News

184 news in 2021

2021-10-22

Announcement

Prof. Motoko Kotani was elected as the next president of the International Science Council

Prof. Motoko Kotani (Senior Visiting Scientist, iTHEMS) was elected as the next President-elect of the International Science Council (ISC) at the ISC General Assembly held on October 14, 2012. The term of office is for three years starting in 2024. To read more, please see the related link (in Japanese).

2021-10-21

Paper of the Week

Week 4, October 2021

Title: Quiescent luminosities of transiently accreting neutron stars with neutrino heating due to charged pion decay Author: He-Lei Liu, Zi-Gao Dai, Guo-Liang Lv, Akira Dohi, Gao-Chan Yong, Masa-aki Hashimoto arXiv: http://arxiv.org/abs/2110.09729v1 Title: Prospects of fast flavor neutrino conversion in rotating core-collapse supernovae Author: Akira Harada, Hiroki Nagakura arXiv: http://arxiv.org/abs/2110.08291v1 Title: Involutions, knots, and Floer K-theory Author: Hokuto Konno, Jin Miyazawa, Masaki Taniguchi arXiv: http://arxiv.org/abs/2110.09258v1

2021-10-21

Event Schedule

Events for the 5th week of October 2021

Tuesday, October 26, 10:00- Conference: Can social issues be solved by mathematical science? -attempts and challenges Thursday, October 28, 15:00- iTHEMS Colloquium Friday, October 29, 12:30- Coffee Meeting

2021-10-20

Press Release

Increased number of drought-responsive genes in a tropical rainforest tree, Shorea leprosula (Dipterocarpaceae)

A collaborative research group including Dr. Jeffrey Fawcett (Senior Research Scientist, iTHEMS) has sequenced the genome of a tropical tree species, Shorea leprosula (Dipterocarpaceae), which is important for the global environment and as an imported timber. Although the trees grow in tropical East Asia, which is blessed with abundant rainfall, they unexpectedly showed an increase in drought-responsive genes, revealing the importance of rare droughts in the tropics. Global environmental change is exacerbating large-scale drought associated with El Niño Southern Oscillations (ENSO) in the tropics, and it is expected that the results of this study will be applied toward sustainable forestry and tropical rainforest conservation. For more information, please visit the Yokohama City University website.

2021-10-19

Seminar Report

Quantum Matter SG seminar by Mr. Seishiro Ono on October 12, 2021

Quantum Matter Study Group invited Seishiro Ono from the University of Tokyo to give a talk about symmetry indicators for topological (nodal) superconductors. First, he gave a review of symmetry indicators for topological insulators. In condensed matter physics, using topological invariants to search for topological materials is difficult; alternatively, symmetry indicators serve a simpler calculation to identify topological states of matter since this method considers the properties located at symmetry invariant momenta. After the introduction, the speaker extended the indicator approach to topological (nodal) superconductors. Although the different types of superconducting pairings lead to complications in the symmetry-based classification, the speaker showed that their work classifies all the (magnetic) space groups with possible superconducting pairings. Furthermore, he demonstrated their own database server listing all the classification of the topological superconductors by using the approach of symmetry indicators. The work serves as an important guide for hunting topological superconductors. Reported by Ching-Kai Chiu

2021-10-18

Seminar Report

ABBL/iTHEMS Astro Seminar by Dr. Nobuya Nishimura on October 15, 2021

At the seminar, there were lots of questions and answers for r-process nucleosynthesis and kilonova events. The speaker presented lots of his excellent works on them, and the audience enjoyed his presentation with curiosity. Reported by Shigehiro Nagataki

2021-10-14

Paper of the Week

Week 3, October 2021

Title: The genome of Shorea leprosula (Dipterocarpaceae) highlights the ecological relevance of drought in aseasonal tropical rainforests Author: Kevin Kit Siong Ng, Masaki J. Kobayashi, Jeffrey A. Fawcett, Masaomi Hatakeyama, Timothy Paape, Chin Hong Ng, Choon Cheng Ang, Lee Hong Tnah, Chai Ting Lee, Tomoaki Nishiyama, Jun Sese, Michael J. O’Brien, Dario Copetti, Mohd Noor Mat Isa, Robert Cyril Ong, Mahardika Putra, Iskandar Z. Siregar, Sapto Indrioko, Yoshiko Kosugi, Ayako Izuno, Yuji Isagi, Soon Leong Lee, Kentaro K. Shimizu Journal Reference: Commun Biol 4, 1166 (2021) doi: https://doi.org/10.1038/s42003-021-02682-1 Title: Effect of advancing age on the reproductive performance of Japanese Thoroughbred broodmares Author: Jeffrey A. FAWCETT, Hideki INNAN, Takeru TSUCHIYA, Fumio SATO Journal Reference: J. Equine Sci. Vol. 32, No. 2, pp. 31–37 (2021) doi: https://doi.org/10.1294/jes.32.31 Title: Universal relation for supernova gravitational waves Author: Hajime Sotani, Tomoya Takiwaki, Hajime Togashi arXiv: http://arxiv.org/abs/2110.03131v2 Title: Topology and symmetry of circular photogalvanic effect in the chiral multifold semimetals: a review Author: Congcong Le, Yan Sun doi: https://doi.org/10.1088/1361-648X/ac2928 arXiv: http://arxiv.org/abs/2110.03434v1

2021-10-13

Award

Nagisa Hiroshima received the Award for Female Researchers of the University of Toyama

University of Toyama has announced that Nagisa Hiroshima (Visiting Scientist, iTHEMS) received "The Award for Female Researchers of the University of Toyama". Congratulations!

2021-10-13

Person of the Week

Self-introduction:Gilberto Nakamura

My name is Gilberto Nakamura and I joined iTHEMS as a postdoctoral researcher in Oct 2021, after working as a postdoctoral fellow at IJCLab/CNRS in France. I'm interested on the role of noise and correlations in biologically inspired systems. The relation between fluctuations and correlations lies at the heart of the theory of critical phenomena, with ramifications in Statistical Physics and Quantum Field Theory. Fluctuations in biological systems are further exacerbated by the innate variability of organisms, adding richness to the dynamics and promoting the emergence of complex behavior. More recently, I have worked on disease-spreading dynamics, viral infections, and migration of cancer cells, all of which have a significant impact on human health and require continued interdisciplinary efforts across Mathematics, Physics, and Biology. My current focus has been on bottom-up approaches, starting from microscopic stochastic models and working them out into the hydrodynamic limit, with support from numerical Monte Carlo simulations, followed by parameter extraction from data. I am sure the interdisciplinary environment fostered by iTHEMS will promote new collaborations and further advance my research goals.

2021-10-12

Seminar Report

Quantum Matter SG seminar by Prof. Bohm-Jung Yang on October 7, 2021

The Quantum Matter study group had the honor to invite Prof. Bohm-Jung Yang to give a talk on October 7th. He talked about wave function geometry and anomalous Landau levels of flat bands. He started with a heuristic introduction by explaining the geometry matters in a flat band, including the notion of the (Hilbert-Schmidt) quantum distance and the quantum metric. Particularly, he used a Kagome lattice as an example of the singular touching point of the flat band and quadratic band locked by the geometry. Furthermore, in the presence of a magnetic field, the singular flat band evolves into very dense anomalous Landau levels. Remarkably, the relation between the Landau level spreading and the maximum of the quantum distance can be described by a universal formula, independent of material parameters. In consequence, deducing the Landau level spreading in (spectroscopic) experiments would allow for the measurement of the quantum distance, thus probing the quantum geometry of the wave functions. The study was extended to the (spin-orbit-coupled) Lieb lattice with one flat band sandwiched by two dispersive bands. In this case, the Landau level spreading of the isolated flat band is determined by the fidelity tensor. This talk showed us the interesting and subtle interplay between the band flatness and the Landau levels. Reported by Ching-Kai Chiu and Chen-Hsuan Hsu

2021-10-11

Seminar Report

iTHEMS Theoretical Physics Seminar by Prof. Keisuke Izumi on September 13, 2021

At the seminar organized by the iTHEMS-physics study group, Prof. Keisuke Izumi discussed the S-matrix unitarity toward UV completion. Einstein gravity is not renormalizable and does not hold perturbative unitarity at high energy. This is the main reason why the construction of quantum gravity is difficult. A conjecture was proposed by Llewellyn Smith, "renormalizablility and tree-unitarity at high energy give the same conditions". This conjecture would be important because it shows that, if a theory is constructed such that unitarity is satisfied, renormalizablility holds automatically, and vice versa. Unfortunately, a counterexample was pointed out. If a theory involves higher derivatives, there exists a theory which is renormalizable but does not satisfy tree-unitarity. A candidate of quantum gravity, the quadratic gravity (R_{\mu\nu}^2 gravity), is one of the examples. Therefore, Llewellyn Smith's conjecture would not be useful for the discussion of quantum gravity. Then, Prof. Izumi and his collaborators introduced a new conjecture, "renormalizablility and S-matrix unitarity (or often called pseudo-unitarity) at high energy give the same conditions". In his talk, Prof. Izumi explained Llewellyn Smith's conjecture and his contribution to it. Then, he introduced his new conjecture. Finally, he showed that his conjecture works well even in theories with higher derivatives. Reported by Ryo Namba

2021-10-07

Paper of the Week

Week 2, October 2021

Title: Confinement/deconfinement transition in the D0-brane matrix model -- A signature of M-theory? Author: Georg Bergner, Norbert Bodendorfer, Masanori Hanada, Stratos Pateloudis, Enrico Rinaldi, Andreas Schäfer, Pavlos Vranas, Hiromasa Watanabe arXiv: http://arxiv.org/abs/2110.01312v1 Title: Searching for TeV gamma-ray emission from SGR\,1935+2154 during its 2020 X-ray and radio bursting phase Author: H.E.S.S. Collaboration (Naomi Tsuji) Journal Reference: ApJ 919, 106-114 (2021) doi: https://doi.org/10.3847/1538-4357/ac0fe1 arXiv: http://arxiv.org/abs/2110.00636v1 Title: Heavy-quark spin polarization induced by Kondo effect under magnetic field Author: Daiki Suenaga, Yasufumi Araki, Kei Suzuki, Shigehiro Yasui arXiv: http://arxiv.org/abs/2109.14799v1 Title: Yu-Shiba-Rusinov states in a superconductor with topological Z2 bands Author: Ching-Kai Chiu, Ziqiang Wang arXiv: http://arxiv.org/abs/2109.15227v1 Title: Design strong anomalous Hall effect via spin canting in antiferromagnetic nodal line materials Author: Congcong Le, Claudia Felser, Yan Sun Journal Reference: PhysRevB.104.125145(2021) doi: https://doi.org/10.1103/PhysRevB.104.125145 arXiv: http://arxiv.org/abs/2105.09237v1

2021-10-07

Event Schedule

Events for the 3rd week of October 2021

Tuesday, October 12, 16:00- Quantum Matter Seminar Friday, October 15, 12:30- Coffee Meeting

2021-10-04

Person of the Week

Self-introduction:Yixin Guo

My name is Yixin GUO, a Junior Research Associate joined in iTHEMS from October 2021. I come from China, and now study in the Doctoral Course at The University of Tokyo. I am majoring in theoretical nuclear physics. I am mainly interested in (but not only) the quantum many-body problem, nuclear structure theory, density functional theory, and nuclear reaction theory. I also have some experience in the accelerator physics. I look forward to exchanging ideas with various researchers from different fields.

2021-09-30

Paper of the Week

Week 5, September 2021

Title: Observation of the gamma-ray binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS telescopes Author: C. B. Adams, et al. (N. Tsuji) arXiv: http://arxiv.org/abs/2109.11894v1 Title: Design strong anomalous Hall effect via spin canting in antiferromagnetic nodal line materials Author: Congcong Le, Claudia Felser, Yan Sun Journal Reference: PhysRevB.104.125145(2021) doi: https://doi.org/10.1103/PhysRevB.104.125145 arXiv: http://arxiv.org/abs/2105.09237v1

2021-09-29

Seminar Report

Report of iTHEMS colloquium - Finding Gravitational Waves from the Early Universe

Prof. Eiichiro Komatsu, a director at the Max Planck Institute for Astrophysics (Germany), shared his enthusiasm for observational aspects of cosmology and in particular the primordial gravitational waves (GWs) generated during the earliest stage of our Universe, called cosmic inflation. Such GWs distort the space while propagating and leave footprints as the polarizations of the cosmic microwave background (CMB) and as a more direct signal at the GW interferometers. As a world-leading expert on all areas of cosmology, Prof. Komatsu explained the fundamental aspects of CMB and GW observations and their implications in understanding the physics of the primordial Universe (from his remark, "We all came from quantum fluctuations"). He made his talk visually accessible to non-experts while providing fresh interpretations of the data in cosmological observations. He also clarified the importance and excitement of the upcoming LiteBIRD project, the first CMB mission led by Japan, which expects its launch toward the end of 2020's. After the official part of his talk, he remained to be available for both scientific and non-scientific discussions with the audience in an informal setting and exchanged more technically involved thoughts as well as his everyday-life experiences. Reported by Ryo Namba

2021-09-23

Event Schedule

Events for the 5th week of September 2021

Monday, September 27, 16:00- iTHEMS Colloquium Friday, October 1, 12:30- Coffee Meeting

2021-09-23

Paper of the Week

Week 4, September 2021

Title: On the ease of excitation of black hole ringing: Quantifying the importance of overtones by the excitation factors Author: Naritaka Oshita arXiv: http://arxiv.org/abs/2109.09757v1 Title: Effective field theory of fluctuating wall in open systems: from a kink in Josephson junction to general domain wall Author: Keisuke Fujii, Masaru Hongo arXiv: http://arxiv.org/abs/2109.10335v1 Title: Persistence of cluster structure in the ground state of $^{11}$B Author: Naoyuki Itagaki, Tomoya Naito, Yuichi Hirata arXiv: http://arxiv.org/abs/2109.09957v1 Title: High-dimensional structure learning of sparse vector autoregressive models using fractional marginal pseudo-likelihood Author: Kimmo Suotsalo, Yingying Xu, Jukka Corander, Johan Pensar Journal Reference: Stat Comput 31, 73 (2021) doi: https://doi.org/10.1007/s11222-021-10049-z arXiv: http://arxiv.org/abs/2011.01484v1 Title: Principal-Axis Analysis of the Eddington Tensor for the Early Post-Bounce Phase of Rotational Core-Collapse Supernovae Author: Wakana Iwakami, Akira Harada, Hiroki Nagakura, Ryuichiro Akaho, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, Kohsuke Sumiyoshi, Shoichi Yamada arXiv: http://arxiv.org/abs/2109.05846v2 Title: Universal relations between the quasinormal modes of neutron star and tidal deformability Author: Hajime Sotani, Bharat Kumar arXiv: http://arxiv.org/abs/2109.08145v1 Title: A semi-analytic afterglow with thermal electrons and synchrotron self-Compton emission Author: Donald C. Warren, Maria Dainotti, Maxim V. Barkov, Bjorn Ahlgren, Hirotaka Ito, Shigehiro Nagataki arXiv: http://arxiv.org/abs/2109.07687v1 Title: Derivative expansion in the HAL QCD method for a separable potential Author: Sinya Aoki, Koichi Yazaki arXiv: http://arxiv.org/abs/2109.07665v1

2021-09-22

Hot Topic

Mathematics and Physics: Topology, Insulators and My Research Life

Dr. Tomoki Ozawa (Visiting Scientist, iTHEMS) writes on the website "SURI-JOSHI" about topological insulators and his research life and daily life. Please see the related link for the article.

2021-09-17

Seminar Report

NEW WG Seminar by Prof. Yuta Murakami on September 15, 2021

Yuta Murakami from Tokyo Institute of Technology told us about "High-harmonic generation in strongly correlated systems." High-harmonic generation (HHG) by strong AC electric fields is one of the hottest topics in cond-mat physics. After a brief overview of HHG in various materials such as gasses and semi-conductors and also recent experimental results in Mott insulators, Yuta explained his recent numerical studies on HHG in strongly correlated systems and clarified unique features of HHG arising from the strongly-correlated nature. About 30 people joined the seminar and we enjoyed fruitful discussions during and after the seminar. Reported by Hidetoshi Taya

2021-09-17

Seminar Report

NEW WG Seminar by Prof. Matteo Baggioli on September 10, 2021

Matteo Baggioli (Jiao-Tong U. Shanghai) gave a talk on "Towards a description of amorphous solids and viscoelastic materials using effective field theory and holographic methods." Amorphous and viscoelastic materials appear in many places, not only in scientific problems but also in our daily life. Despite its ubiquity, there are many intriguing phenomena that are not yet understood, in particular, in the non-linear regime. In the talk, Matteo explained his recent attempts to formulate non-linear responses in amorphous and viscoelastic materials based on holographic and effective-field-theory techniques. Matteo also discussed open problems and future directions that we can pursue in the future. There were about 30 participants from various fields of physics, and we had fruitful discussions from a broad point of view during and even after the talk. Reported by Hidetoshi Taya

2021-09-17

Research News

A New Mechanism to Explain Multispecies Coexistence in Plants - Evolutionary Rescue Caused by the Evolution of Self-Fertilization before Flowering

Koki Katsuhara (Assistant Professor, Okayama University; at the time: Kobe University), Yuuya Tachiki (Assistant Professor, Tokyo Metropolitan University), Ryosuke Iritani (Research Scientist, iTHEMS; at the time: University of California, Berkeley, University of Exeter) and Atsushi Ushimaru (Professor, Kobe University) performed simulations using an individual-based model and found that in two plant species that share the same species of pollinator and are in competition, evolutionary rescue occurs in which the evolution of higher self-fertilization rates in the rarer species results in an increase in population size, thereby promoting long-term coexistence between the two species. The results of this study add a new theory to explain why multiple flowering species can coexist in the same place, and also provide a new perspective for the evolution of diverse reproductive strategies in plants. Understanding the mechanisms that create and maintain plant diversity, which supports the basis of terrestrial ecosystems, is essential not only for understanding the origin of biodiversity, but also for forming a sustainable society in harmony with ecosystems, and is an important knowledge in both basic and applied aspects. For more information, please visit the Okayama University website at the related link.

2021-09-16

Paper of the Week

Week 3, September 2021

Title: Equation of state of neutron star matter and its warm extension with an interacting hadron resonance gas Author: Yuki Fujimoto, Kenji Fukushima, Yoshimasa Hidaka, Atsuki Hiraguchi, Kei Iida arXiv: http://arxiv.org/abs/2109.06799v1

2021-09-09

Event Schedule

Events for the 3rd week of September 2021

Monday, September 13, 13:30- iTHEMS Theoretical Physics Seminar Tuesday, September 14, 9:30- DMWG Seminar Wednesday, September 15, 13:30- NEW WG Seminar Friday, September 17, 12:30- Coffee Meeting

2021-09-09

Paper of the Week

Week 2, September 2021

Title: Subregion Spectrum Form Factor via Pseudo Entropy Author: Kanato Goto, Masahiro Nozaki, Kotaro Tamaoka arXiv: http://arxiv.org/abs/2109.00372v1

2021-09-09

Seminar Report

iTHEMS Biology Seminar by Dr. Euki Yazaki on September 9, 2021

Molecular phylogenetic analysis is one of the most important analysis methods in biology. If used well, it can help us understand how organisms diversified and how genes evolved. The methods of molecular phylogenetic analysis are subject to debate, so we are familiar with the mathematical background. However, we are not so familiar with how the data sets for phylogenetic analysis are made up. In this Biology Seminar, the main alignment algorithms for making data sets were explained and discussed. Scoring is important in alignment algorithms, and there was a discussion on scoring for amino acid and nucleic acid mutations and scoring for gap penalties. The discussion on alignment distance was also heated. I hope the audience all enjoyed it. I would like to have another discussion on phylogenetic analysis and mathematical background next time. Thank you very much!

2021-09-09

Seminar Report

ABBL-iTHEMS Joint Seminar by Dr. Yosuke Mizuno on September 3, 2021

Prof. Yosuke Mizuno (Tsung-Dao Lee Institute, Shanghai JiaoTong University) gave an excellent talk on "The Polarised ring ofthe Supermassive Black Hole in M87: EHT observations andtheoretical modeling". He introduced that the Event HorizonTelescope (EHT) had mapped the central compact radio source of theelliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Recently EHT provided new images of the polarised emissionaround the central black hole in M87 on event-horizon scale. Thispolarised synchrotron emission probes the structure of magnetic fieldsand the plasma properties near the black hole. He and hiscollaborators found that the net azimuthal linear polarisationpattern may result from organised, poloidal magnetic fields in the emission region. In a quantitative comparison with a large simulated polarimetric image library, he found that magnetically arrested accretion disks are favoured to explain polarimetric EHT observations. In this talk, he also discussed about a new modelling study of M87jets in the collimation and acceleration region. Reported by Shigehiro Nagataki

2021-09-08

Person of the Week

Self-introduction: Matthias Berwein

My name is Matthias Berwein and I'm from Germany. I did my undergraduate studies in physics at TU Munich from 2006 to 2011, followed by a PhD 2012-2016 also at TU Munich in the group of Nora Brambilla. Then I came to Japan for my first postdoc at Tohoku University in Sendai under a JSPS fellowship with Yukinari Sumino. Since 2018 I've been at RIKEN, first in the SPDR program at Quantum Hadron Physics Lab, and from 2021 in iTHEMS. The focus of my research lies in theoretical studies of the strong interactions through the theory of quantum chromodynamics and with a special emphasis on heavy quarks. I have worked on several projects on the static quark potential, heavy quarkonium hybrids, and heavy quarks at finite temperature, using perturbative calculations and effective theory methods. Currently, I'm studying properties of the energy-momentum tensor in these environments. I look forward to many fruitful interactions with fellow researchers here at iTHEMS.

2021-09-03

Seminar Report

Quantum Matter SG seminar by Dr. Levente Rózsa on September 1, 2021

Dr. Levente Rózsa gave a talk about Yu-Shiba-Rusinov (YSR) states and other localized states appearing in superconductors for Quantum Matter Study Group on September 1st, 2021. There are three distinct types of localized in-gap states in superconductors —- Majorana bound states, YSR states, and Caroli-de Genne-Matricon states. Dr. Rózsa first introduced Majorana bound states emerging in topological superconductors. Next, he talked about the anisotropic spacial distribution of the YSR states on the La surface (0001). The YSR state is a localized in-gap state induced by magnetic impurity in a superconductor. He showed that this anisotropy stems from the anisotropic Fermi surface. Furthermore, he discussed the localized states appearing in vortex cores are Caroli-de Genne-Matricon states, instead of Majorana bound states. He went through the experimental details and compared them with his theoretical simulation. The talk was well-organized and clear. We thank Dr. Rózsa for sharing his interesting research works. Reported by Ching-Kai Chiu and Thore Posske

2021-09-03

Seminar Report

iTHEMS Biology Seminar by Dr. Yingying Xu on September 2, 2021

In today's Biology Seminar, Yingying Xu (iTHEMS) introduced one paper arguing the quantitative explanation for immune-escape of virus by means of quasispecies dynamics models with Gillespie algorithm. She firstly explained the background information about the immune systems. She then taught us how the authors simulated the dynamics and made a comparison with experimental data. We finally discussed potential future directions to further development of quantitative modeling of chronic or acute infectious virus, highlighting a potential issue in estimating the mutation rate of virus. We learned a lot from this journal club, thank you so much for the great talk, Yingying! Reported by Ryosuke Iritani

2021-09-02

Paper of the Week

Week 1, September 2021

Title: Anomaly-induced edge currents in hydrodynamics with parity anomaly Author: Takuya Furusawa, Masaru Hongo arXiv: http://arxiv.org/abs/2108.12192v1 Title: Near-threshold Spectrum from Uniformized Mittag-Leffler Expansion -Pole Structure of $Z(3900)$- Author: Wren A. Yamada, Osamu Morimatsu, Toru Sato, Koichi Yazaki arXiv: http://arxiv.org/abs/2108.11605v1 Title: Subregion Spectrum Form Factor via Pseudo Entropy Author: Kanato Goto, Masahiro Nozaki, Kotaro Tamaoka arXiv: http://arxiv.org/abs/2109.00372v1

2021-09-02

Event Schedule

Events for the 2nd week of September 2021

Friday, September 10, 12:30- Coffee Meeting Friday, September 10, 13:30- NEW WG Seminar

2021-08-31

Press Release

Supercomputer Predicts Fascinating New Particle Charmed Di-Omega - A new page toward solving the puzzle of the 6-quark states has been added -

An international collaboration including Takuya Sugiura (Postdoctoral Researcher, iTHEMS) , Tetsuo Hatsuda (Program Director, iTHEMS), and Takumi Doi (Senior Research Scientist, Quantum Hadron Physics Laboratory, RNC) has theoretically predicted the existence of a new particle called Charmed Di-Omega which consists of six charm quarks. To read more, please see the related link (in Japanese).

2021-08-30

Seminar Report

iTHEMS Biology Seminar by Dr. Gen Kurosawa on August 26, 2021

During this covid-19 crisis, we check our body temperature (Tb) every day since Tb is essential variable of our body. In fact, some organisms like humans try to keep Tb constant, but some other organisms chose completely different strategies, including hibernation (冬眠). On August 26, I talked about hibernation at the iTHEMS Biology Seminar. Hibernation is a strategy for the organisms, including a primate to survive in a severe season with limited food and water availability. Although there have been a lot of studies about hibernation since the era of Aristotle, fundamental problems of hibernation remain unknown. Recently, we started to investigate mathematically body temperature profile of hibernating hamsters. During hibernation, the organisms drastically decrease their basal metabolisms, drop their body temperature (Tb) more than 10 degree, and become immobile. Mysteriously, Tb during hibernation does not remain constant at very low value, but greatly fluctuates with inconstant period of several days. At the seminar, I showed that a simple model can reproduce well and forecast Tb data during hibernation. Thankfully, there were a lot of questions and suggestions about the method of time-series analysis, hibernating species, and so on which are precious to me. This study is the collaboration with Prof. Yoshifumi Yamaguchi at Institute of Low Temperature Science, Hokkaido Univ and Shingo Gibo at iTHEMS. I’m really enjoying this research. I am happy if the audiences enjoyed the seminar and forgot about the heat. Thanks!

2021-08-27

Hot Topic

RIKEN-Vancouver Joint Workshop on Quantum Computing was held on August 24-25, 2021

RIKEN-Vancouver Joint Workshop on Quantum Computing was held online on August 24-25. The main aim of this workshop is that the quantum people in RIKEN (iTHEMS and RQC) and Vancouver (Quantum BC) get together online to discuss scientific activities and explore future collaborations. There were altogether 164 registrations (90 from Japan, 62 from Canada and 12 from other countries). 12 scientific talks were presented together with 3 introduction to iTHEMS, RQC and Quantum BC. From iTHEMS, Jason Chang, Etsuko Itou, and Takumi Doi gave talks respectively on the Schroedinger equation, the U(1) gauge theory and combinatorial optimization. After each session, there were one-hour breakout sessions, so that people can ask further questions to the speakers, which worked very well. The workshop was an excellent first step toward a close tie between RIKEN quantum activities and Vancouver quantum activities.

2021-08-26

Paper of the Week

Week 5, August 2021

Title: Intraspecific Adaptation Load: A Mechanism for Species Coexistence Author: Masato Yamamichi, Daisuke Kyogoku, Ryosuke Iritani, Kazuya Kobayashi, Yuma Takahashi, Kaori Tsurui-Sato, Akira Yamawo, Shigeto Dobata, Kazuki Tsuji, Michio Kondoh Journal Reference: Trends in Ecology & Evolution 35(10), 897-907 (2020) doi: https://doi.org/10.1016/j.tree.2020.05.011 Title: Reproductive interference hampers species coexistence despite conspecific sperm precedence Author: Ryosuke Iritani, Suzuki Noriyuki Journal Reference: Ecology and Evolution 11(5),1957-1969 (2021) doi: https://doi.org/10.1002/ece3.7166 Title: Temporal changes in spatial variation: partitioning the extinction and colonisation components of beta diversity Author: Shinichi Tatsumi, Ryosuke Iritani, Marc W. Cadotte Journal Reference: Ecology Letters 24(5), 1063-1072 (2021) doi: https://doi.org/10.1111/ele.13720 Title: A solution to a sex ratio puzzle in Melittobia wasps Author: Jun Abe, Ryosuke Iritani, Koji Tsuchida, Yoshitaka Kamimura, Stuart A. West Journal Reference: PNAS 118 (20) e2024656118 (2021) doi: https://doi.org/10.1073/pnas.2024656118 Title: Cooperative interactions among females can lead to even more extraordinary sex ratios Author: Ryosuke Iritani, Stuart A. West, Jun Abe Journal Reference: Evolution Letters 5(4),370-384 (2021) doi: https://doi.org/10.1002/evl3.217 Title: Construction of energy density functional for arbitrary spin polarization using functional renormalization group Author: Takeru Yokota, Tomoya Naito arXiv: http://arxiv.org/abs/2108.10787v1 Title: Femtoscopic study of coupled-channel $NΞ$ and $ΛΛ$ interactions Author: Y. Kamiya, K. Sasaki, T. Fukui, T. Hyodo, K. Morita, K. Ogata, A. Ohnishi, T. Hatsuda arXiv: http://arxiv.org/abs/2108.09644v1 Title: Product of Random States and Spatial (Half-)Wormholes Author: Kanato Goto, Yuya Kusuki, Kotaro Tamaoka, Tomonori Ugajin arXiv: http://arxiv.org/abs/2108.08308v1 Title: Band width and the Rosenberg index Author: Yosuke Kubota arXiv: http://arxiv.org/abs/2108.08506v1

2021-08-25

Seminar Report

iTHEMS Biology Seminar by Dr. Naohiro Kawamoto on August 19, 2021

In iTHEMS Biology Seminar on August 19th, Dr. Naohiro Kawamoto (Osaka University) gave a talk on cyanobacterial circadian oscillations. It is known that three proteins (KaiA, KaiB and KaiC) are sufficient for generating self-sustained circadian oscillations in cyanobacterium. In this talk, Dr. Kawamoto experimentally showed that the lack of kaiA causes damped oscillation. Then, he analyzed the benefit of the damped circadian oscillation by using a simple mathematical model of the interaction between the damped and self-sustained oscillators. This analysis revealed that kaiA-less damped oscillator can resonate to another oscillatory process. Finally, he talked about evolution of related to evolution of circadian clock system for future work. After the talk, we enjoyed discussion about mathematical modeling of various types of coupled oscillators. Thank you very much, Naohiro! Reported by Shingo Gibo

2021-08-25

Seminar Report

Quantum Matter SG seminar by Prof. Daw-Wei Wang on August 23, 2021

On August 23rd, 2021, Quantum Matter Study Group invited Prof. Daw-Wei Wang to give a talk on the application of machine learning in condensed matter physics. First, he briefly introduced learning and emphasized using supervised machine learning in condensed matter physics. The practical condensed matter problem he focused on is the physics of many-body systems since the many-body problem is challenging to solve. By randomly choosing small portions of a many-body Hamiltonian, machine learning can almost accurately predict the energy of the many-body system. Prof. Wang used the 1D Fermi-Hubbard model and the 1D Ising model to show the consistency between the learning prediction and the known solutions. The limitation of this approach is that the system size has to be fixed. To resolve this problem, he used the transfer learning approach to extend the prediction to a larger system size by learning from small systems. In the end, he talked about identifying the topological phase transition points by improving the machine learning approach in the literature. The talk is very comprehensive and informative. We thank Prof. Wang for giving a wonderful talk. Reported by Ching-Kai Chiu

2021-08-23

Hot Topic

Nihon Keizai Shimbun: Utilizing the Power of Quantum Computers in Combination

Dr. Hirotaka Irie (iTHEMS Visiting Scientist (Industry)) was interviewed in the Nihon Keizai Shimbun. He talks about the "hybrid type" that combines the best parts of conventional computers and quantum computers. Please see the related link for details.

2021-08-19

Event Schedule

Events for the 4th week of August 2021

Monday, August 23, 16:00- Quantum Matter Seminar Tuesday, August 24-25, RIKEN-Vancouver Joint Workshop on Quantum Computing Friday, August 27, 12:30- Coffee Meeting

2021-08-19

Paper of the Week

Week 4, August 2021

Title: Observing Supernova Neutrino Light Curves with Super-Kamiokande: II. Impact of the Nuclear Equation of State Author: Ken'ichiro Nakazato, Fumi Nakanishi, Masayuki Harada, Yusuke Koshio, Yudai Suwa, Kohsuke Sumiyoshi, Akira Harada, Masamitsu Mori, Roger A. Wendell arXiv: http://arxiv.org/abs/2108.03009v1 Title: The generalized Nielsen-Ninomiya Theorem for the 17 wallpaper: Classification of 2D nodal superconductors, Dirac semimetals, and non-Hermitian nodal systems Author: Congcong Le, Zhesen Yang, Fan Cui, A. P. Schnyder, Ching-Kai Chiu arXiv: http://arxiv.org/abs/2108.04534v1 Title: Matrix Model simulations using Quantum Computing, Deep Learning, and Lattice Monte Carlo Author: Enrico Rinaldi, Xizhi Han, Mohammad Hassan, Yuan Feng, Franco Nori, Michael McGuigan, Masanori Hanada arXiv: http://arxiv.org/abs/2108.02942v1 Title: Universality of Interior Metric of Typical Black Holes Author: Hikaru Kawai, Yuki Yokokura arXiv: http://arxiv.org/abs/2108.02242v2 Title: Stability of the protoneutron stars toward black hole formation Author: Hajime Sotani, Kohsuke Sumiyoshi arXiv: http://arxiv.org/abs/2108.02484v1

2021-08-18

Seminar Report

iTHEMS Math Seminar by Dr. Yalong Cao on August 6, 2021

The final Math Seminar of this semester was held on August 9th. This time, we invited our new colleague Dr. Yalong Cao as a speaker. First, he gave an overview of the celebrated Yang-MIlls theory in real dimensions 3 and 4. Next, it was explained that one can complexify the above Yang-Mills theory on Calabi-Yau 3 and 4-folds. The point is that in algebro-geometric setting, moduli spaces of Yang-Mills connections admit nice compactifications. Finally, he explained the connection between the above story and the enumerative geometry, specifically on counting (stable) coherent sheaves and complex ASD connections on Calabi-Yau 4-folds. He and his collaborators proposed a conjectural sheaf-theoretic interpretation of Klemm-Pandharipande’s BPS invariants of CY 4-folds defined using Gromov-Witten theory. Reported by Hiroyasu Miyazaki

2021-08-17

Seminar Report

iTHEMS Theoretical Physics Seminar by Dr. Shunichiro Kinoshita on August 16, 2021

Shunichiro Kinoshita (Chuo U.) gave a talk on "Application of AdS/CFT to non-equilibrium phenomena in external electric fields. "After a brief introduction to the AdS/CFT correspondence, Shunichiro analyzed a holographic QCD system under strong electric fields constructed with D3/D7 branes. Shunichiro considered two kinds of electric-field configurations.The first one was a field with a sudden switching on (quenched setup). Shunichiro discussed how the confinement-deconfinement phase transition occurs and showed the possibility of deconfinement driven by turbulence. The second configuration was rotating electric fields. Shunichiro discussed how the frequency of the electric field affects the phase transition and argued the possibility of a novel state, distinct from the vacuum, for infinitesimally small electric fields with finite frequency. Reported by Hidetoshi Taya

2021-08-13

Announcement

Agreement between RIKEN and Okinawa Institute of Science and Technology Graduate University on Cooperative Graduate School

RIKEN and the Okinawa Institute of Science and Technology Graduate University (OIST) signed an agreement on August 1, 2021, for the purpose of promoting mutual research exchange and contributing to the promotion of science and technology. Under the cooperative graduate school system, RIKEN and OIST will deepen their collaboration in human resource development by accepting graduate students from OIST to provide research guidance and other services at RIKEN, and by having RIKEN researchers give lectures at OIST. The collaborative professors to be appointed for this system include Dr. Shigehiro Nagataki (Deputy Program Director, iTHEMS).

2021-08-10

Seminar Report

Information Theory SG Seminar by Prof. Masayuki Ohzeki on August 4, 2021

On August 4, Prof. Masayuki Ohzeki (Tohoku University/Tokyo Institute of Technology/Sigma-i Co., Ltd.) gave us a talk on the quantum annealing. In the first part, after a general introduction, he demonstrated how to use the D-Wave machine from our personal computers. It is remarkable that we can easily manipulate a number of quantum spins ourselves to solve an optimization problem. In the second part, he reviewed working principles for quantum annealing: he started from the original proposal in 1998 and explained more recent methods such as the reverse annealing. He also explained carefully the usefulness and the limits of the quantum annealing. After discussing the theoretical perspective and how the machine is implemented using the superconducting qubits, he presented the application of the quantum annealer to the real world. He showed his collaborations with many companies and how the quantum annealing can be used to solve real-life problems, such as the optimization of the evacuation routes or listing the hotel recommendation on the web. A lot of interactive discussions were made during and after the talk. We really thank Prof. Ohzeki for his great talk. Reported by Ryusuke Hamazaki

2021-08-06

Seminar Report

iTHEMS Biology Seminar by Dr. Ai Niitsu on August 5, 2021

In iTHEMS biology seminar on August 5th, Dr. Ai Niitsu (RIKEN Theoretical Molecular Science Lab.) gave a talk about the membrane peptide design and computational modeling. First, she mentioned the recent machine learning approach for the prediction of the protein structures. Then, she pointed out that the prediction of the membrane related structure and stoichiometry of protein complexes is still challenging. Next, she explained the computational design of the coiled-coil peptides in membrane. The amino acid sequence of the peptide is determined so that the interchain interaction is satisfied. As a result, she obtained some stable transmembrane assemblies of the peptide. Along with the modelling of the peptide assemblies and their conductance estimate, she experimentally measured the conductance of the peptide channel in membrane by imposing various voltages. The high voltage induces the multi-conductance state, which differs from the low voltage case where a stable single channel was observed. Based on further computational modelling and experiments, that multi-conductance state was suggested to come from the change in the peptide structures and stoichiometry of a single pore. Her computational method and experimental results attract the audience interests and induce various discussions. Thank you very much for great talk, Ai! Reported by Hiroshi Yokota

2021-08-05

Paper of the Week

Week 2, August 2021

Title: LMC N132D: A mature supernova remnant with a power-law gamma-ray spectrum extending beyond 8 TeV Author: H. E. S. S. Collaboration arXiv: http://arxiv.org/abs/2108.02015v1 Title: Relativistic spin hydrodynamics with torsion and linear response theory for spin relaxation Author: Masaru Hongo, Xu-Guang Huang, Matthias Kaminski, Mikhail Stephanov, Ho-Ung Yee arXiv: http://arxiv.org/abs/2107.14231v1 Title: Convergence of a finite difference scheme for the Kuramoto--Sivashinsky equation defined on an expanding circle Author: Shunsuke Kobayashi, Shigetoshi Yazaki arXiv: http://arxiv.org/abs/2108.00593v1 Title: Locally equivalent quasifree states and index theory Author: Chris Bourne arXiv: http://arxiv.org/abs/2108.01230v1 Title: Toward ab initio determination of charge symmetry breaking strength of Skyrme functionals Author: Tomoya Naito, Gianluca Colò, Haozhao Liang, Xavier Roca-Maza, Hiroyuki Sagawa arXiv: http://arxiv.org/abs/2107.14436v1

2021-08-05

Person of the Week

Self-introduction: Congcong Le

My name is Congcong Le from China, and I join iTHEMS on August 1st 2021 as a Postdoctoral Researcher. After graduation, I came to the Institute of Physics, Chinese Academy of Sciences to study theoretical physics, and obtained my PhD in July 2017. My research focuses on the theoretical study in condensed matter systems, including unconventional superconductivity, strongly correlated system, and novel topological system (topological insulators, Dirac semimetal, Weyl semimetal), and I start to be interested in twisted bilayers and topological phases in the non-Hermitian systems. I have enjoyed using mathematics to explore condensed matter physics and working with theorists and experimenters. In my spare time, I like Chinese chess, badminton, table tennis and climbing.

2021-08-02

Seminar Report

Information Theory SG Seminar by Dr. Qibin Zhao on July 28, 2021

In the Information Theory SG seminar on July 28th, Dr. Qibin Zhao gave us an exciting talk about the basics and applications of tensor networks (TNs) in machine learning. His talk was divided into three parts, (i) tensor methods for data representation, (ii) TNs in deep learning modeling, and (iii) frontiers and future trends. In the first part, he started with a graphical introduction of tensors and dimension reduction methods. He then presented the important question of how the imperfect data represented by tensors can be completed using the low-rank approximation, and introduced several possible approaches with impressive examples. Here he explained the TNs and decomposition methods in detail using diagrammatic notations, which can concisely express the tensor operations such as the contraction. In the second part, he talked about the useful application of TNs to model compression in machine learning. He illustrated the ways to represent the neural network model by tensors and to learn the weights through the contraction. Interestingly, the density matrix renormalization group (DMRG), which was originally proposed in the quantum physics field, may be used as a learning algorithm. In the last part, he showed an overview of recent topics on TNs and machine learning such as TNs for probabilistic modeling and supervised learning with projected entangled pair states (PEPS). Intriguingly, the topological structure of TNs can be optimized for a given image, and the learned topology significantly depends on the input data and is more complex than conventional simple structures such as lines, trees, or cycles. The clearly structured talk took us from the basics to the cutting-edge subjects, and there were many questions and discussions during the talk. We are deeply grateful to Dr. Qibin Zhao for his excellent talk on the fast-growing interdisciplinary field. Reported by Kyosuke Adachi

2021-07-30

Seminar Report

iTHEMS Biology Seminar by Prof. Mayumi Seto on July 29, 2021

On July 29th, Mayumi Seto (Nara Women's University) gave a talk on the application of thermodynamics to microbial modeling. She first introduced some important concepts of adenosine tri-phosphate (ATP), its synthesis in biology, and chmotrophic interactions between microorganisms. She then moved on to mathematical models explicitly incorporating energy flows in the microbial interactions. She finally gave implications from her work for future and ongoing studies, and after the talk we casually discussed her exciting projects. For me, she was the person whom I met on the very first visitation at Kyushu University in 2009 when I was, as an undergrad student at another university, yet unsure to start my Ph.D. at Kyushu University or not, and I'm sure her kind and encouraging guidance was one of the decisive factors for me being here as a researcher. Thanks again for the fantastic talk, Mayumi! Reported by Ryosuke Iritani

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