next fiscal year and beyond.
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2023-03-13
Research News
RIKEN Research: Explanation found for puzzling observation of Shiba states in superconductors
The origin of a mysterious experimental observation in a superconductor with a magnetic impurity sitting on top of it has been revealed in a theoretical study by a RIKEN researcher and a collaborator. This could help realize a robust quantum state residing in a superconductor that may find application in quantum computers. Superconductors conduct electricity without any resistance because electrons in them form pairs that have an energy gap. But placing a magnetic atom on top of a superconductor creates a new state in this energy gap as a result of the atom’s magnetism interacting with the superconductor’s paired electrons. Known as the Yu–Shiba–Rusinov state, or Shiba state for short, this state has been attracting a lot of interest because it could shed light on the emergence of a special state in a topological superconductor called the Majorana zero mode, which is promising for realizing fault-tolerant quantum computing. To read more, please visit the related link.
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2023-03-13
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Ellis Owen on March 10, 2023
Ultra high-energy (UHE) cosmic rays (CRs) from distant sources interact with intergalactic radiation fields, leading to their spallation and attenuation through photo-hadronic processes. Their deflection and diffusion in large scale intergalactic magnetic fields (IGMFs), in particular those associated with Mpc-scale structures, alter the cumulative cooling and interactions of a CR ensemble to modify their spectral shape and composition observed on Earth. In this talk, Ellis Owen demonstrated the extent to which IGMFs can affect observed UHE CRs, and showed that source population models are degenerate with IGMF properties. Interpretation of observations, including the endorsement or rejection of any particular UHE CR source classes, needs careful consideration of the structural properties and evolution of IGMFs. Future observations providing tighter constraints on IGMF properties will significantly improve confidence in assessing UHE CR sources and their intrinsic CR production properties. Reported by Shigehiro Nagataki
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2023-03-09
Paper of the WeekWeek 2, March 2023
Title: Empirical neutron star mass formula based on experimental observables Author: Hajime Sotani, Tomoya Naito arXiv: http://arxiv.org/abs/2303.03631v1 Title: On the regularity conditions for holographic nonlinear responses: electric conductivity and friction coefficient Author: Shuta Ishigaki, Shin Nakamura, Kazuaki Takasan arXiv: http://arxiv.org/abs/2303.02633v1 Title: Neutron star mass-radius constraints using the high-frequency QPOs of GRB 200415A Author: H. Sotani, K. D. Kokkotas, N. Stergioulas arXiv: http://arxiv.org/abs/2303.03150v1
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2023-03-07
Seminar Report
iTHEMS Biology Seminar by Dr. Adrian Gonzalez-Casanova on January 19, 2023
We had the pleasure to have Dr. Adrián González-Casanova (Neyman Visiting Assistant Professor, The University of California, Berkeley, USA / Associate Professor, National Autonomous University of Mexico, Mexico) in our Biology seminar of January 19th, 2023. He presented us a talk consisting of two sections. First, he explained to us the basis of the coalescent theory: a model that depicts how alleles within a population relate each other until reaching a common ancestor. Second, he presented us how the coalescent theory can be used to explain and predict the behavior of one of the most intriguing experiments in evolutionary biology: the Lenski experiment. The Lenski experiment consists of a daily cultivation of E. coli; each day's culture is grown from a population cultivated the previous day. This, way, after thousand generations, the experiment has shown that the fitness increase of individuals is decelerating, but it doesn't decrease or even reach a plateau. Dr. González-Casanova presented us some ideas of how we can model the underlying biological processes behind the experiment while considering other noisy processes such as epistasis or clonal interference, and thus better understand how evolution occurs. Reported by José Said Gutiérrez-Ortega
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2023-03-03
Seminar ReportQuantum Matter Seminar by Dr. Yung-Yeh Chang on March 2, 2023
On March 2nd, 2023, the iTHEMS Quantum Matter Seminar was held online, featuring a talk on "Topological Kondo Superconductors" by Yung-Yeh Chang, a postdoctoral researcher at the National Center for Theoretical Sciences and National Yang Ming Chiao Tung University in Taiwan. Yung-Yeh Chang began by introducing Kondo lattice and heavy fermion compound. Interestingly, superconductivity can emerge in this compound. Then, including topology, he proposed a realization of a 2D time-reversal symmetric superconductor in a class of Kondo lattice materials. The proposed system involves the odd-parity Kondo hybridization, which mediates ferromagnetic spin-spin coupling and leads to spin-triplet resonant-valence-bond (t-RVB) pairing between local moments. The speaker explained that spin-triplet p±p' wave topological superconductivity is reached when the Kondo effect co-exists with t-RVB. By using the mean field theory to generate an effective free fermion (BdG) Hamiltonian, the topological nature was identified by the non-trivial topological invariant and the chiral Majorana modes at edges. The results on the superconducting transition temperature, Kondo coherent scale, and onset temperature of Kondo hybridization were discussed, which not only qualitatively but also quantitatively agree with the observations for UTe2. In summary, the iTHEMS Quantum Matter Seminar on "Topological Kondo Superconductors," presented by Yung-Yeh Chang, provided an insightful discussion on the study of topological superconductors in Kondo lattice materials. The attendees had the opportunity to ask questions and engage in discussions with the speaker, making it an interactive and informative seminar. Reported by Chen-Hsuan Hsu (Academia Sinica, Taiwan) and Ching-Kai Chiu
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2023-03-02
Paper of the WeekWeek 1, March 2023
Title: On the Zeeman Effect in Magnetically-Arrested Disks Author: Yoshiyuki Inoue arXiv: http://arxiv.org/abs/2302.14403v1 Title: Electric-field driven nonequilibrium phase transitions in AdS/CFT Author: Daisuke Endo, Yuichi Fukazawa, Masataka Matsumoto, Shin Nakamura arXiv: http://arxiv.org/abs/2302.13535v1
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2023-02-23
Paper of the WeekWeek 4, February 2023
Title: Color superconductivity on the lattice -- analytic predictions from QCD in a small box Author: Takeru Yokota, Yuta Ito, Hideo Matsufuru, Yusuke Namekawa, Jun Nishimura, Asato Tsuchiya, Shoichiro Tsutsui arXiv: http://arxiv.org/abs/2302.11273v1 Title: From Entropy to Echoes: Counting the quasi-normal modes and the quantum limit of silence Author: Naritaka Oshita, Niayesh Afshordi arXiv: http://arxiv.org/abs/2302.08964v1 Title: A simple method for multi-body wave function of ground and low-lying excited states using deep neural network Author: Tomoya Naito, Hisashi Naito, Koji Hashimoto arXiv: http://arxiv.org/abs/2302.08965v1 Title: Scrambling and Recovery of Quantum Information in Inhomogeneous Quenches in Two-dimensional Conformal Field Theories Author: Kanato Goto, Masahiro Nozaki, Shinsei Ryu, Kotaro Tamaoka, Mao Tian Tan arXiv: http://arxiv.org/abs/2302.08009v1 Title: Effects of Coulomb and isospin symmetry breaking interactions on neutron-skin thickness Author: Tomoya Naito, Gianluca Colò, Haozhao Liang, Xavier Roca-Maza, Hiroyuki Sagawa arXiv: http://arxiv.org/abs/2302.08421v1
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2023-02-20
Seminar Report
DMWG Seminar by Dr. Jowett Chan on February 9, 2023
Dark matter (DM) of our Universe could be categorized into three types: cold DM (CDM), warm DM (WDM), or fuzzy DM (FDM) depending on its mass. CDM is the most well-studied one with its success in large-scale structure formations. However, as studies proceed, some problems arise in such models: observations of small-structure would not match the predictions of CDM structures in simulations. For example, observations of Milky Way satellites indicate the existence of the central core while simulations predict cuspy structures at the center. The feature could be well-described by considering FDM of m~O(1e-20) eV or below. The unique point of FDM is that the mass of the particle becomes a unique parameter for calculation. In numerical simulations of FDM halos, we can see the formation of cores in the Hubble time (i.e. the age of the Universe) and relaxations of radial structures. As the test particle mass gets larger, core-formation time becomes longer. One possible caveat for FDM models is the so-called "diversity problem". Our satellite galaxies show diversity in their core structures, while FDM predicts a single scale for core size which is determined by the particle mass. It can be understood by considering non-linear processes of mergers, the diversity could be generated. Mergers could also be responsible for structures at outer radii, such as the density profile proportional to the inverse cubic of the radius. In order to overcome the numerical difficulties and proceed, GPU-accelerated adaptive mesh code is now being intensively invented. We should see fantastic structures of FDM halos in the near future! Reported by Nagisa Hiroshima
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2023-02-16
Paper of the WeekWeek 3, February 2023
Title: Demographic history and species delimitation of three Zamia species (Zamiaceae) in south-eastern Mexico: Z. katzeriana is not a product of hybridization Author: José Said Gutiérrez-Ortega, Miguel Angel Pérez-Farrera, Sergio Lopez, Andrew P. Vovides Journal Reference: Botanical Journal of the Linnean Society, boac062 (2023) doi: https://doi.org/10.1093/botlinnean/boac062 Title: Perturbative analysis of the Wess-Zumino flow Author: Daisuke Kadoh, Kengo Kikuchi, Naoya Ukita arXiv: http://arxiv.org/abs/2302.06955v1 Title: BCS-BCS crossover between atomic and molecular superfluids in a Bose-Fermi mixture Author: Yixin Guo, Hiroyuki Tajima, Tetsuo Hatsuda, Haozhao Liang arXiv: http://arxiv.org/abs/2302.04617v1 Title: Doubly charmed tetraquark T^+_{cc} from Lattice QCD near Physical Point Author: Yan Lyu, Sinya Aoki, Takumi Doi, Tetsuo Hatsuda, Yoichi Ikeda, Jie Meng arXiv: http://arxiv.org/abs/2302.04505v1
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2023-02-16
Seminar Report
Quantum Matter Seminar by Dr. Chang Po-Yao on February 9, 2023
Please enter the seminar report here!On February 13, 2023, Assistant Professor Po-Yao Chang of the Department of Physics at National Tsing Hua University in Taiwan gave an online seminar entitled "Entanglement in non-Hermitian quantum systems and non-unitary conformal field theories." In the seminar, Professor Chang began by discussing the motivation for studying non-Hermitian systems, such as open quantum systems and those with imaginary self energy induced by interaction or disorder. He then introduced the basic concepts of entanglement entropy, arguing that while the quantity is defined through the ground state, it can be used to characterize the entire system similarly to how Boltzmann's thermal entropy characterizes a classical system. In particular, it can be used to characterize topological systems with anyons. Although general non-Hermitian systems have complex eigenvalues, he focused on systems that preserve parity and time-reversal (PT) symmetry, so that all of the eigenvalues must be real in order to determine the ground state and the entanglement entropy. He showed that in a non-Hermitian model, the entropy is negative and corresponds to the negative central charge, which uniquely characterizes conformal field theories (CFTs). As the main result of his recent work, Professor Chang proposed a generic entanglement entropy to characterize non-Hermitian systems and showed how it could be used to correctly obtain the entanglement properties of several non-Hermitian systems, such as the non-Hermitian Su-Schrieffer-Heeger (SSH) model, the q-deformed XXZ model with imaginary boundary terms, and the Affleck-Kennedy-Lieb-Tasaki (AKLT) model, using numerically extracted central charges. In conclusion, Professor Chang's seminar provided valuable insights into the field of entanglement in non-Hermitian quantum systems and non-unitary conformal field theories. The seminar was well-received by the audience, who appreciated the clarity of the presentation and the relevance of the research topic. Reported by Chen-Hsuan Hsu (Academia Sinica, Taiwan) and Ching-Kai Chiu
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2023-02-10
Seminar Report
Super smash problems workshop 3 on January 25-27, 2023
From January 25th to 27th, we organized the third Super Smash Problems (SSP) workshop in Kobe. This time we had Kyosuke Adachi (BDR/iTHEMS SPDR) presenting challenging problems he faced in his work. Two main topics were intensively discussed in the workshop. One of them was concerning the generalization of entropy-production in information thermodynamics. Entropy production can be regarded as a measure of irreversibility of stochastic processes. In other words, irreversibility necessarily comes with positive entropy production. We discussed various systems in biology, physics, and astrophysics that may be relevant to irreversible stochastic systems, like cell growth, formation of phylogenetic trees, machine-learning process, and how universe emerges. Second topic was about phase-separation. The theory of phase-separation has a rich mathematical structure: we explored methods with which we can computationally efficiently construct convex-hull of a given function. Also, because various systems exhibit phase-separation, we discussed the potential for which the method can be applied to other systems, including formation of stars. The three-day discussion did not allow us to reach solid conclusion though, we found it very fun and stimulating that mathematics can explain parts of our world that are seemingly totally different. We will continue discussing the problems and hopefully provide you all an update for something resulting. We the organizers sincerely appreciate the audience who attended Adachi-san’s introductory lecture and subsequent discussion; and of course, Adachi-san for the effort, time, and passion for the SSP workshop. We believe this was a short but very inspiring opportunity. Thank you so much! On behalf, Ryosuke Iritani Reported by Ryosuke Iritani
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2023-02-09
Paper of the WeekWeek 2, February 2023
Title: Brueckner G-matrix approach to two-dimensional Fermi gases with the finite-range attractive interaction Author: Hikaru Sakakibara, Hiroyuki Tajima, Haozhao Liang arXiv: http://arxiv.org/abs/2302.03446v1 Title: Nuclear response to dark matter signals in Ge and Xe odd-mass targets Author: M. M. Saez, O. Civitarese, T. Tarutina, K. Fushimi arXiv: http://arxiv.org/abs/2302.00879v1 Title: Robust Perfect Adaptation of Reaction Fluxes Ensured by Network Topology Author: Yuji Hirono, Hyukpyo Hong, Jae Kyoung Kim arXiv: http://arxiv.org/abs/2302.01270v1
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