News

45 news in 2023

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.
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
2023-03-23
Paper of the Week
Week 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
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.
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!
2023-03-16
Paper of the Week
Week 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
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.
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!
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.
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.
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.
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.
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.
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.
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
2023-03-09
Paper of the Week
Week 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
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
2023-03-03
Seminar Report
Quantum 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
2023-03-02
Paper of the Week
Week 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
2023-02-23
Paper of the Week
Week 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
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
2023-02-16
Paper of the Week
Week 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
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
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
2023-02-09
Paper of the Week
Week 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
2023-02-07
Person of the Week

Self-introduction: Christian Quirouette

Hi, my name is Christian Quirouette. I am a postdoctoral fellow at Toronto Metropolitan University in Canada. My field of research is virophyiscs, i.e. applying methods of physics to problems in virology. My research primarily focuses on stochastic mathematical modelling of viral infections. I’m excited to be working here at iTHEMS and have the chance to discuss and possibly collaborate with other researchers in other fields.
2023-02-06
Seminar Report

Early Universe Mini-workshop was held on Jan. 31 - Feb. 2, 2023

We held Early Universe Mini-workshop at SUURI-COOL (Kobe) on Jan. 31 - Feb. 2, 2023. The aim of the workshop was to gather researchers in cosmology and neighboring areas, from students to professors, and discuss future directions towards the understanding of the early Universe and related fundamental issues. In order to stimulate in-depth discussions and future collaborations, we organized the workshop in the way that the participants have ample time to interact with each other. Total 22 people attended the workshop on site, as well as over 30 people registered for online participation. The backgrounds of the participants were diverse in terms of nationality, gender and expertise. The topics of the talks at the workshop also range wide, albeit all on the early Universe cosmology in a broad sense, from observational aspects to formal ones. Reported by Ryo Namba
2023-02-03
Person of the Week

Self-introduction: Liang Zhang

I’m a Ph.D. student form Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences (CAS). And I came to iTHEMS on January 26th, 2023. When I was a undergraduate learning nuclear physics, I’m curious about how we can calculate the interactions between nucleons. I think it is the key for us to understand nucleus better. Beside this, I also learnt that there are hypernucleuses, where several nucleons are replaced by other baryons. So, if the interactions can be calculated from quark model and QCD theory, it allows us to study not only the normal nucleuses but also hypernucleuses which may exist at the beginning of the universe. HAL QCD is a great way to study the interactions between baryons by using lattice QCD calculation. I’m so glad to have this chance to study HAL QCD in iTHEMS. I hope I can receive knowledge and friendship here.
2023-02-02
Paper of the Week
Week 1, February 2023

Title: A Donaldson-Thomas crepant resolution conjecture on Calabi-Yau 4-folds Author: Yalong Cao, Martijn Kool, Sergej Monavari arXiv: http://arxiv.org/abs/2301.11629v1
2023-01-30
Book

Behavioral Ecology of Plants: their sensory system, communication, memory, and response

Editor: The Society for the Study of Species Biology Language: Japanese Ryosuke Iritani (Research Scientist, iTHEMS) is among the authors. How do plants perceive the world, and how do plants behave? This book is a compilation of the most recent plant environmental response research by up-and-coming scientists for beginners.
2023-01-25
Hot Topic

Farewell message from Dr. Shou Yoshikawa

Our colleague Shou Yoshikawa will move to the Tokyo Institute of Technology as an assistant professor from February 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Shou Yoshikawa: I spent almost a year at iTHEMS as an SPDR. I have had several opportunities to speak about my research at iTHEMS events and they have all been wonderful experiences. People from various fields actively asked me questions, which was a valuable experience. I would like to thank all the iTHEMS researchers and the iTHEMS desk staff for giving me a good environment in which I could concentrate on my research, even if it was only for a short time. I can fortunately continue to be a member of iTHEMS as a visiting scientist. I hope to get closer to more iTHEMS members in the future.
2023-01-25
Seminar Report

iTHEMS Colloquium by Dr. Gabriel Peyré on January 24, 2023

Prof. Gabriel Peyré, a CNRS research director and professor at Ecole Normale Supérieure (France) gave an iTHEMS-AIP joint colloquium entitled "Scaling Optimal Transport for High dimensional Learning" on January 24th. He started his talk with the old Monge's problem and moved to modern concept of the optimal transport by Kantorovich with historical stories behind it. He showed us that there have been many efforts of various mathematicians, economists, and physicists behind the developments of the optimal transport theory. In the later part of his talk, Prof. Gabriel Peyré focused on optimal transport problems in extremely high dimensions looking ahead various potential scientific applications like imaging, natural language processing, and biology. He introduced the key concept, entoropic term, with the historical quotation from Schrödinger, and showed us how it enables approximately solving optimal transport problems in high dimensions. He made his talk with a lot of beautiful figures and detailed explanations. We have many discussions during/after the talk, and enjoyed the colloquium. Reported by Akinori Tanaka
2023-01-24
Seminar Report
iTHEMS Math Seminar by Dr. Nobuo Iida on January 20, 2023

On January 20, Nobuo Iida from the Tokyo Institute of Technology gave a talk titled “Math and Physics of Seiberg-Witten theory” at the iTHEMS math seminar. He started by explaining a wide range of reviews in physics such as classical theory, relativity, quantum mechanics, and quantum field theory. Specially, these explanations were prepared for non-physicists and stimulated discussions. Also, his explanation of these theories contained many instructive examples of such theories which enable us to understand his talk easily. At the end of the first part, he focused on three kinds of QFTs: free theory, perturbative theory, and more general QFT, and introduced renormalization which gives interactions between high energy theory and low energy theory. Secondly, he started to explain general motivational questions in geometry on the mathematical side. This part is also prepared for non-mathematician. After reviewing the history of topology, he introduces Donaldson’s theory and Donaldson’s polynomial invariant, and Witten’s field-theoretic interpretation (topological twist of N=2 SUSY Yang-Mills theory) of the invariant. As the low energy effective theory of N=2 SUSY Yang-Mills theory, a family of gauge theories parametrized by so-called u-plane was introduced. By analyzing the family and using duality and topological twist, an idea of the Witten conjecture was shared, which relates Donaldson’s polynomial invariant with the Seiberg-Witten invariant on the mathematical side. His talk was very interesting and stimulated many questions and discussions. I believe it was a very worthwhile time for many participants. Reported by Masaki Taniguchi
2023-01-24
Book

Become a scientist who studies what you love !! [Chapter of Universe]

Cooperation / RIKEN Language: Japanese Five scientists explain the fascinating aspects of cutting-edge space research! Shigehiro Nagataki (Deputy Program Director, iTHEMS) and Naritaka Oshita (Special Postdoctoral Researcher, iTHEMS) are among the authors.
2023-01-20
Seminar Report

ABBL-iTHEMS Joint Astro Seminar by Dr. Nanae Domoto on January 20, 2023

Binary neutron star (NS) merger is a promising site for the rapid neutron capture nucleosynthesis (r-process). The radioactive decay of newly synthesized elements powers electromagnetic radiation, as called kilonova. The detection of gravitational wave from a NS merger GW170817 and the observation of the associated kilonova AT2017gfo have provided with us the evidence that r-process happens in the NS merger. However, the abundance pattern synthesized in this event, which is important to understand the origin of the r-process elements, is not yet clear. In this talk, Ms. Domoto first introduced an overview and current understanding of kilonova. Then, she discussed her recent findings of elemental features in photospheric spectra of kilonova toward identification of elements. Reported by Shigehiro Nagataki
2023-01-17
Seminar Report

ABBL-iTHEMS Joint Astro Seminar by Dr. Arno Vanthieghem on November 24, 2022

On November 24th, Dr. Arno Vanthieghem (Princeton University) gave a talk about the energy equipartition in Weibel-mediated shock waves. Shock waves relevant to astrophysical phenomena, such as supernovae and gamma-ray bursts, form via collective plasma processes. In the so-called collision-less shock waves, how exactly the different plasma species (thermal and suprathermal ions and electrons) share energy through dissipation is an open question. In the talk, he gave a broad overview and described the current understanding of this issue based on his recent studies. He carried out analytical kinetic estimates, semi-analytical Monte Carlo calculations, and ab-initio Particle-In-Cell simulations to tackle this issue in a wide range of shock velocities ranging from relativistic to non-relativistic regimes. In particular, he has introduced a theoretical model that can describe electron heating through the interplay between pitch-angle scattering in the microturbulence and the coherent electrostatic field induced by the difference in inertia between species. He has shown how successfully the model can be applied to unmagnetized shocks (shocks formed in a plasma without a background magnetic field). During and after the seminar, we had very fruitful discussions. We are grateful for the excellent talk and the great opportunity to have a face-to-face conversation with him. Reported by Hirotaka Ito
2023-01-16
Seminar Report
iTHEMS Biology Seminar by Dr. Tetsuya Kobayashi on September 8, 2022

On September 8th, I invited Dr. Testuya Kobayashi, and he talked about hessian geometric structure of equilibrium and nonequilibrium chemical reaction newtworks. He offered a topic on chemical reaction networks. He discussed central issues in biophysics and quantitative biology with recent work from their laboratory. This seminar had a special focus on researchers in the physical and mathematical sciences. However, it was also accessible to biological researchers. In particular, the discussion on the landscape was in line with each biological field. Reported by Daiki Kumakura
2023-01-16
Seminar Report
iTHEMS Biology Seminar by Mr. Daiki Kumakura on January 12, 2023

On January 12, I spoke about the basics of microbial ecology and the application of our field of research and life. First, I gave an introduction of where microbes can live. Then I talked about the application of enzymes of different microbes. And then, I talked about how to study microbiomes, especially metagenomic analysis. Finally, I talked about our project, the hot springs microbiome project. Our project is proceeding in several steps, so I talked about the perspective of our analysis. In this seminar, I focused on the researchers who are not familiar with microbial ecology. This allowed me to share my interest in microbial ecology. Reported by Daiki Kumakura
2023-01-16
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Conor Omand on December 20, 2022

Many energetic supernovae are thought to be powered by the rotational energy of a highly-magnetized, rapidly-rotating neutron star. The emission from the associated luminous pulsar wind nebula (PWN) can affect the system in different ways, including accelerating the ejecta, ionizing the ejecta, and breaking the spherical symmetry through hydrodynamic instabilities or large scale asymmetries. Modeling the observables from these processes; the light curves, spectrum, and polarization; is essential from understanding the nature of the central engine. Dr. Ommand presented the results of a radiative transfer study looking at the effects of a PWN on the supernova nebular spectrum, and the preliminary results from a more physically motivated light curve model for parameter inference, and a study examining the polarization that arises due to hydrodynamic instabilities in the ejecta of engine-driven supernovae. Reported by Shigehiro Nagataki
2023-01-16
Seminar Report

ABBL-iTHEMS Joint Astro Seminar by Dr. Shinya Wanajo on January 13, 2023

The discovery of an electromagnetic counterpart (kilonova) associated with GW170817 confirms that binary neutron star (NS) mergers are at least one of sites of r-process nucleosynthesis. However, there is no observational evidence that black hole (BH)-NS mergers are r-process sites. In this talk, Dr Wanajo overviewed the latest work of nucleosynthesis based on long-term hydrodynamics simulations of NS-NS and BH-NS mergers covering early dynamical and late post-merger mass ejections. Dr. Wanajo also briefly discussed a possible constraint on nuclear equations of state. Reported by Shigehiro Nagataki
2023-01-12
Paper of the Week
Week 3, January 2023

Title: Numerical studies on the finite-temperature CP restoration in 4D SU(N) gauge theory at $θ=π$ Author: Akira Matsumoto, Kohta Hatakeyama, Mitsuaki Hirasawa, Masazumi Honda, Jun Nishimura, Atis Yosprakob arXiv: http://arxiv.org/abs/2301.03879v1 Title: Spin conductivity spectrum and spin superfluidity in a binary Bose mixture Author: Yuta Sekino, Hiroyuki Tajima, Shun Uchino arXiv: http://arxiv.org/abs/2301.03031v1 Title: Apolipoprotein A1 and high-density lipoprotein limit low-density lipoprotein transcytosis by binding scavenger receptor B1 Author: Karen Fung, Tse Wing Winnie Ho, Zizhen Xu, Dante Neculai, Catherine A. A. Beauchemin, Warren L. Lee, Gregory D. Fairn doi: https://doi.org/10.1101/2022.08.08.503162 Title: Utility of Human In Vitro Data in Risk Assessments of Influenza A Virus Using the Ferret Model Author: Hannah M. Creager, Troy J. Kieran, Hui Zeng, Xiangjie Sun, Joanna A. Pulit-Penaloza, Katie E. Holmes, Anders F. Johnson, Terrence M. Tumpey, Taronna R. Maines, Catherine A. A. Beauchemin Journal Reference: Journal of Virology doi: https://doi.org/10.1128/jvi.01536-22
2023-01-07
Seminar Report
iTHEMS Biology Seminar by Dr. Yusuke Himeoka on November 17, 2022

On last November, Dr. Yusuke Himeoka at the University of Tokyo told us about a mysterious phenomena of bacterial cells, called "dormancy". The title of his talk was "Emergence of growth and dormancy from a kinetic model of the Escherichia coli central carbon metabolism". Starting from a network model of metabolism, he theoretically discussed how dormancy emerges at bacterial cells. During and after the talk, there were lively discussions. Thank you so much, Himeoka-san! Reported by Gen Kurosawa
2023-01-06
Seminar Report

iTHEMS Biology Seminar by Dr. Katsuhiko Sato on January 5, 2023

In iTHEMS biology seminar on January 5, Katsuhiko Sato (Hokkaido University) talked about a theoretical model of cell migration. First, he gave us the overview about cell migration. The dominant forces for the cell migrations are believed to the hydrostatic pressure in the cell, the contraction force by actomyosins and the frictions. Next, he constructed a mechanical model of the cell migration in an elegant manner. In this mechanical model, the cell migration dynamics is described by the balance between the energy and the dissipation. The dissipation describes the frictions. The energy includes the hydrostatic pressure, the contraction force, bending energy and the surface tension. Then, he introduced the cell polarization into the surface tension. By using this mechanical model, he demonstrated the unidirectional movement and the rotation of the cell cluster. We enjoyed the discussion with Sato-san on the detail of the modeling and its result. Thank you very much for a great talk, Sato-san! Reported by Hiroshi Yokota
2023-01-05
Paper of the Week
Week 2, January 2023

Title: Site-suitability difference and the expectation of species richness difference in stochastic two-subcommunity models Author: Ryosuke Iritani doi: https://doi.org/10.1101/2023.01.01.522407 Title: Clasper presentations of Habegger-Lin's action on string links Author: Yuka Kotorii, Atsuhiko Mizusawa arXiv: http://arxiv.org/abs/2212.14502v1
2023-01-04
Research News

RIKEN NEWS: The Power of Open Science to Defeat Pandemics

Catherine Beauchemin (Deputy Program Director, iTHEMS) is interviewed in the Winter issue of RIKEN NEWS 2023. COVID-19 can only transmit if an infected person infects an uninfected person. So if 100% of sick people stayed home, there would be zero new cases, and COVID-19 would be over. Since transmission relies on the behaviour of each individual, to manage or even end COVID-19 requires the cooperation of every person in society. This is the big challenge we continue to face even now. Misinformation has become a big problem in society. People trust their own opinion and that of their friends and family more than facts. There is also a tendency to distrust government officials, pharmaceutical companies, news media and scientists. Sometimes it is true that such people or organizations will lie or exaggerate, so it is reasonable and important for a person to be skeptical. In fact, skeptical thinking is essential in science: we need to open our mind to new results, especially those that contradict our assumptions and hypotheses. So what can be done? I think the best way to combat misinformation and build a lasting trust with the public is complete transparency, by openly (free/re-usable) sharing data and scientific analyses with the general public, so people around the world can independently verify the facts. To read more, please see the related link.

45 news in 2023