News
175 news in 2022

20220628
Research NewsRIKEN Research: Worming out of the blackhole information paradox
RIKEN physicist and two colleagues have found that a wormhole—a theoretical bridge connecting distant regions of the Universe—may help to shed light on the mystery of what happens to information about matter consumed by black holes. Einstein’s theory of general relativity predicts that nothing that falls into a black hole can escape its clutches. But in the 1970s, Stephen Hawking calculated that black holes should emit radiation when quantum mechanics, the theory governing the microscopic realm, is considered. “This is called black hole evaporation because the black hole shrinks, just like an evaporating water droplet,” explains Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences. To read more, please see related links.

20220627
Seminar ReportiTHEMS Math Seminar by Dr. Shou Yoshikawa on June 10, 2022
On June 10, Shou Yoshikawa gave an introductory talk on his research field. He started his talk by explaining what is an algebraic geometry in mixed characteristic. He then explained some recent results on this subject. Reported by Keita Mikami

20220623
Seminar ReportQuantum Matter Seminar by Dr. Nobuyuki Okuma on June 21, 2022
Quantum Matter Study Group invited Prof. Nobuyuki Okuma to give an online seminar about nonHermitian topological phases. The seminar started with a succinct introduction to nonHermitian matrices. Different from Hermitian systems, the energy spectra now become complex numbers, the bra and ket states become inequivalent, and the Hamiltonians are not always diagonalizable, leading to the emergence of exceptional points. Taking the HatanoNelson model as an example, the speaker studied the 1D chain with the imaginary gauge transformation and showed that the spectra strongly depend on the boundary conditions (being periodic or open). Furthermore, distinct from end modes in Hermitian topological insulators, skin effect arises in nonHermitian systems, with skin modes accumulating in one end of the chain. He further showed that this skin effect also exhibits topological nature and can be generalized to either higherdimensional systems or to other nonHermitian systems with Z2 topological invariants. Reported by ChenHsuan Hsu (YITP) and ChingKai Chiu

20220621
Seminar ReportiTHEMS Biology Seminar by Dr. Mitsusuke Tarama on June 16, 2022
On June 16th, Dr. Tarama gave us an interesting talk about the physical modeling of selforganization in the chick embryo. He first introduced several beautiful patterns in biology such as stripes of pigment cells of Zebrafish. He then explained a recent observation of the dynamical meshwork structure of chick mesodermal cells, which is the direct motivation of his theoretical work. He showed how the intercellular interactions and shape deformation of cells can produce the dynamical meshwork structure, by physical modeling and application of the persistent homology as a useful tool. We are really grateful to Dr. Tarama for his comprehensive talk from both experimental and theoretical sides. Reported by Kyosuke Adachi

20220620
Seminar ReportMathPhys Seminar by Dr. Daisuke Yoshida on June 16, 2022
Dr. Daisuke Yoshida first motivated the expectation that the true quantum gravity, whatever its form turns out to be, should be free from singularities in the universe. The "singularity theorem" by Penrose states that a spacetime singularity arises under a set of certain assumptions. Flipping the argument around, if one admits that singularities are absent in our universe, at least one of the assumptions in the theorem needs to be abandoned. Dr. Yoshida discussed general properties that a nonsingular universe must satisfy in order to avoid the singularity theorem. In particular, he found and explained that the universe must be, in some sense, smaller than the corresponding closed de Sitter spacetime. His talk stimulated the audience, and they continued discussions for long after his seminar. Reported by Ryo Namba

20220616
Paper of the WeekWeek 3, June 2022
Title: Reflected Entropy in Boundary/Interface Conformal Field Theory Author: Yuya Kusuki arXiv: http://arxiv.org/abs/2206.04630v1

20220609
Seminar ReportiTHEMS Biology Seminar by Dr. José Said GutiérrezOrtega on June 2, 2022
In this talk, I mentioned how both geographic isolation and natural selection may influence the way how species can be originated. I made emphasis in a general pattern that suggests that tropical species are more likely than highlatitude species to evolve while retaining the niche of their ancestors; a process called “niche conservatism”. To demonstrate this pattern, I showed the recent results of my own empirical research on the cycad genus Ceratozamia from Mexico: species at lower latitudes evolved niches less differentiated than expected from a Brownian Motion model (an evidence of niche conservatism), and highlatitude species evolved niches more differentiated than expected (an evidence of niche divergence). I hypothesize that both “niche conservatism” and “niche divergence” are not opposed processes as usually thought in ecology, but are part of a same general process. The implementation of models to predict how phylogenetic and ecological factors interplay in the formation of species along the latitudinal gradient may explain the pattern at the global level. The discussion on this topic allowed identifying that the latitudeassociated variation of biodiversity richness seems to be analogous to thermodynamic models: a higher energy availability in the tropics will make biological groups to evolve different ways (species) to exploit that energy. Reported by José Said GutiérrezOrtega

20220609
Paper of the WeekWeek 2, June 2022
Title: Ordered and tunable Majoranazeromode lattice in naturally strained LiFeAs Author: Meng Li, Geng Li, Lu Cao, Xingtai Zhou, Xiancheng Wang, Changqing Jin, ChingKai Chiu, Stephen J. Pennycook, Ziqiang Wang, HongJun Gao Journal Reference: Nature (2022) doi: https://doi.org/10.1038/s41586022047448 Title: Observing Supernova Neutrino Light Curves with SuperKamiokande. III. Extraction of Mass and Radius of Neutron Stars from Synthetic Data Author: Yudai Suwa, Akira Harada, Masayuki Harada, Yusuke Koshio, Masamitsu Mori, Fumi Nakanishi, Ken'ichiro Nakazato, Kohsuke Sumiyoshi, Roger A. Wendell arXiv: http://arxiv.org/abs/2204.08363v1 Title: Lindbladian ManyBody Localization Author: Ryusuke Hamazaki, Masaya Nakagawa, Taiki Haga, Masahito Ueda arXiv: http://arxiv.org/abs/2206.02984v1 Title: Semiclassical Gravity from Averaged Boundaries in twodimensional BCFTs Author: Yuya Kusuki arXiv: http://arxiv.org/abs/2206.03035v1 Title: Evaluations of uncertainties in simulations of propagation of ultrahighenergy cosmicray nuclei derived from microscopic nuclear models Author: E. Kido, T. Inakura, M. Kimura, N. Kobayashi, S. Nagataki, N. Shimizu, A. Tamii, Y. Utsuno arXiv: http://arxiv.org/abs/2206.03447v1 Title: Protoneutron Star Convection Simulated with a New General Relativistic Boltzmann Neutrino RadiationHydrodynamics Code Author: Ryuichiro Akaho, Akira Harada, Hiroki Nagakura, Wakana Iwakami, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, Kohsuke Sumiyoshi, Shoichi Yamada arXiv: http://arxiv.org/abs/2206.01673v1 Title: Semianalytical frameworks for subhalos from the smallest to the largest scale Author: Nagisa Hiroshima, Shin'ichiro Ando, Tomoaki Ishiyama arXiv: http://arxiv.org/abs/2206.01358v1 Title: Ring isomorphisms of type II$_\infty$ locally measurable operator algebras Author: Michiya Mori arXiv: http://arxiv.org/abs/2206.00875v1 Title: Universal van der Waals force between heavy polarons in superfluids Author: Keisuke Fujii, Masaru Hongo, Tilman Enss arXiv: http://arxiv.org/abs/2206.01048v1

20220609
Hot TopicRIKENBerkeley Center was opened
RIKEN iTHEMS and N3AS Physics Frontier Center have started a joint research center, RIKENBerkeley Center (RBC), physically located on the 3rd floor of the physics building in Univ. California, Berkeley. This new Center aims to enhance the collaboration on nuclear astrophysics and quantum information science between the two institutions. On May 2729, 2022, the first annual meeting of N3AS was held in Berkeley together with their international partners, RIKEN iTHEMS and CNRS Centre Pierre Binetruy. iTHEMS members are encouraged to use RBC as a base to interact with researchers in physics, mathematics, biology and related fields at Berkeley.

20220609
Person of the WeekSelfintroduction: Akira Matsumoto
I am Akira Matsumoto. I was in KEK until March 2022 as a student of SOKENDAI and got my Ph.D. there. Then I came to RIKEN and joined iTHEMS as a postdoctoral researcher in May 2022. I am interested in nonperturbative nature of gauge theories such as quantum chromodynamics (QCD), which describes the dynamics of quarks and gluons. Since these elementary particles are building blocks of matter, QCD is the important key to understanding history of our universe. The most powerful method of studying QCD is the Monte Carlo simulation based on the lattice gauge theory. So, we can simulate the dynamics of QCD on a supercomputer. However, in some cases, the Monte Carlo method is not applicable due to the socalled sign problem. For example, QCD with the chemical potential or with the topological theta term suffer from this problem. Since they are related to the structure of neutron star and the strong CP problem, the sign problem is a major obstacle to understanding such phenomena. I am studying and developing methods to avoid this problem. There are some conventional approaches such as the complex Langevin method and the tensor renormalization group. I am also trying to apply recently developing quantum computation to the simulation of gauge theories. I expect we can overcome the sign problem by using these methods in near future.

20220608
Seminar ReportDMWG Seminar by Dr. Shintaro Eijima on June 6, 2022
Dark matter (DM) is one important ingredient of our Universe of which existence indicates the theory beyond the Standard Model. It is not the unique motivation to extend the Standard Model describing the visible world. For example, we need to explain the origin of the tiny neutrino mass and the matterantimatter asymmetry. The introduction of sterile neutrinos could solve these problems simultaneously. Sterile neutrinos are new species of neutrinos which communicate with the Standard Model neutrino (active neutrinos) through mixing. Unfortunately, the possibility of explaining the whole of DM with the sterile neutrinos is already excluded from observations of Xray emission, neutrino beam experiments, and cosmological requirements. However, it is still a viable candidate when we consider the production mechanism carefully. Furthermore, some of such scenarios expect large lepton asymmetries resulting in the matterantimatter asymmetry. The sphaleron process takes an important role in such scenarios and it is related to the electroweak phase transition in the early Universe. The process of fixing the lepton asymmetry is interesting: sterile neutrinos first freezein, then freezeout, and decay. Quantitative prediction of such processes requires sophisticated calculations. Dr. Eijima has shown the latest results in this talk, with the comments that the bottleneck to proceed is the computational costs. The methodology is already welldeveloped. We will see indicative predictions in the near future! Neutrino physics will open new windows for our Universe! Reported by Nagisa Hiroshima

20220608
Seminar ReportABBLiTHEMS Joint Astro Seminar by Dr. Kanji Mori on June 3, 2022
Axionlike particles (ALPs) are a class of hypothetical bosons that feebly interact with ordinary matter. The hot plasma of stars and corecollapse supernovae is a possible laboratory to explore physics beyond the standard model, including ALPs. Once produced in a supernova, some of the ALPs can be absorbed by the supernova matter and affect energy transfer. The speaker recently consistently calculated the ALP emission in corecollapse supernovae and the backreaction on supernova dynamics. It is found that the stalled bounce shock can be revived if the coupling between ALPs and photons is as high as $g_{a\gamma}\sim 10^{9}$ GeV$^{1}$ and the ALP mass is 40400 MeV. Reported by Shigehiro Nagataki

20220608
AwardDr. Yuki Yokokura received The 13th RIKEN Research Incentive Award (Ohbu Award)
Yuki Yokokura (Senior Research Scientist, iTHEMS) received "The 13th RIKEN Research Incentive Award (Ohbu Award)" on March 23, 2022 for his outstanding achievement in the "Study of Quantum Black Holes". Congratulations!

20220606
Hot TopicRyosuke Iritani was interviewed by The Big Issue of Japan
Ryosuke Iritani (Research Scientist, iTHEMS) is interviewed by The Big Issue Japan, and the latest volume (vol 432) is just published on 1st June. The Big Issue is a magazine dedicated to supporting people in difficult circumstances and helping them achieve selfreliance. Each issue costs 450 yen, out of which 230 yen is the direct income of the street sales staff. The content is about mathematical biology and is accessible for anyone. We hope as many people as possible take it a read and support the people!

20220606
Press ReleaseCommon Laws of Evolution and Ecological Dynamics
The research team of Kyosuke Adachi (Special Postdoctoral Researcher, iTHEMS / Special Postdoctoral Researcher, Nonequilibrium Physics of Living Matter RIKEN Hakubi Research Team, RIKEN Center for Biosystems Dynamics Research (BDR)), Ryosuke Iritani (Research Scientist, iTHEMS) and Ryusuke Hamazaki (Senior Research Scientist, iTHEMS / RIKEN Hakubi Team Leader, Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team, RIKEN Cluster for Pioneering Research (CPR)) have proposed a broadly valid formula for theoretical models of evolutionary and ecological population dynamics using methods from information theory and statistical physics. The results of this research are expected to lead to a unified framework for understanding complex population dynamics in evolutionary and ecological systems over time. For more information, please see the related link.

20220602
Paper of the WeekWeek 1, June 2022
Title: Evaporation of Echoing Black Holes Author: Naritaka Oshita, Hayato Motohashi, Sousuke Noda arXiv: http://arxiv.org/abs/2205.15342v1 Title: Viscosity suppresses rprocess viable outflows in global models of collapsar disks Author: Oliver Just, Miguel A. Aloy, Martin Obergaulinger, Shigehiro Nagataki arXiv: http://arxiv.org/abs/2205.14158v1 Title: On a singular limit of the KobayashiWarrenCarter energy Author: Yoshikazu Giga, Jun Okamoto, Koya Sakakibara, Masaaki Uesaka arXiv: http://arxiv.org/abs/2205.14314v1 Title: Complementarity and causal propagation of decoherence by measurement in relativistic quantum field theories Author: Yoshimasa Hidaka, Satoshi Iso, Kengo Shimada arXiv: http://arxiv.org/abs/2205.08403v2 Title: Angular Momentum Inheritance from the Schwinger Effect in (Chromo)electromagnetic Fields Author: Patrick Copinger, Yoshimasa Hidaka arXiv: http://arxiv.org/abs/2203.10917v1

20220530
Seminar ReportMathPhys Seminar by Dr. Toshifumi Noumi on May 19, 2022
Dr. Toshifumi Noumi (Kobe University) gave a pedagogical seminar on the socalled swampland program in particle physics. The program aims to clarify nontrivial consistency conditions on symmetries in quantum gravity that leave implications for particle physics and cosmology. Dr. Noumi started out with the basic philosophy of the study and expanded the details using the arguments of symmetries, blackholes, holography etc., keeping accessibility for broad audience. Reported by Ryo Namba

20220530
Seminar ReportiTHEMS Math Seminar by Dr. Yuto Moriwaki on May 23, 2022
On May 23, there was a math seminar by Yuto Moriwaki. He gave an introductory talk on the mathematical formulation of CFT. Reported by Keita Mikami

20220530
Seminar ReportiTHEMS Biology Seminar by Dr. Dan Warren on May 19, 2022
In the Biology Seminar on May 19th, 2022, we had the great opportunity to have Dr. Dan Warren (Okinawa Institute of Science and Technology, Japan) as an invited speaker. In his talk, Dr. Warren explained why the evaluation of species distribution models (SDMs) has become a useful method to understand and predict the geographic distribution of species. In particular, they provide vital information to take measurements in the conservation of biodiversity. To construct SDMs, researchers in this field have taken advantage of publicity available geographic and environmental big data. Usually, those kind of data were not produced with the intention to use it in ecology, but ecologists have developed many methods to use the big data to answer questions in ecology and evolutionary biology. However, despite that several of those methods have become standard in ecology, Dr. Warren warns us that all commonly used methods have serious biases, and such biases might be related to how much we unquestionably rely that big data. To explain his point, he showed the results of one paper that he and his colleagues recently published. In that paper, the authors used occurrence data of a fictional animal: the Pokémon Kangaskhan (name in English) or ガルーラ (in Japanese), and followed the usual methods to construct SDMs in order to predict the Pokémon distribution in the Australian territory. They found that the distribution of the fictional animal has strong biases, and that same patterns of biases are also present in many other reallife species. Dr. Warren concluded that there is a big open field to improve methods to construct SDMs. The incorporation of prior information in the construction of SDMs, and the application of Markov chain Monte Carlo methods to account for the uncertainty of results might be effective solutions to solve the problems that persist in this research field. Reported by José Said GutiérrezOrtega

20220530
Seminar ReportSeminar by Dr. Teppei Kitahara on May 20, 2022
Dr. Teppei Kitahara from Nagoya University gave a comprehensive review of anomalies from the Standard Model in particle physics. Continuous development of experiments in recent years has revealed a large number of experimental anomalies which the Standard Model cannot explain. It is statistically obvious that as the number of experiments increases, one encounters a new anomaly due to the statistical fluctuation. But interestingly, some of the anomalies have been crosschecked by different experiments. These would be hints for physics beyond the Standard model. In his seminar, he focused on the flavor anomalies (also known as lepton flavor universality violation), the muon g2 anomaly, and recently measured the W boson mass anomaly. He also discussed these implications for the new physics and introduced several of his works. Reported by Etsuko Itou

20220526
Paper of the WeekWeek 5, May 2022
Title: Reheating after relaxation of large cosmological constant Author: Paul Martens, Shinji Mukohyama, Ryo Namba arXiv: http://arxiv.org/abs/2205.11754v1 Title: Accuracy of onedimensional approximation in neutron star quasinormal modes Author: Hajime Sotani arXiv: http://arxiv.org/abs/2205.10523v1 Title: Attractive $N$$φ$ Interaction and TwoPion Tail from Lattice QCD near Physical Point Author: Yan Lyu, Takumi Doi, Tetsuo Hatsuda, Yoichi Ikeda, Jie Meng, Kenji Sasaki, Takuya Sugiura arXiv: http://arxiv.org/abs/2205.10544v1

20220523
Seminar ReportABBLiTHEMS Joint Astro Seminar by Dr. Yannis Liodakis on May 20, 2022
The origin of highenergy neutrinos is fundamental to our understanding of the Universe. Apart from the technical challenges of operating detectors deep below ice, oceans, and lakes, the phenomenological challenges are even greater. The sources are unknown, unpredictable, and we lack clear signatures. Neutrino astronomy therefore represents the greatest challenge faced by the astronomy and physics communities thus far. The possible neutrino sources range from accretion disks and tidal disruption events, through relativistic jets to galaxy clusters with blazar TXS 0506+056 the most compelling association thus far. Since then, immense effort has been put into associating AGNjets with highenergy neutrinos, but to no avail. The speaker discussed his current efforts in understanding the multimessenger processes in the Universe, and once and for all proving or disproving if AGNjets are neutrino emitters. Reported by Shigehiro Nagataki

20220519
Paper of the WeekWeek 4, May 2022
Title: Gyrohydrodynamics: Relativistic spinful fluid with strong vorticity Author: Zheng Cao, Koichi Hattori, Masaru Hongo, XuGuang Huang, Hidetoshi Taya arXiv: http://arxiv.org/abs/2205.08051v1 Title: Event reconstruction of Compton telescopes using a multitask neural network Author: Satoshi Takashima, Hirokazu Odaka, Hiroki Yoneda, Yuto Ichinohe, Aya Bamba, Tsuguo Aramaki, Yoshiyuki Inoue arXiv: http://arxiv.org/abs/2205.08082v1 Title: Running Hubble constant from the SNe Ia Pantheon sample? Author: Tiziano Schiavone, Giovanni Montani, Maria Giovanna Dainotti, Biagio De Simone, Enrico Rinaldi, Gaetano Lambiase arXiv: http://arxiv.org/abs/2205.07033v1 Title: The Prime Number Theorem and Pair Correlation of Zeros of the Riemann ZetaFunction Author: D. A. Goldston, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2205.06503v1

20220518
Seminar ReportiTHEMS Math Seminar by Dr. Taketo Sano on May 13, 2022
In May 13, there was a math seminar by Taketo Sano. He gave an introductory talk on category theory. Reported by Keita Mikami

20220509
Press ReleaseDiscovering Speed Limits for Macroscopic Transitions  A Unified Approach Based on the Equation of Continuity
Ryusuke Hamazaki (RIKEN Hakubi Team Leader, Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team / Senior Research Scientist, iTHEMS) has discovered a new inequality for the “speed limit," or transition rate, which is useful for physical processes that involve "macroscopic transitions". The research results are expected to have implications for nonequilibrium statistical mechanics, including the time scale of thermalization of quantum manybody systems. They are also expected to contribute to the fundamental understanding of quantum technology, e.g., the control of macroscopic quantum systems, which has become important in recent years. Please see related link for more details.

20220509
Press ReleaseClear Visualization of Lamb Waves from Tonga's Undersea Volcano Eruption The Full Picture of the Waves Captured by the Himawari8
Takemasa Miyoshi (Deputy Program Director, iTHEMS / Team Leader, Data Assimilation Research Team, RIKEN Center for Computational Science (RCCS)) and Shigenori Otsuka (Research Scientist, iTHEMS / Research Scientist, Data Assimilation Research Team, RIKEN Center for Computational Science (RCCS)) have developed an original method to clearly visualize "Lamb waves," a type of sound wave associated with Tonga's undersea volcanic eruption in January 2022, using images from the Himawari 8 meteorological satellite. Furthermore, we developed a method to automatically extract the Lamb waves from this image and clarified the relationship between the distribution of arrival times and ground pressure observations. The results of this research are expected to contribute to the scientific understanding and monitoring of atmospheric waves and associated tidal fluctuations caused by volcanic eruptions, and to the development of advanced simulations and future forecasting methods by integrating observation data with largescale atmospheric and oceanographic calculations. Please see related links for more details.

20220505
Paper of the WeekWeek 2, May 2022
Title: High energy emission component, population, and contribution to the extragalactic gammaray background of gammaray emitting radio galaxies Author: Yasushi Fukazawa, Hiroto Matake, Taishu Kayanoki, Yoshiyuki Inoue, Justin Finke arXiv: http://arxiv.org/abs/2204.14019v1 Title: The $a$points of the Riemann zetafunction and the functional equation Author: Athanasios Sourmelidis, Jörn Steuding, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2204.13887v1 Title: Speed Limits for Macroscopic Transitions Author: Ryusuke Hamazaki Journal Reference: PRX Quantum 3, 020319 (2022) doi: https://doi.org/10.1103/PRXQuantum.3.020319 arXiv: http://arxiv.org/abs/2110.09716v3

20220430
Seminar ReportiTHEMS Biology Seminar by Mr. Daiki Kumakura on April 28, 2022
On April 28th, I talked about the Asgard archaea and the theory of intracellular symbiosis and discussed the mathematical modeling of the symbiosis hypothesis. First, I gave a brief of the classification of the organism as a fivekingdom system and threedomain system. Next, I talked about Asgard archaea, a group of archaea that has received much attention recently. Finally, I discussed the culture of Asgard archaea and the new theory of intracellular symbiosis that has developed as a result. In my presentation, I prepared the idea of mathematical modeling for the new theory. Audience members gave a variety of opinions on this model. In particular, I discussed points where the evolutionary model should be added, whether deterministic or stochastic dominance contributed, and why symbiosis was possible only in two specific species although a variety of symbiotic relationships were possible. I had a meaningful time exchanging opinions and having discussions with various researchers. Thank you so much. Reported by Daiki Kumakura

20220428
AwardTakemasa Miyoshi and Yuji Sugita received 2022 MEXT Commendation for Science and Technology
Takemasa Miyoshi (RCCS Team Leader/ iTHEMS Deputy Director) received "2022 MEXT Commendation for Science and Technology" for "Study on Big Data Assimilation to Innovate Numerical Weather Forecasting". Congratulations! Yuji Sugita (CPR Chief Scientist/ iTHEMS Senior Research Scientist) received "2022 MEXT Commendation for Science and Technology" for "Theoretical Study on Dynamic Structure of Biomolecules in the Intracellular Environment". Congratulations!

20220428
Seminar ReportiTHEMS Colloquium by Dr. HongYan Shih on April 22, 2022
On April 22 (Fri), we had the first iTHEMS colloquium of FY2022 by inviting HongYan Shih from Academia Sinica, Taiwan. After reviewing the turbulent phenomena in various area of science, she discussed how the turbulence occurs by increasing the flow velocity and how one can develop an effective theory to describe the critical region of laminarturbulent transition. Then she discussed a remarkable mathematical relation between the effective theory with the predatorprey dynamics in ecology and showed a characteristic super exponential scaling law. The topic was an ideal subject for the interdisciplinary talk, and there were many questions from the researchers with different scientific backgrounds.

20220428
Paper of the WeekWeek 5, April 2022
Title: Visualizing Lamb Waves From a Volcanic Eruption Using Meteorological Satellite Himawari8 Author: Shigenori Otsuka Journal Reference: Geophysical Research Letters, 49, e2022GL098324 (2022) doi: https://doi.org/10.1029/2022GL098324

20220428
Seminar ReportIntroduction to Topological Insulators by Dr. Tomoki Ozawa on April, 2022
In this lecture series, Professor Ozawa gave an introduction to topological insulators which are materials whose wavefunctions show nontrivial topological structures in momentum space. In the first two lectures, he introduced the socalled SuSchriefferHeeger model and the bulkedge correspondence which links edge states with winding number of certain operator in the Hamitonian. Such correspondence has its origin in mathematics called Toeplitz Index theorem which is a special case of AtiyahSinger index theorem. In the last two lectures, Chern insulators and quantum metrics are introduced. Eigenvectors of the Hamiltonian define a map from the momentum space (typically a torus) to a complex projective space. The pullback FubiniStudy metric (and standard Kahler form) defines the socalled quantum metric (and Berry curvature) on the momentum space. Using ChernWeil theory, Chern classes/characters are then defined. Chern classes which are originally notions from differential geometry/topology play an important role in topological insulators. A necessary and sufficient condition is also given when the above mentioned map is an immersion and realises momentum space as a Kahler submanifold of the projective space. Reported by Yalong Cao

20220425
Seminar ReportiTHEMS Math Seminar by Dr. Cédric Ho Thanh on April 22, 2022
On April 22, there was a math seminar by Dr. Cédric Ho Thanh. In the first half, he explained the recurrence theorems for the topological Markov chain. In the second half, he explained the sketch of the proof. Reported by Keita Mikami

20220425
Research NewsRIKEN Research: Quantum computing and deep learning could help solve the mysteries of quantum gravity
RIKEN physicists have put quantum computing and deep learning through their paces and found that they are powerful tools for gleaning insights into new theories of quantum gravity [1]. They could thus help solve one of the most formidable challenges in modern physics—developing a theory of gravity that jives with quantum physics. When Einstein nutted out his theory of general relativity in 1915, his only tools were pen and paper. The same was true of the pioneers of quantum theory. But the next major breakthrough in theoretical physics could be made with help from emerging technologies such as quantum computers and machine learning, Enrico Rinaldi of RIKEN Theoretical Quantum Physics Laboratory thinks. “I believe these technologies are poised to transform the way we do theoretical physics,” he says. To read more, please visit the related link.

20220425
Hot TopiciTHEMS x academist online event was held on April 24, 2022
As the alternative for the lectures at RIKEN’s annual open house, iTHEMS held another online lecture event for the general public with the help of Academist Inc., on April 24th, 2022. This year, the lectures were Masaki Taniguchi, Hidetoshi Taya, Akira Harada, Yingying and Euki Yazaki, who all gave splendid public lectures accessible even to juniorhigh school students. Each lecturer also served as a commentator to another lecture, asking questions on behalf of the audience. During the lunch break, Program Director Hatsuda showed the offices of iTHEMS and around. The event was moderated by Ms. Michibayashi from Academist; Her facilitation with a wit kept the event lively. At one time during the event, more than two hundred audiences participated.

20220425
Seminar ReportABBLiTHEMS Joint Astro Seminar by Dr. Masanori Iwamoto on April 22, 2022
Dr. Masahiro Iwamoto gave a presentation on his recent threedimensional (3D) particleincell (PIC) simulation of relativistic shocks and application of the results of the 3DPIC simulations to astrophysical phenomena. For example, the origin of fast radio bursts (FRBs; Lorimer et al. 2007) is one of the unsolved problems in astrophysics. Many observations of FRBs indicate that FRBs must be coherent emission in the sense that coherently moving electrons radiate electromagnetic waves. In relativistic shocks, it is well known that coherent electromagnetic waves are excited by synchrotron maser instability (SMI) in the shock transition (Hoshino & Arons 1991). The SMI is also known as the emission mechanism of coherent radio sources such as auroral kilometric radiation at Earth and Jovian decametric radiation. Recently, some models of fast radio burst based on the coherent emission from relativistic shock via the SMI have been proposed (e.g., Lyubarsky 2014; Beloborodov 2017; Plotnikov & Sironi 2019; Metzger et al. 2019) and the SMI in the context of relativistic shocks attracts more attention from astrophysics. In this seminar, by performing the world’s first 3DPIC simulation of relativistic shocks, he demonstrated that largeamplitude electromagnetic waves are indeed excited by the SMI even in 3D and that the wave amplitude is significantly amplified and comparable to that in pair plasmas due to a positive feedback process associated with ionelectron coupling. Based on the simulation results, he discussed the applicability of the SMI for FRBs. Reported by Shigehiro Nagataki

20220422
Paper of the WeekWeek 4, April 2022
Title: GRB Prompt Emission: Observed Correlations and Their Interpretations Author: Tyler Parsotan, Hirotaka Ito arXiv: http://arxiv.org/abs/2204.09729v1 Title: Fedder type criteria for quasi$F$splitting Author: Tatsuro Kawakami, Teppei Takamatsu, Shou Yoshikawa arXiv: http://arxiv.org/abs/2204.10076v1

20220420
Person of the WeekSelfintroduction: José Said GutiérrezOrtega
¡Hola! This is José (ホセ). I am a Mexican biologist in search of knowledge and interactions with scientists in all disciplines. I obtained my bachelor's degree in Mexico and completed my graduate studies in Japan: two countries where I grew up as a researcher, and where I also had great experiences working in science education. I joined iTHEMS as a SPDR in April 2022, and this transition represented an extraordinary chance for me to expand my research lines and interests. My scientific background is in evolutionary biology and ecology. Therefore, the main questions that motivate my studies are “how is the origin of the species?”, “why are species the way they are?”, “why do species change over time?”, “how do species interact with the environment and other species?”. To answer that kind of questions, I have gained abilities in phylogenetics, phylogeography, population genetics, plant systematics, botany, taxonomy, and population ecology. If these prior skills are useful for your research, or if you want to start something completely new, I am always available to work together with you. よろしくおねがいします！

20220418
AnnouncementInvitation from "Science": "What is Mass? The Fundamental Nature of Matter in the Universe and Its Origin" will be broadcast on Sunday, April 24, on the Open University of Japan (BS 231ch)!
A fourpart series focusing on the fundamental physics concept of "mass" and the historical evolution of its understanding will be broadcast on Sunday, April 24, on the Open University of Japan (BS 231ch). Tetsuo Hatsuda (Program Director, iTHEMS), Koichi Yazaki (Research Consultant, iTHEMS), and Gordon Baym (Senior Visiting Scientist, iTHEMS) will appear in "Part 4: Do we now know the origin of mass of matter?." The broadcast will air on Sunday, May 15 at 20:15 and Sunday, June 26 at 8:15 (rebroadcast). For more information, please see the related links.

20220418
Person of the WeekSelfintroduction: Yuto Moriwaki
Quantum field theory is a physical theory that describes a wide range of phenomena from the subatomic world to the cosmic scale, and can be regarded as a fruit of human wisdom. However, quantum field theory has not yet been mathematically formulated. This problem perhaps asks us, "How do we formulate space?" According to the philosophy of algebraic geometry, "space and algebra" are almost the same thing. Here, the algebra is a collection of functions (classical fields). So let us consider the algebra consisting of quantum fields. The "classical algebra" is associative, whereas the "quantum algebra" is nonassociative. What should be the corresponding space? I am currently studying this algebra of quantum fields in the case of twodimensional quantum field theory. In my previous research, I have worked mathematically on (1) a formulation of the algebra of twodimensional conformal field theory, (2) constructions of examples, and (3) a construction of nonperturbative deformations. More recently, I have returned to the question of "space" a bit, studying the axioms (consistency) of quantum field theory from a viewpoint of an operad structure of moduli spaces and higher categories. I was originally a pure mathematician studying representation theory. Crossing the field into physics has been fruitful for my life, although there is still a lot I don't understand. I am very happy to be here at iTHEMS and hope to have good interactions and coevolution with many researchers.

20220415
Person of the WeekSelfintroduction: Shou Yoshikawa
My name is Shou Yoshikawa. I joined RIKEN iTHEMS as an SPDR in April 2022. I am a mathematician studying algebraic geometry. I am interested in an analog of the existence of KählerEinstein metric to positive characteristic. Algebraic geometry in positive characteristic is a purely mathematical subject, however, the Einstein metric is deeply related to Physics. I hope that we find a new relation between mathematics and other sciences studying such analogies.

20220415
Person of the WeekSelfintroduction: Daiki Kumakura
My name is Daiki Kumakura. I joined iTHEMS as JRA (Junior Research Associate) in April 2022. My research fields are microbial evolutionary ecology and mathematical biology. Still undergraduate, I researched the metabolism of deep marine microbes with transcriptome analysis and comparative genome analysis. Because I am interested in the evolutionary process of microbes with the ecological interactions, I currently have researched the coevolution of microbes with theoretical analysis. Then, I do interdisciplinary research of fieldwork and theoretical simulation. The main field is a hot spring (Japanese is an onsen). I sample the sediments and water at each location and do bioinformatics. In the theoretical analysis, I construct mathematical modeling and simulation. I have the unique experience of discussing with theoretical researchers in various fields at iTHEMS. Through this interdisciplinary research and discussion, I hope to make my doctoral course meaningful.

20220415
Person of the WeekSelfintroduction: Taketo Sano
My name is Taketo Sano. I joined iTHEMS as a special postdoctoral researcher in April 2022 after I got the Ph.D. in mathematical sciences from the University of Tokyo. My research area is in lowdimensional topology and knot theory. I am interested in the intersection of (or interaction between) topology and combinatorics. Spaces are inherently infinite and beyond direct computations, while their algebraic images (under some nice mappings) are usually more tractable, and in some cases algorithmically computable. When one finds nice properties in the algebraic level, it is natural to expect that they are reflections of some hidden structures in the spacial level. My aim is to investigate the nature of the unseeable spaces through their algebraic images, by using theoretical tools (from algebraic topology, homotopy theory and category theory) together with computer powers.

20220414
Paper of the WeekWeek 3, April 2022
Title: The closest lineage of Archaeplastida is revealed by phylogenomics analyses that include Microheliella maris Author: Euki Yazaki, Akinori Yabuki, Ayaka Imaizumi, Keitaro Kume, Tetsuo Hashimoto, Yuji Inagaki Journal Reference: Open Biology 12: 210376 (2022) doi: https://doi.org/10.1098/rsob.210376 Title: Quantum Simulation for High Energy Physics Author: Christian W. Bauer. Zohreh Davoudi, A. Baha Balantekin, Tanmoy Bhattacharya, Marcela Carena, Wibe A. de Jong, Patrick Draper, Aida ElKhadra, Nate Gemelke, Masanori Hanada, Dmitri Kharzeev, Henry Lamm, YingYing Li, Junyu Liu, Mikhail Lukin, Yannick Meurice, Christopher Monroe, Benjamin Nachman, Guido Pagano, John Preskill, Enrico Rinaldi, Alessandro Roggero, David I. Santiago, Martin J. Savage, Irfan Siddiqi, George Siopsis, David Van Zanten, Nathan Wiebe, Yukari Yamauchi, Kübra YeterAydeniz, Silvia Zorzetti arXiv: http://arxiv.org/abs/2204.03381v1 Title: GoussarovPolyakViro Conjecture for degree three case Author: Noboru Ito, Yuka Kotorii, Masashi Takamura arXiv: http://arxiv.org/abs/1905.01418v3

20220414
Seminar ReportiTHEMS Biology Seminar by Dr. Hiroshi Yokota on April 14, 2022
In iTHEMS biology seminar on April 14th, I introductory talked about the coarsegrained molecular dynamics simulation by using Langevin equation which is the equation of motion including the interaction, the friction and the random force. First, I mentioned the chromosome formation dynamics as an example of the application range of the simulation. Next, I explained the Langevin equation and its intuitive picture. Then, I showed the discretized Langevin equation which keeps the stochastic properties of the random force term. Finally, I showed some examples of Langevin simulation. Many questions and discussions arose from the audience. Thank you very much!

20220411
Hot TopiciTHEMS Starter Meeting for FY2022 on April 8, 2022
The iTHEMS Starter Meeting for FY 2021 was held over Zoom as past two years’ meeting to kick off its activity for FY 2022. Over seventy iTHEMS members, frequent visitors and colleagues from other institute got together and introduced each other.

20220408
Research NewsRIKEN Research: Ringing black holes could put general relativity to the test
Typical overtone chords in the gravitational waves produced when black holes collide could be used to test general relativity, a mathematical analysis by a RIKEN physicist has shown [1]. When black holes merge, they generate gravitational waves, which ripple outward like sound waves from a ringing bell. In theory, these gravitational waves can be broken down into tones and overtones—like in music—based on their different frequencies and the rate at which they dampen and die out. But in practice, gravitationalwave detectors are not yet sensitive enough to definitively pick up the overtones. However, cosmologists are keen to measure the precise oscillation pattern because it can tell them more about a black hole’s properties. In particular, the mass of the black hole and the rate at which it is spinning can be calculated from the damping rate and frequency. “It’s like when you hear an instrument, you can understand if it is a guitar or a piano,” says Naritaka Oshita of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS). To read more, please visit the related link.

20220407
Person of the WeekSelfintroduction: Makiko Nio
She has been involved in precision calculations of Quantum Electrodynamic(QED), such as energy spectra of simple hydrogenlike atoms and the anomalous magnetic moments of the electron and the muon. The results of the calculations are used to determine the value of the finestructure constant that governs any electromagnetic phenomena. The QED results are also essential to test the Standard Model(SM) of elementary particles and to find something new beyond the SM by comparing theoretical predictions to measurements.

20220407
Paper of the WeekWeek 2, April 2022
Title: Ribbon YetterDrinfeld modules and tangle invariants Author: Kazuo Habiro, Yuka Kotorii arXiv: http://arxiv.org/abs/2204.02551v1 Title: Dominant Andreev Reflection through Nonlinear RadioFrequency Transport Author: Tingyu Zhang, Hiroyuki Tajima, Yuta Sekino, Shun Uchino, Haozhao Liang arXiv: http://arxiv.org/abs/2204.01356v2

20220406
Research NewsThe Horse: Breeding Mares Early in Life Might Lead to Early Fertility Decline
Jeffrey Fawcett (Senior Research Scientist, iTHEMS) and his research was featured in an article in The Horse. If you want to breed an older mare, you might consider how old she was when she was first bred. According to a new study in Japanese racehorses, broodmare fertility appears to decrease slowly over the years, on a downhill slope that follows her number of breeding years—and not just her age. “Our results suggest that the fertility of a mare is the highest at (her) first year breeding and gradually declines every year,” said Jeffrey Fawcett, PhD, a biologist and senior research scientist at RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS), in Saitama, Japan. To read more, please visit the related link.
175 news in 2022