# News

179 news in 2021

2021-05-11

Press Release

## Mystery of Wasps That Produce Few Males Solved

A collaborative research group, including Dr. Ryosuke Iritani (Research Scientist, iTHEMS), has solved the mystery of wasps that produce only a few percent of males. See related link for details.

2021-05-10

Person of the Week

## Self-introduction: Hidetoshi Taya

My name is Hidetoshi Taya. After finishing my Ph. D in The University of Tokyo in 2017, I had several postdoctoral positions at iTHEMS RIKEN (2017-18), Fudan University (2018-20), and Keio University (2020-21) and then come back to iTHEMS, RIKEN from April, 2021 as a special postdoctoral researcher. I am a theoretical physicist working on (but not limited to) particle and nuclear physics. In particular, I am interested in non-perturbative and non-equilibrium phenomena driven by strong fields, and studying their application to, for example, heavy-ion collisions, intense lasers, and condensed-matter systems. I am also interested in application of mathematical methods such as the resurgence theory and the exact WKB method. I look forward to interacting with iTHEMS members and to enjoying something new/interesting together.

2021-05-10

Person of the Week

## Self-introduction: Yuya Kusuki

I am Yuya Kusuki. I joined iTHEMS in April 2021. I am studying the theoretical particle physics. My particular interest is conformal field theory in the context of the AdS/CFT. For example, I would like to understand “Which spectrum and which coupling constants are required to reproduce the semiclassical gravity?”, “Whether or not does a pure gravity on AdS exist?”, “What is the precise definition of the quantum chaos in AdS/CFT?” and so on. For this purpose, I mainly utilize (i) some information tools, developed in the interface between quantum gravity and quantum information, and (ii) conformal bootstrap equation. I am looking forward to collaborating with researchers in various fields at iTHEMS. Since my research is based on gravity, conformal field theory, information theory, condensed matter, that is, many topics, I believe such a cross-disciplinary collaboration provides wonderful results.

2021-05-06

Seminar Report

## iTHEMS Biology Seminar by Dr. Yukinori Nishigami on April 22, 2021

In iTHEMS biology seminar on April 22, Dr. Yukinori Nishigami (Hokkaido Univ.) gave us a talk about his research results, such as modeling the swimming behavior of unicellular organisms in their environment. First, Dr. Nishigami introduced us to the diversity of unicellular eukaryotes and the fact that they have their own specific movements. Many of the participants were amazed at how a small, single-celled organism can move in complex ways using flagella and other mechanisms, and how the cells themselves can move in complex ways. Next, he talked about the main topic: modeling the phenomenon of ciliate accumulation in a stable environment. Through careful observation and simulation, he modeled the movement and found that the movement of ciliates in such an environment is due to the simple principle of cell shape and mechanosensitivity of cilia. He presented a good example of modeling the behavior of unicellular organisms, which led to a lively discussion at the seminar. Thank you very much, Nishigami-san! Reported by Euki Yazaki

2021-05-06

Event Schedule

## Events for the 3rd week of May 2021

Wednesday, May 12, 10:00- DMWG Seminar Wednesday, May 12, 17:00- Quantum Matter Seminar Friday, May 14, 10:00- iTHEMS Biology Seminar Friday, May 14, 12:30- Coffee Meeting Friday, May 14, 16:00- Math Seminar

2021-05-06

Paper of the Week

## Week 2 of May, 2021

Title: Asymptotic behavior of fronts and pulses of the bidomain model Author: Hiroshi Matano, Yoichiro Mori, Mitsunori Nara, Koya Sakakibara arXiv: http://arxiv.org/abs/2105.00169v1 Title: Na+/Ca2+ exchanger mediates cold Ca2+ signaling conserved for temperature-compensated circadian rhythms Author: Naohiro Kon, Hsin-tzu Wang, Yoshiaki S. Kato, Kyouhei Uemoto, Naohiro Kawamoto, Koji Kawasaki, Ryosuke Enoki, Gen Kurosawa, Tatsuto Nakane, Yasunori Sugiyama, Hideaki Tagashira, Motomu Endo, Hideo Iwasaki, Takahiro Iwamoto, Kazuhiko Kume, Yoshitaka Fukada Journal Reference: Science Advances, Vol. 7, no. 18, eabe8132 doi: https://dx.doi.org/10.1126/sciadv.abe8132

2021-04-29

Paper of the Week

## Week 5 of April, 2021

Title: Hydrodynamic Attractor in a Hubble Expansion Author: Zhiwei Du, Xu-Guang Huang, Hidetoshi Taya arXiv: http://arxiv.org/abs/2104.12534v1 Title: Deep Learning of the Eddington Tensor in the Core-collapse Supernova Simulation Author: Akira Harada, Shota Nishikawa, Shoichi Yamada arXiv: http://arxiv.org/abs/2104.13039v1 Title: Positive scalar curvature and homology cobordism invariants Author: Hokuto Konno, Masaki Taniguchi arXiv: http://arxiv.org/abs/2104.10860v1

2021-04-28

Seminar Report

## Information Theory SG Seminar by Prof. Yoshihiko Hasegawa on April 28, 2021

On April 28, Prof. Yoshihiko Hasegawa (Associate Professor, The University of Tokyo) gave us a talk on the thermodynamic uncertainty relation (TUR). In the first part of his talk, he started from a motivation to consider trade-off relations between energy and cost, showing biological examples. After reviewing general theory of stochastic thermodynamics and TUR for classical Markovian systems, he presented two recent works of him: one is to derive the TUR from information-theoretic method (i.e., the Cramer-Rao bound) and the second is to derive it from the fluctuation theorem. In the second part, he discussed quantum version of the TUR. After the review of quantum dynamics under measurement, he showed the quantum TUR for general open systems. He applied his theory to continuously measured systems and explained its physical meaning. There were a lot of interactive discussions during and after the talk. We really thank Prof. Hasegawa for his great talk. Reported by Ryusuke Hamazaki

2021-04-23

Seminar Report

## Quantum Matter Seminar by Dr. Se Kwon Kim on April 21, 2021

On April 21st, Dr. Se Kwon Kim from KAIST gave a talk about unconventional spin transport in quantum materials. First, he gave an overview of spintronic physics. The advancements in spintronic techniques can potentially lead to new applications, such as quantum information science. Then, he showed the realization of magnonic topological insulators, which are Chern insulators with spin current but without electron charge current. Furthermore, he predicted that spin transport induces vortex flow in superconductors. We thank Dr. Kim for giving a wonderful talk. Reported by Ching-Kai Chiu

2021-04-22

Event Schedule

## Events for the 5th week of April 2021

Wednesday, April 28, 13:30- Information Theory SG Seminar Thursday, April 29, Shōwa Day (National Holiday!) Friday, April 30, 12:30- Coffee Meeting

2021-04-22

Paper of the Week

## Week 4 of April 2021

Title: Born-Oppenheimer potential energy surfaces for Kohn-Sham models in the local density approximation Author: Yukimi Goto arXiv: http://arxiv.org/abs/2104.09057v1 Title: Note on the Goldbach Conjecture and Landau-Siegel Zeros Author: D. A. Goldston, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2104.09407v1

2021-04-22

Seminar Report

## Math-Phys Joint Seminar by Prof. Takuju Zen on April 13, 2021

On April 13, Dr. Takuju Zen from Kochi University of Technology gave a talk entitled “Self-adjoint extension in quantum mechanics and non-Rydberg spectra of one-dimensional hydrogen atom” at the iTHEMS Math-Phys joint seminar. In the first part, he briefly explained the necessity of self-adjointness of operators in quantum mechanics and gave some important examples of such operators. Besides, he mentioned that the self-adjointness of Laplacian is equivalent to flux conservation in one dimension. Finally, he introduced studies of quantum particles on graphs. In the second part, the speaker discussed one dimensional Coulomb problem. Mainly, he noted that a simple self-adjoint extension of such hamiltonian could not be used. Then he provided a concrete procedure to study the solutions of one dimensional Coulomb problem and explained his interesting results. Reported by Yukimi Goto

2021-04-21

Seminar Report

## iTHEMS Colloquium by Prof. Kenji Fukaya on April 16, 2021

On April 16, 2021, 13:30-15:00 (JST) 0:30-2:00(EDT), Professor Kenji Fukaya, Simons Center for Geometry and Physics, Stony Brook University, gave a colloquium talk by zoom. The title was "Mirror symmetry and KAM theory". His talk began at the origin of symplectic geometry, namely, the Hamiltonian dynamics. He reviewed completely integrable Hamiltonian systems, where the first integrals define foliation by half dimensional Lagrangian tori with linear flows. The KAM (Kolmogorov-Arnold-Moser) theory describes perturbation of this system and shows that almost all tori persist. Then Professor Fukaya explained the Lagrangian torus fibration found by Strominger-Yau-Zaslow, with the example of the complex projective space. For the complex projective n-space, the image of the moment map is an n-simplex and the regular fibers are Lagrangian n-tori. The inverse image of the boundary of the simplex corresponds to the singular fiber of the holomorphic fibration (the product of homogeneous coordinates) to a disk, By choosing a symplectic form, around the singular fiber of holomorphic fibration, there is defined the monodromy map by using the Hamiltonian flow of the Hamiltonian function that is the absolute value of the fibering. Professor Fukaya told that for this example in dim n = 2, the monodromy near the singular fiber exhibits the KAM theoretic behavior, but in dim n = 3, it is not the case with respect to the Fubini-Study symplectic form. However, he expects it can be the case with respect to the Calabi-Yau Kaehler form. This correspondence between symplectic manifolds (the torus fibration of the complex projective space) and complex manifolds (the holomorphic map to the disk) is an introductory example of the mirror symmetry. His talk might enter much deeper part related with homological mirror symmetry, but he stopped and concluded by saying that the KAM theory explains the transition from completely integrable systems to chaos and it should be possible to find alternative in mirror symmetry or field theory which will explain the transition from stable system to chaos. The talk of Professor Fukaya was really stimulating and his enthusiasm impressed the audience. Reported by Takashi Tsuboi

2021-04-19

Hot Topic

## The iTHEMS x academist online public event was held on April 18, 2021

Following last year’s precedent, iTHEMS held an online lecture event for the general public with the help of Academist Inc., on April 18th, 2021. The event was planned as an alternative for the lectures at RIKEN’s annual open house. The event was started by Kanato Goto with his talk on Blackhole and its information problem. His compelling narrative evoked a lot of questions from high school students; some of them were very sharp. Next, Jeffery Fawcett talked about genome science. Among other topics he studied, he also mentioned the mutation of COVID-19 virus. During the lunch break, Program Director Hatsuda talked with Mr. Shibato from Academist about related books, the exhibition of Black Hole Recorder at Miraikan, and the attempts with RIKEN SUURI. In the afternoon, Sugiura-san talked about the supercomputers and the analysis of subatomic physics, followed by Naomi Tsuji's talk on supernovae and their remnants. The talk included several polls from the audience. Keita Mikami concluded the event with his talk on Mathematics, in particular inequality and differential equations. All the talks were compered by Ms. Michibayashi from Academist; Her facilitation with a wit kept the talks accessible even to high school students. The event was viewed by as many as more than three hundred audiences at one time.

2021-04-16

Seminar Report

## Quantum Matter Seminar by Dr. Mario Flory on April 14, 2021

On April 14th, from Instituto de Física Teórica, Universidad Autonoma de Madrid and Consejo Superior de Investigaciones Científicas, in Spain, Dr. Mario Flory gave a seminar talk about the connection between the AdS/CFT correspondence and condensed matter physics. In the first half of the talk, he briefly reviewed the ideas of the correspondence and its history. The most important breakthrough is that Juan Maldacena first proposed the AdS/CFT in the late '90s. It is known that the entropy of the black hole is proportional to its area, so that this feature suggests a holographic principle. The AdS/CFT correspondence serves a better understanding of this principle by connecting strongly coupled CFTs to classical gravity. In the second half, Dr. Flory addresses the important application of the correspondence to condensed matter physics. Because of the AdS/CFT correspondence, the problems of the Kondo model in condensed matter physics can be tackled by solving gravity problems. He specifically discussed the entanglement problem through the correspondence in detail. We thank Dr. Flory for giving an excellent talk. Reported by Thore Posske and Ching-Kai Chiu

2021-04-15

Hot Topic

## iTHEMS Starter Meeting for FY 2021 on April 9, 2021

iTHEMS officially kicked off its activity for FY 2021 by the iTHEMS Starter Meeting for FY 2021, on April 9th 2021. The meeting was held over Zoom as last year's meeting. Over sixty iTHEMS members gathered together as well as several frequent visitors and colleagues from other institute, and introduced themselves to other members.

2021-04-15

Event Schedule

## Events for the 4th week of April 2021

The iTHEMS x academist online open to the public "Mathematical Science World" and the MACS Colloquium are scheduled for next week. Sunday, April 18, 10:00- iTHEMS x academist Online open to the public "Mathematical science world" Thursday, April 22, 10:00- iTHEMS Biology Seminar Friday, April 23, 12:30- Coffee Meeting Friday, April 23, 15:00- MACS Colloquium

2021-04-15

Paper of the Week

## Week 3 of April 2021

Title: Approximate Bayesian Computation of Bézier Simplices Author: Akinori Tanaka, Akiyoshi Sannai, Ken Kobayashi, Naoki Hamada arXiv: http://arxiv.org/abs/2104.04679v2 Title: Detailed analysis of excited state systematics in a lattice QCD calculation of $g_A$ Author: Jinchen He, David A. Brantley, Chia Cheng Chang, Ivan Chernyshev, Evan Berkowitz, Dean Howarth, Christopher Körber, Aaron S. Meyer, Henry Monge-Camacho, Enrico Rinaldi, Chris Bouchard, M. A. Clark, Arjun Singh Gambhir, Christopher J. Monahan, Amy Nicholson, Pavlos Vranas, André Walker-Loud arXiv: http://arxiv.org/abs/2104.05226v1

2021-04-15

Seminar Report

## iTHEMS Biology Seminar by Dr. Kyosuke Adachi on April 15, 2021

In iTHEMS Biology Seminar on April 15th, Kyosuke Adachi (BDR/iTHEMS) talked about the formation mechanism and the biological function of liquid condensates in eucaryotic cell. First, he explained the higher-order structure of the chromatin fiber. He focused on A compartment and B compartment, in which the high and low transcription activities are shown, respectively. Then, he talked about the biomolecular condensate which is the liquid droplet composed of proteins. He talked about the important interaction on the condensate creation and explained the theoretical model based on the mean field theory. Finally, he explained the role of the condensates on the transcription activity. The transcription occurs in the condensates of some proteins coexisting on the chromatin fiber. The audience enjoyed his attractive talk. Thank you very much for great talk, Kyosuke! Reported by Hiroshi Yokota

2021-04-15

Seminar Report

## iTHEMS Biology Seminar by Prof. Catherine Beauchemin on April 8, 2021

In iTHEMS Biology Seminar on April 8th, Catherine Beauchemin (Deputy Program Director of RIKEN iTHEMS and Professor of Ryerson University) gave us an introductory talk on Markov chain Monte Carlo (MCMC) method. Many of theoretical scientists often use mathematical models, but it is difficult to correctly estimate parameter values of the model from experimental data. In this seminar, Catherine taught us the MCMC method is a powerful tool for parameter estimation using her recent research on cancer as an example. First, she explained four simple models of cancer growth. Then, using these models, she explained the basic idea and the detail process of the MCMC method. Her talk was very clear. I think that the seminar became helpful for the many attendees because the method can be applied to various fields of science and engineering. Merci beaucoup, Catherine! Reported by Shingo Gibo

2021-04-15

Seminar Report

## Journal Club of Information Theory SG by Dr. Yukimi Goto on April 14, 2021

On 14th April, Dr. Yukimi Goto gave an introduction to trace inequalities and related topics in our journal club of the Information Theory Study Group. She started from a simple counter example of the triangle inequality for operators on Hilbert space, and introduced density matrices, von Neumann entropy and Wigner-Yanase skew information. Then, she explained the concept of jointly convex/concave functions and Wigner-Yanase-Dyson-Lieb theorem, and discussed the sub-additivity and strong sub-additivity of von Neumann entropy and its generalizations. Thank you, Goto-san, for interesting talk! Reported by Akinori Tanaka

2021-04-14

Book

## The Future of 'Useless' Research

Authors: Tetsuo Hatsuda, Yoshinori Ohsumi and Sayaka Oki Editor: Ryosuke Shibato Language: Japanese What is "useful"? What does it mean to "study"? Thinking about science, budget, and our future with researchers on the front lines!

2021-04-14

Book

## Deep Learning and Physics

Author: Akinori Tanaka, Akio Tomiya and Koji Hashimoto Language: English Is the first machine learning textbook written by physicists so that physicists and undergraduates can learn easily. Presents applications to physics problems written so that readers can soon imagine how machine learning is to be used. Offers the starting point for researchers in the rapidly growing field of physics and machine learning.

2021-04-12

Seminar Report

## Math Seminar by Dr. Kai Koike on April 7, 2021

On April 7, Dr. Kai Koike from Kyoto University gave a talk entitled “Long-time behavior of moving solids in a fluid and the kinetic theory of gases” at Math seminar. In the first part, he reviewed a moving boundary problem of gases. Then he introduced some interesting results in fluid dynamics and developments concerning his research. In the second part, the speaker explained his results about the long-time behavior of a point particle moving in a fluid. It is an explanation of related numerical results for a BGK model of the Boltzmann equation. Reported by Yukimi Goto

2021-04-09

Event Schedule

## Events for the 3rd week of April 2021

The iTHEMS Colloquium and three iTHEMS seminars are scheduled for next week (red). If you are interested, you can also attend the other seminars (blue). And don't forget about the iTHEMS Starter Meeting today! (April 9, 12:30-) Tuesday, April 13, 16:00- Math-Phys Joint Seminar Wednesday, April 14, 17:00- Quantum Matter Seminar Thursday, April 15, 10:00- iTHEMS Biology Seminar (TBD) Friday, April 16, 13:30- iTHEMS Colloquium

2021-04-08

Award

## Tomoki Ozawa and Hidetoshi Nishimori received the FY2021 MEXT Commendation for Science and Technology

The Ministry of Education, Culture, Sports, Science and Technology (MEXT) announced the recipients of the FY2021 Commendation for Science and Technology. Our colleague Tomoki Ozawa (Associate Prof. at AIMR in Tohoku Univ. and iTHEMS Visiting Scientist) received "Commendation for Science and Technology: the Young Scientists' Award" in recognition of his outstanding research achievements in the theoretical studies of topological physics in atomic and photonic systems. Our colleague Hidetoshi Nishimori (Specially Appointed Professor, Tokyo Institute of Technology, and iTHEMS senior visiting scientist) received "Commendation for Science and Technology: Prize for Science and Technology" in recognition of his outstanding research achievements in developing the fundamental theory of quantum annealing.

2021-04-05

Seminar Report

## Math Seminar by Dr. Wataru Kai on March 22, 2021

On March 22, the last iTHEMS Math seminar in FY 2020 was held. This time, we invited Wataru Kai from Tohoku University. The title of the talk was “The Green-Tao theorem for number fields”. The main topic of the talk was his recent joint work with his collaborators about the Green-Tao theorem and its generalization. In the first part, he explained the historical background and the technology behind the proof of the Green-Tao theorem, which asserts that there are arbitrarily long arithmetic progressions of prime numbers. In the second part, he introduced algebraic numbers and algebraic integers, which generalize rational numbers and integers, respectively, and he explained how we can generalize the Green-Tao theorem to this situation. For example, if we think of numbers of the form a+b\sqrt{5}, these are algebraic numbers. Plotting them on the ab-plane, each of the numbers corresponds to a lattice point. We can draw a “shape” by choosing finite number of those lattices. Then, the generalized Green-Tao theorem asserts that, by applying scaling and parallel translation, we can make all of the chosen lattice points correspond to prime elements simultaneously. Here, prime element is a generalization of prime number in the world of algebraic numbers. He also explained that at some point of the proof of the generalized Green-Tao theorem, a classical technique well-known to algebraic number theorists plays a fundamental role. Reported by Hiroyasu Miyazaki

2021-04-02

Seminar Report

## Biology Seminar by Dr. Yuji Hirono on April 1st, 2021

In iTHEMS biology seminar on April 1st, Yuji Hirono (Assistant Professor, Asia Pacific Center for Theoretical Physics, POSTECH, Korea) gave us a talk on chemical reaction networks. Hirono-san has been recently working on chemical reaction networks with Miyazaki-san, Hidaka-san, and me. In the seminar, he talked about a new method of studying chemical reaction networks from network topology. He first explained graph theoretical aspects of chemical reaction systems, and then explained how these tools can be used to characterize reaction systems. Then, he explained a method of simplifying/deforming chemical reaction systems without affecting steady-state properties. I am grateful to Hirono-san because I could improve my understanding of reaction systems through collaboration with him. Also, Hirono-san and I have been friends since we were undergraduates, and I am happy to work together. Thank you very much, Hirono-san! Reported by Takashi Okada

2021-04-02

Event Schedule

## Events for the 2nd week of April 2021

Do you know about the iTHEMS Event Calendar? If you've been getting a lot of seminar invitations in the mail and don't know what to do with them, please take a look at the iTHEMS Event Calendar. Just add it to your Google Calendar and new seminars will be added automatically. Adding to your Google Calendar is very easy. Just click on the "+Google Calendar" button at the bottom right of the calendar. Don't miss a seminar you want to attend! Check it out! Yeah!

2021-04-02

Research News

## RIKEN RESEARCH: Supernova simulations reveal how stellar explosions shape debris clouds

Astronomers are now in a better position to interpret observations of supernova remnants thanks to computer simulations of these cataclysmic events by RIKEN astrophysicists.

2021-04-02

Hot Topic

## New faces in April 2021

April is the season when we have new faces. Yesterday, 10 people have joined us. Welcome to iTHEMS and let's have fun in science together!

2021-04-01

Paper of the Week

## Week 1 of April 2021

Sorry for not being updated since February due to a system error. Title: Impacts of new small-scale N-body simulations on dark matter annihilations constrained from cosmological 21cm line observations Author: Nagisa Hiroshima, Kazunori Kohri, Toyokazu Sekiguchi, Ryuichi Takahashi arXiv: http://arxiv.org/abs/2103.14810v1 Title: Quantifying the relative contribution of free virus and cell-to-cell transmission routes to the propagation of hepatitis C virus infections in vitro using an agent-based model Author: Kenneth Blahut, Christian Quirouette, Jordan J. Feld, Shingo Iwami, Catherine A. A. Beauchemin arXiv: http://arxiv.org/abs/2102.05531v1 Title: Arithmetic and geometric deformations of $F$-pure and $F$-regular singularities Author: Kenta Sato, Shunsuke Takagi arXiv: http://arxiv.org/abs/2103.03721v2 Title: Codimension 2 transfer of higher index invariants Author: Yosuke Kubota arXiv: http://arxiv.org/abs/2103.04741v1 Title: Dynamic sampling bias and overdispersion induced by skewed offspring distributions Author: Takashi Okada, Oskar Hallatschek arXiv: http://arxiv.org/abs/2103.05852v2 Title: Dual Labor Market and the "Phillips Curve Puzzle" Author: Hideaki Aoyama, Corrado Di Guilmi, Yoshi Fujiwara, Hiroshi Yoshikawa arXiv: http://arxiv.org/abs/2103.06482v1 Title: Dirac Fermion Cloning, Moiré Flat Bands and Magic Lattice Constants in Epitaxial Monolayer Graphene Author: Qiangsheng Lu, Ching-Kai Chiu, Congcong Le, Jacob Cook, Xiaoqian Zhang, Xiaoqing He, Mohammad Zarenia, Mitchel Vaninger, Paul F. Miceli, Chang Liu, Tai-Chang Chiang, Giovanni Vignale, Guang Bian arXiv: http://arxiv.org/abs/2103.10401v1 Title: Functional-renormalization-group approach to classical liquids with short-range repulsion: a scheme without repulsive reference system Author: Takeru Yokota, Jun Haruyama, Osamu Sugino arXiv: http://arxiv.org/abs/2103.11375v1 Title: The bulk-dislocation correspondence for weak topological insulators on screw-dislocated lattices Author: Yosuke Kubota arXiv: http://arxiv.org/abs/2103.13277v1 Title: Structural reduction of chemical reaction networks based on topology Author: Yuji Hirono, Takashi Okada, Hiroyasu Miyazaki, Yoshimasa Hidaka arXiv: http://arxiv.org/abs/2102.07687v1 Title: Optical Spin Transport in Ultracold Quantum Gases Author: Yuta Sekino, Hiroyuki Tajima, Shun Uchino arXiv: http://arxiv.org/abs/2103.02418v2 Title: Improving Schrödinger Equation Implementations with Gray Code for Adiabatic Quantum Computers Author: Chia Cheng Chang, Kenneth S. McElvain, Ermal Rrapaj, Yantao Wu arXiv: http://arxiv.org/abs/2103.08056v1 Title: Diagnosis of information scrambling from Hamiltonian evolution under decoherence Author: Tomoya Hayata, Yoshimasa Hidaka, Yuta Kikuchi arXiv: http://arxiv.org/abs/2103.05179v1 Title: Nuclear energy density functionals from empirical ground-state densities Author: Giacomo Accorto, Tomoya Naito, Haozhao Liang, Tamara Niksic, Dario Vretenar arXiv: http://arxiv.org/abs/2103.10096v1

2021-03-26

Seminar Report

## Biology Seminar by Dr. José Gutiérrez on March 25, 2021

On March 25th, José Gutiérrez from Chiba University gave a talk at iTHEMS Biology Seminar about the evolution and diversification of cycads ("sotetsu" in Japanese) in Mexico. He explained how the different species and populations of cycads are distributed in different areas of Mexico, and showed how this can be explained by changes in the climate and the adaptation of each species to the different environment. He then discussed some general ideas of how speciation and diversification can occur. It was probably the first time for many iTHEMS members to hear about research in Ecology, and I think many of us learned something new. We were also able to have a nice and fruitful discussion after the talk. Reported by Jeffrey Fawcett

2021-03-26

Hot Topic

## Message from the Director at the end of FY2020

I would like to thank all the iTHEMS members and iTHEMS supporting staff for your great efforts to keep iTHEMS very active during FY2020 even under the Covid-19. Our iTHEMS mission is very simple. Good science under the environment of interdisciplinary interactions: "A+B --> A*, A+ B --> B*, A+B --> C" are all in line with this mission. We will have many newcomers joining iTHEMS from FY2021, and let us keep moving forward without boundaries. Now, I would like to congratulate the two iTHEMS students: Toshihiro Ota (student trainee from Osaka Univ.) and Keisuke Fujii (student trainee from Tokyo Institute of Technology) who successfully defended their Ph.D. and are going to graduate from their Universities and from iTHEMS. I hope you have enjoyed your stay in iTHEMS and let us keep in touch for further interactions. Last but not the least, I would like to thank our assistant Izumi Nagasawa who has made tremendous support for the web page, seminars, colloquiums etc and is leaving iTHEMS at the end of this March. Although we could not see her so frequently in person under Covid-19 situation, she has been really helping our activities from behind. We send her our heartfelt gratitude.

2021-03-25

Award

## Dr. Takumi Doi receives 12th annual RIKEN Research Incentive Award

Takumi Doi (Senior Research Scientist, iTHEMS) received "FY2020 Researcher Incentive Award" on March 17, 2021 for his recent paper; Possible lightest Ξ Hypernucleus with Modern ΞN Interactions, published in Phys. Rev. Lett. 124, 092501(1-5) (2020), and related works. Congratulations !

2021-03-25

Award

## Dr. Masaomi Ono receives 12th annual RIKEN Research Incentive Award

Masaomi Ono (Research Scientist, iTHEMS) received "FY2020 Researcher Incentive Award" on March 17, 2021 for his recent paper; Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single-Star and Binary Merger Progenitor Models for SN 1987A, published in The Astrophysical Journal, 888, 111 (2020), and related works. Congratulations !

2021-03-25

Hot Topic

## Exhibition of "Black Hole Recorder"

At the National Museum of Emerging Science and Innovation (Miraikan) located in Tokyo, iTHEMS exhibition of "Black Hole Recorder" was held last week (March 14-15, March 17-21). Details of this outreach activity (Black Hole Recorder) and the general concept behind (UselessPrototyping Studio) can be seen from the URLs below.

2021-03-25

Seminar Report

## Information Theory SG by Dr. Akinori Tanaka on March 24, 2021

On 24th March, Dr. Akinori Tanaka gave an introduction to the reinforcement learning (RL) in our journal club of the Information Theory Study Group. He started from simple examples of a maze and a chess game to introduce the fundamental variables (i.e., states, actions, and rewards) and their evolution as a Markov decision process.After explaining that the goal of the RL is to maximize the value function, he discussed policy improvement theorem with the application to the epsilon-greedy update. We thank Akinori for the great and clear talk!

2021-03-18

Seminar Report

## Quantum Matter Seminar by Prof. Takahiro Morimoto on March 16, 2021

On March 16th, Prof. Takahiro Morimoto from the University of Tokyo gave an online talk on geometric nonlinear optical effects. First, he introduced topological states of matter and the notion of the Berry connection to the audience. He explained how these concepts lead to the quantization of observable quantities in the linear-response regime so that the audience learned the background to understand his main research works. After the introduction, he talked about several geometric nonlinear effects in topological states beyond the linear response theory. In particular, the shift current stems from the geometric nonlinear response, and the quantized circular photogalvanic effect can be realized in specific Weyl semimetals. In addition to the theoretical concepts, he also discussed experimental observations, such as perovskite-based solar cell materials and chiral multifold fermion compound RhSi. During and after the talk there were interactive discussions, and more than 25 participants attended this well-presented talk. -Chen-Hsuan Hsu and Ching-Kai Chiu

2021-03-16

Award

## Dr. Jeffery Fawcett received 12th annual RIKEN Research Incentive Award (Ohbu Award)

Jeffery Fawcett received "FY2020 Researcher Incentive Award (桜舞賞)" on March 17, 2021 for his achievements in the "Study of genome evolution using large-scale genomic data". Congratulations!

2021-03-12

Press Release

## The future may come when each of us can carry around a black hole as information storage device

-- Imagining and prototyping future information storage devices based on scientific theories.-- The first prototype of the Useless Prototyping Studio, "Black Hole Recorder," has been completed and is now on display at the National Museum of Emerging Science and Innovation from March 14 (Sun.) to 21 (Sun.), 2021. The "Useless Prototyping Studio", which uses seemingly useless prototypes to visualize the possibility that curiosity about the unknown can create the future, has created its first prototype, the "Black Hole Recorder," a future information storage device. The outline and background information are available on a special website released today, March 12. In addition, as an opportunity for the general public to view the recorder, it will be exhibited at the National Museum of Emerging Science and Innovation (Miraikan) in Koto-ku, Tokyo, from March 14 (Sunday), the birthday of Albert Einstein and the death anniversary of Stephen Hawking, the two scientists who developed the basic theory of black holes. The Black Hole Recorder is a prototype black hole storage device developed with an eye to the future where black holes can be controlled and used as a device to store information. Based on the motif of a phonograph, it implements a device that can record huge amounts of data. In addition to storing large amounts of information, it is also capable of retrieving the information it has captured. Since the invention of writing thousands of years ago, humans have evolved the media and technologies for recording information from paper, printing, photography, phonograph, video, and data. In recent years, developments have been made to see how large a quantity of information can be stored. And in the future, we can think of the possibility of a time when black holes can be used as information storage and carried around in our pockets.

2021-03-12

Hot Topic

## iTHEMS NOW & NEXT FY2020

The annual in-house gathering entitled iTHEMS NOW and NEXT FY2020 was held on March 11th via zoom. The gathering is the occasion we share the current status and future perspectives on our research and organization. In the morning, keynote overview talks were given by Takashi Okada, Hiroyasu Miyazaki, Akinori Tanaka, and Ching-Kai Chiu, followed by the interdisciplinary talk which Don Warren and Catherine Beauchemin jointly presented. During subsequent lunchtime, a special session on the proper practices in conducting scientific researches was taken place. In the session, the participants discussed their research practices in small groups and later shared their discussions with all. The afternoon session was devoted to the progress reports from the working groups and the study groups. This time, we observed a moment of silence in honor of those affected by the 2011 Tohoku earthquake and tsunami during these presentations since it just marked precisely ten years from the calamity. Program Director Hatsuda's remarks concluded the gathering.

2021-03-11

Announcement

## Dr. Tetsuo Hatsuda's new book, "The Future of 'Useless' Research", will be published on April 9, 2021

Dr. Hatsuda's new book, "The Future of 'Useless' Research", will be published on April 9th, 2021. It is now available for pre-order!

2021-03-05

Seminar Report

## Quantum Matter Seminar by Prof. Jan Budich on March 3, 2021

We are happy to invite Prof. Han Budich from the Dresden University of Technology to give a talk on March 3rd. The topic is Exceptional Topology of Non-Hermitian Systems: from Theoretical Foundations to Novel Quantum Sensors. Prof. Budich started with the review of the topological phases. After the introduction, he introduced the emergence of the exceptional points from non-Hermitian systems. The exceptional points, which are similar to Weyl nodes, possess intrinsic topological properties. Later, he proposed a novel idea of the quantum sensor to probe topological features from non-Hermitian platforms. It is great to have this nice talk.

2021-03-04

Person of the Week

## Self-introduction: Yuta Sekino

I am Yuta Sekino, a JSPS fellow who joined iTHEMS on March 1, 2021. I am a theoretical physicist studying physics of ultracold atoms. My main research interest is universal properties of many-body systems as well as transport phenomena. I am currently working on atomic gases in spatially one dimension and spin transport. At iTHEMS, I hope to broaden my research horizon through discussions with researchers in various fields.

2021-03-04

Person of the Week

## Self-introduction: Takeru Yokota

My name is Takeru Yokota. I joined iTHEMS in March 2021. My research field is theoretical physics. I have been interested in the development of nonperturbative frameworks to describe many-body systems, such as the functional renormalization group (FRG). In particular, I have challenged to establish a new framework based on the combination of FRG and density functional theory, which is another powerful method used for various systems including nuclear systems and condensed matter systems, and involved in the application to electrons, nucleons, and classical liquids. I am looking forward to new developments of research emerged from the interaction with researchers from various fields in iTHEMS.

2021-03-02

Hot Topic

## Biology and mathematics: What it would be like to be crazy about both

Dr. Ryosuke Iritani (Research Scientist, iTHEMS) writes frankly on the website SURI-JOSHI about why he chose his current field. Don't miss it!

2021-03-02

Hot Topic

## Report on the online discussion, "The Usefulness of 'Useless' Knowledge"

On August 22 last year, academist.Inc, and RIKEN iTHEMS held an online discussion entitled "Tetsuo Hatsuda × Yoshinori Ohsumi × Sayaka Oki Online Discussion: The Usefulness of 'Useless' Knowledge" with the aim of discussing the future of basic science research. Please refer to the RELATED LINKS for the online discussion of the day.

2021-03-01

Research News

## RIKEN RESEARCH: Supernova had a missing companion star

The massive star that exploded to form the supernova known as Cassiopeia A most likely had a companion star that has yet to be spotted, a spectro-scopic analysis by RIKEN astro-physicists suggests.

2021-03-01

Research News

## RIKEN RESEARCH: RIKEN and JAXA collaborate on real-time rainfall forecasts

Researchers from RIKEN, Chiba Univer-sity, the University of Tokyo and the Japan Aerospace Exploration Agency (JAXA) have used a combination of satellite data and supercomputer simulations to offer five-day rainfall forecasts over the Internet covering the globe. Dr. Takemasa Miyoshi (iTHEMS/R-CCS) commented in the article.

179 news in 2021