179 news in 2021
On Feb. 22, our iTHEMS colleague, Gordon Baym, gave an online talk from Urbana-Champaign on the detection of the primordial neutrinos created in the early Universe. We are in the sea of those neutrinos at the present day with the neutrino density of about 56/cc for each neutrino species. Although neutrinos (anti-neutrinos) are left-handed (right-handed) in early Universe, both cosmic and galactic magnetic fields as well as the gravitational inhomogeneities can flip their spins with respect to the momentum, so that the helicities (spin projection along the direction of the momentum) of the relic neutrinos could be a new probe of cosmic gravitational and magnetic fields. More that 60 participants attended this interesting seminar and there were lively discussions during and after the talk.
On 18th February, we invited Junichiro Iwasawa from the University of Tokyo, who gave a talk about the unique study to identify the evolutionary constraints of drug-resistance in Escherichia coli using automated high-throughput laboratory experiments. He first talked about the background of drug resistance evolution and about the well-known / novel resistance-conferring genes for E. coli that were elucidated from their data. He then moved on to the details of the data analyses and explained the combined method of random forest regression and principal component analysis on the multi-omics data. We enjoyed a long discussion on every single detail of the impressive work. We especially thank him for accepting our invitation despite the tight schedule with his dissertation. Thank you again for the great talk! -Ryosuke Iritani
In iTHEMS biology seminar on Feb. 25th, Dr. Hiroshi Yokota (iTHEMS) talked about the mechanism of the non-linear response of DNA under stretching force. In the introduction part, he mentioned the experimental technique using the magnetic tweezer to measure the extension of DNA under stretching force, and he also showed the experimental results of the non-linear response of DNA. He then explained the strategy to clarify the origin of non-linearity by applying mathematical modeling and statistical physics. Introducing the worm-like chain model, he transformed the Hamiltonian in an elegant way and analytically obtained the formula of the extension, which explains the experimental data. His description of the model was very clear, and there were many questions and discussions. We are thankful to Hiroshi for the intriguing talk. Kyosuke Adachi
The paper "Indication of a Pulsar Wind Nebula in the hard X-ray emission from SN 1987A" by Dr. Shigehiro Nagataki (Deputy Program Director, iTHEMS), Dr. Masaomi Ono (Research Scientist, iTHEMS) and Mr. Akira Dohi (Junior Research Associate, iTHEMS) was published in the NASA and INAF press releases on February 23, 2021 (SN1987A's 34th birthday!). The following is a message from Dr. Nagataki; "We detected high-energy X-rays by NuSTAR, which are likely to come from activities of pulsar wind nebula of SN1987A (it has been a big mystery why the neutron star in SN1987A has not been detected for 34 years since Prof. Koshiba et al. detected neutrinos at the birth of proto-neutron star in SN198A). Our paper will be published by Astrophysical Journal Letters this week."
On 17th February, we had Ryusuke Hamazaki (from RIKEN Hakubi and iTHEMS) talking about the recent studies on the large deviation principle in our journal club of the Information Theory Study Group. He started off by demonstrating Bernoulli's process and how to compute the large deviations, and then defined the Level 2.5 large deviations in Markovian jump process, thereby providing the derivation of a recently proposed inequality (the thermodynamic uncertainty relation). Finally, he explained possible extensions to quantum systems. The talk received numerous questions in every single part, specifically from those interested in the derivation and application of the Level 2.5 large deviation. Thanks, Ryusuke, for the great and inspiring talk! Ryosuke Iritani (iTHEMS)
The precise understanding of the local DM density, as well as its velocity distribution, is critical for dark matter (DM) search, especially for direct detection experiments. We need information about the global structure such as the position and rotation velocity of the Solar system when evaluating these quantities. Astrometry, which is a technique to measure the time dependence of the position of stars, powerfully probes the 3D gravitational structure of our Galaxy. There are two types of astrometric observations: the first one is based on optical (and infrared) photometry. The parallax is obtained by comparing two snapshots of the sky between two epochs. The Gaia mission is the representative for this kind of observation. Gaia reveals the structure of our Galaxy up to ~5kpc from the Sun. The mission is planned to continue the observation to extend our reach to ~10kpc, meaning that it should cover the Galactic Center in the near future. The second one is the VLBI observation. VLBI is an abbreviation of the very-long baseline interferometry. The spatial resolution of milli-arcsecond is achieved with VLBI techniques. However, the sensitivity is limited and long-lasting observations are required in general. In this sense, VLBI and optical photometry are complemental. One important discovery for DM search from VLBI astrometry is reported in this seminar. The VLBI observation of the Galactic disk region reveals the position of the Sun is closer to the Galactic Center compared to the conventional values used for a long time, and the rotation velocity is higher. This means that our Galaxy is heavier, i.e. contains much DM, and the relative velocity between DM particle and us is different, compared with the previous estimates. Also, the disk region does not reach the equilibrium yet. These facts should change the picture of our Galactic DM structure. New facilities for astrometric observations are now being planned and constructed. There are diverse possibilities for the synergy between DM search. The astrometry should give important indications such as the merger history of DM halo, dynamical interaction between the Milky Way and its satellite galaxies, the global structure of the Milky Way, and far more. We should stay tuned!
On February 16, the iTHEMS-phys seminar entitled "Quantum mechanical description of energy dissipation and application to heavy-ion fusion reactions" given by Mr. Masaaki Tokieda (Tohoku U.) was held. He introduced his work during graduate school, that is, considering dissipation and fluctuation to the quantum mechanics to unify the description of above the Coulomb barrier and sub-barrier reactions. He also applied the method to heavy-ion fusion reactions. The seminar was held via the Zoom online conference systems. More than 20 people, including outside from iTHEMS, attended the seminar. The discussion was quite lively, and it was continued for long, even after the seminar.
In iTHEMS biology seminar on February 12, Keitaro Kume (Univ. of Tsukuba) gave us a talk about applying machine learning to the analysis of non-model organisms that are difficult to experiment with. First, Dr Kume introduced us about the brief mitochondrial evolution and several eukaryotes possessed not typical mitochondria as like Mitochondrion related organelle (MRO) which is highly degraded mitochondria. Next, he described the detection of mitochondrial localization signals and their applications, explaining that it is difficult to detect localization signals in mitochondria of non-model organisms, especially MROs. Finally, He obtained a large amount of data on MRO-localized proteins in non-model organisms, and through machine learning using the data as training data, he created a detector that can detect MRO-localized signals in such non-model organisms. He presented a good example of the connection between biological evolutionary research and machine learning, which led to a lively discussion at the seminar. Thank you very much, Kei!
Title: Quiescent luminosities of accreting neutron stars with different equation of states Author: Helei Liu, Akira Dohi, Masa-aki Hashimoto, Yasuhide Matsuo, Guo-Liang Lü, Tsuneo Noda arXiv: http://arxiv.org/abs/2102.04012v1 Title: An adjunction inequality for the Bauer Furuta type invariants, with applications to sliceness and 4-manifold topology Author: Nobuo Iida, Anubhav Mukherjee, Masaki Taniguchi arXiv: http://arxiv.org/abs/2102.02076v1
A research collaboration of Dr. Fumito Mori (Assistant Professor, Education and Research Center for Mathematical and Data Science/Faculty of Design, Kyushu University) and Dr. Takashi Okada (Senior Research Scientist, RIKEN iTHEMS) has developed a new theory for "Diagrammatic expansion of information flows in stochastic Boolean networks".
A five-year project titled "Material Evolution in the Universe — Nuclei, Atoms, Molecules, and Beyond" is underway at RIKEN starting in 2019. The project is led by the Dr. Sakai at Star and Planet Formation Laboratory, the Dr. Tamagawa at High Energy Astrophysics Laboratory, and the Dr. Nagataki at Astrophysical Big Bang Laboratory, and brings together researchers from inside and outside RIKEN. The goal is to realize a new type of space research that integrates physics and chemistry, and to understand the evolution of matter from nuclei to atoms to molecules.
On February 4, the iTHEMS-phys seminar entitled "Quantum kinetic theory for chiral and spin transport in relativistic heavy ion collisions and core-collapse supernovae" given by Dr. Di-Lun Yang (Keio U.) was held. He has been working for the quantum kinetic theory. In his seminar, first, he introduced the general background of the quantum transport of the massless fermions and its anomaly. Then, he showed its application to the relativistic heavy-ion collisions and core-collapse supernovae. The seminar was held via the Zoom online conference systems. More than 20 people, including outside from iTHEMS, attended the seminar. The discussion was quite lively, and it was continued for long, even after the seminar.
In iTHEMS Biology Seminar on Feb. 4th, Yoshifumi Asakura (Kyoto University) talked about modeling of the mechano-chemical dynamics of an epithelial sheet. He first reviewed experimental observation of the epithelial sheet dynamics with ERK signals and simple theoretical modeling of the mechano-chemical dynamics. He then presented the main questions, stressing the importance of two-dimensionality and parameter heterogeneity in tissue dynamics. In the method part, he introduced the hierarchical modeling which connects the particle-based and continuum models with the cell tracking data. He showed that the models can reproduce the essential features of the tissue dynamics with ERK signals, and moreover, can be used for the quantitative prediction of the velocity field of cells. His presentation contained many beautiful movies of the epithelial sheet dynamics and model simulations. We are thankful to him for the nice talk! Kyosuke Adachi
Title: Twisted crystallograpic T-duality via the Baum--Connes isomorphism Author: Kiyonori Gomi, Yosuke Kubota, Guo Chuan Thiang arXiv: http://arxiv.org/abs/2102.00393v1 Title: Most charming dibaryon near unitarity Author: Yan Lyu, Hui Tong, Takuya Sugiura, Sinya Aoki, Takumi Doi, Tetsuo Hatsuda, Jie Meng, Takaya Miyamoto arXiv: http://arxiv.org/abs/2102.00181v1 Title: Time to revisit the endpoint dilution assay and to replace TCID50 and PFU as measures of a virus sample's infection concentration Author: Daniel Cresta, Donald C. Warren, Christian Quirouette, Amanda P. Smith, Lindey C. Lane, Amber M. Smith, Catherine A. A. Beauchemin arXiv: http://arxiv.org/abs/2101.11526v1
A research collaboration of Prof. Makoto Mizuno (the Faculty of Commerce, Meiji University), Prof. Hideaki Aoyama (Senior Visiting Scientist, RIKEN iTHEMS) and others has developed a new econophysics method applicable to analyze marketing data.
My name is Björn Ahlgren. I joined iTHEMS as a visiting scientist in February 2021 as part of my current postdok, and I'm otherwise based at KTH in Stockholm, Sweden. My field of research is astrophysics, where I work mainly on gamma-ray bursts (GRBs), which are some of the most violent explosions in the Universe. These phenomena are caused by the collapse of particularly massive stars, and by compact object binary mergers, and they can serve both as laboratories for physics under extreme conditions, as well as probes of the early Universe. In my research I focus on the intersection between theory and observations, where I try to develop and reconcile theoretical models for the emission mechanisms of GRBs with the best available observations, using statistical methods. My specialisation lying in applied statistics, I really enjoy interdisciplinary projects where I get to work with new ideas and new data. I'm excited to join iTHEMS and I hope I will get the opportunity to engage in new collaborations across different disciplines.
On January 28, the iTHEMS-phys seminar entitled "Many body problems from quarks to stellar evolutions" given by Prof. Nobutoshi Yasutake (Chiba Institute of Technology/JAEA) was held. He has been working for the stelar evolutions as gravitational many-body problems and the hadronic matter as quantum many-body problems based on the Lagrangian schemes. Recently, he discussed hadronic matters properties using the color molecular dynamics. The seminar was held via the Zoom online conference systems. Around 20 people, including outside from iTHEMS, attended the seminar. The discussion was quite lively, and it was continued more than one hour even after the seminar.
Title: Drifting Dirac monopole in Berry's phase Author: Kazuo Fujikawa, Koichiro Umetsu arXiv: http://arxiv.org/abs/2101.10541v1 Title: Deconfining Phase Boundary of Rapidly Rotating Hot and Dense Matter and Analysis of Moment of Inertia Author: Yuki Fujimoto, Kenji Fukushima, Yoshimasa Hidaka arXiv: http://arxiv.org/abs/2101.09173v1
Today's journal club of the Information Theory Study Group had Hiroshi Yokota (iTHEMS) talk about the replica-permutation method to obtain stable structures. He started off the talk with some introduction of proteins' stable structures. To avoid reaching nonglobally optimal structures, the replica-exchange method used to be applied; however, this method may be computationally expensive and less efficient in some circumstances. Later work has proposed the replica-permutation method by which the candidates of the stable structures are permutated (shuffled) and relaxes the detailed balance condition. He drew an analogy with allocation problems of various volumed cups each filled with water. He finally talked about the application in a paper that examines amyloid 𝛽 oligomerization. The audience asked lots of questions about the algorithm per se, physical meaning, and even its potential applications. Thanks, Hiroshi, for the fantastic talk! I as well as arguably all the audience really enjoyed it! -Ryosuke Iritani (RIKEN iTHEMS)
On January 21st, Takashi Okada (RIKEN iTHEMS) gave a talk on Boolean networks at the iTHEMS Biology Seminar. He first introduced the basics of Boolean networks and their applications in Biology, and then talked about his recent work on information transfer in Boolean networks. Network is a theme that is common to almost all fields of Science and is relevant to most of us. Thus, his talk was very useful to get a basic idea of what Boolean network is and how it is applied. Not only the basic introduction, but also his recent work on information transfer was explained very clearly in simple terms, which made it possible for all of us to follow and enjoy. Thanks Takashi! - Jeffrey Fawcett
Title: Second and fourth moments of the charge density and neutron-skin thickness of atomic nuclei Author: Tomoya Naito, Gianluca Colò, Haozhao Liang, Xavier Roca-Maza arXiv: http://arxiv.org/abs/2101.07680v1 Title: Exploring effects of tensor force and its strength via neutron drops Author: Zhiheng Wang, Tomaya Naito, Haozhao Liang, Wen Hui Long arXiv: http://arxiv.org/abs/2101.04860v1
On January 7th, Dr. Koichiro Uriu gave a talk on one of the most important pattern formation in our body. Koichiro was an active member of iTHES, and is currently an assistant professor at Kanazawa Univ. Rhythmic (ON and OFF) and also spatial gene activity pattern, termed the segmentation clock underlies our body axis segmentation (“Taisetsu" in Japanese). Thus, robust gene activity oscillation propagates from the backward to the forward domain by which the segment is formed sequentially. In the seminar, Koichiro discussed the recovery processes of the segment formation after the removal of the drug which blocks oscillator coupling in a fish, called zebrafish. Curiously, experiments show that intermingled segments can occur in the body of the fish especially when the drug is removed at early stage. To understand the pattern recovery, he developed a physical model incorporating mechanics and genetic oscillations. During and after the talk, there were numerous questions from the audience because his talk was very interesting and also very clear. Thank you and see you, Koichiro! - Gen Kurosawa
On January 20th, Dr. Ryosuke Iritani gave us a talk about his motivation to work with information theory. He first formulated the dynamics of species-site data in ecology as a Markov model. By reducing the model to a simpler one in an elegant way, he analytically obtained the evolution of the proportion of species. In addition, he discussed certain entropies that characterize the diversity of species and showed us the unique dynamics of the entropy in his model. His talk was clear as he explained mathematical concepts by using simple examples and illustrations, and there were questions and comments from several viewpoints. We are thankful to Ryosuke for the exciting talk! Kyosuke Adachi (BDR/iTHEMS)
We are happy to invite Dr. Xueda Wen from Harvard University to give a talk on January 18th. This talk is the first seminar of the quantum matter study group. The topic is time-dependent driven quantum critical systems in (1+1) dimensions, which connects condensed matter physics and high energy physics. Dr. Wen started with two different free-fermion lattice Hamiltonians. The system is driven periodically and alternatively with these two Hamiltonians. Interestingly, this driven system leads to two distinct two phases. This straightforward introduction smoothly brought us to the study of time-dependent driven conformal field theories. The driven CFTs show that the periodical driving systems can possess heating and non-heating phases, and the phase transition boundary separates these two phases. Dr. Wen further talked about the generalization of driving CFTs and several unsolved problems. This talk is informative as well as interactive. Drs. Tada, Hongo, and Takasan asked several key questions, and Dr. Wen answered those questions clearly and informatively. We thank Dr. Wen for the great talk. --Ching-Kai Chiu
The Israeli popular magazine “Epoch” has featured Dr. Tomoki Ozawa, AIMR Junior Principal Investigator, in its December 2020 issue. The feature article describes his research on synthetic dimensions. Although we live in a three-dimensional space, scientists can now “artificially” create and study the equivalent of dimensions, which is different from ordinary ones. Dr. Ozawa uses “spin” of an atom as an example of a synthetic dimension. By using spin degrees of freedom as an additional dimension, it is possible to study higher dimensional physical phenomena, such as the four-dimensional quantum Hall effect. The article was published for the general public focusing on cutting-edge research on higher dimensions, also discussing their relations to science-fiction like parallel universe. The article contains an easy-to-follow description of the new idea of synthetic dimensions, which is accessible to general readers. We expect that the studies on synthetic dimensions to have impacts in a variety of fields, ranging from condensed matter physics to high-energy physics.
Title: A note on exotic families of 4-manifolds Author: Tsuyoshi Kato, Hokuto Konno, Nobuhiro Nakamura arXiv: http://arxiv.org/abs/2101.00367v1 Title: Local Operator Entanglement in Spin Chains Author: Eric Mascot, Masahiro Nozaki, Masaki Tezuka arXiv: http://arxiv.org/abs/2012.14609v1 Title: Chiral separation effect catalyzed by heavy impurities Author: Daiki Suenaga, Yasufumi Araki, Kei Suzuki, Shigehiro Yasui arXiv: http://arxiv.org/abs/2012.15173v1 Title: Tensor-force effects on shell-structure evolution in N = 82 isotones and Z = 50 isotopes in the relativistic Hartree-Fock theory Author: Zhiheng Wang, Tomoya Naito, Haozhao Liang arXiv: http://arxiv.org/abs/2012.13143v1 Title: Second order chiral kinetic theory under gravity and antiparallel charge-energy flow Author: Tomoya Hayata, Yoshimasa Hidaka, Kazuya Mameda arXiv: http://arxiv.org/abs/2012.12494v1 Title: Exceptional Dynamical Phase Transitions in Periodically Driven Quantum Systems Author: Ryusuke Hamazaki arXiv: http://arxiv.org/abs/2012.11822v1 Title: Fermion doubling theorems in 2D non-Hermitian systems for Fermi points and exceptional points Author: Zhesen Yang, A. P. Schnyder, Jiangping Hu, Ching-Kai Chiu arXiv: http://arxiv.org/abs/1912.02788v3
On January 13, Dr. Kyosuke Adachi gave a talk entitled “Accelerated equilibration in classical stochastic systems” at the journal club of information theory study group. First, he reviewed the concept of shortcuts to adiabaticity (STA) and discussed a two-level system as a concrete example. Then it was explained that STA are fast routes to the final states in quantum systems. Second, he introduced the engineered swift equilibration (ESE) in classical stochastic systems, which is a classical counterpart of STA. Indeed, he explained that the Fokker-Plank equation has a similar structure to the Schroedinger equation, and the fast routes from the initial equilibrium state to the final equilibrium state are ESE. As examples of ESE, compression of Brownian particles, and evolutionary systems were given. Finally, he mentioned some interesting questions. The talk had many stimulating discussions. We are grateful to Adachi-san for his excellent talk!
In iTHEMS biology seminar on January 14, Jeffery Fawcett (RIKEN iTHEMS) gave us a talk on what genes are and how we can identify them. He started from the basics such as chromosomes, genes, and how proteins are produced from them. He then explained difficulties in defining a gene. This sounds very interesting because most of us (at least, I) naively think that we know what a gene is, even without knowing a precise definition of it. He also explained how we can predict the location of genes on the chromosomes. Jeff nicely presented keys ideas for non-experts, and all of us enjoyed his talk. I am also working on evolutionary biology, but I have never thought seriously about how genes are identified, and his talk became a nice introduction to this fascinating topic. Thank you very much, Jeff! - Takashi Okada
It has been a long time since guerrilla rains have become a social problem, threatening our daily lives with localized and sudden fierce rains that cause flooding and power outages. However, current weather forecasting technology is unable to predict the occurrence of guerrilla rainstorms. Team leader Tatemasa Miyoshi (TL) of the Data Assimilation Research Team at the RIKEN Center for Computational Science (R-CCS) has developed an innovative weather forecasting method that takes in and updates observation data every 30 seconds, and is trying to realize guerrilla rainfall forecasting.
179 news in 2021