# News

118 news in 2019

2019-12-19

## iTHEMS end-of-the-year party, farewell party, and birthday party !

iTHEMS end-of-the-year party + farewell party for Nagisa Hiroshima + birthday party for members who was born in December was held from 15:30- on Dec.13, 2019. Before the start of the party, Nagisa who is leaving iTHEMS to become an assistant prof. at Toyama Univ. gave a 15 min. talk on the current status of Dark Matter (DM) Search and also on the activities of the iTHEMS DM Working Group. Her final conclusion was that DM would be a key scientific problem related to all iTHEMS Research Cells, i.e. Extreme Universe, Life & Evolution, Future Geometry, and Mathematics & AI. The room was full of researchers who are interested not only in dark matter but also in beautiful cakes, fruits, foods and in interesting conversations. Many thanks for iTHEMS secretaries who prepared for the wonderful party and thanks also to the people who brought sweets from all over the world!

2019-12-19

## Report of Young Researcher Association for Biological Rhythms 2019

Young Researcher Association for Biological Rhythms 2019, supported by RIKEN iTHEMS, was held at Kyushu University on December 7-8. In biology, there are many rhythmic phenomena, such as, circadian clocks, cell cycles, metabolic oscillations and so on. This research workshop has been a good opportunity for young researchers to get together and discuss wide field of biological rhythms. There were 6 invited lectures. The invited lectures contained various topics on biological rhythms: insulin oscillations, circadian clocks of insects, chronopharmacology, methylation cycles, mathematical biology, and cyanobacterial circadian clocks. Because these research topics attracted many participants, we enjoyed active discussions until late at night.

2019-12-18

## Math seminar talk by Dr. Wahei Hara

The iTHEMS Math seminar was held on 4 December, inviting Wahei Hara from Waseda university. The title of the talk was “Noncommutative crepant resolutions and some higher dimensional flops”. The central topic was singularities of algebraic varieties and representation theory. In the first part, the speaker explained the McKay correspondence as an example of connections between du Val singularities and representation theory of finite subgroups of the special linear group of degree two over the complex number field. In the second part, the speaker talked about noncommutative crepant resolutions of singularities. There are several ways to interpret the Mckay correspondence. The derived McKay correspondence is the interpretation of the McKay correspondence in terms of derived categories. The notion of noncommutative crepant resolutions is the generalization of the derived McKay correspondence to a large class of singularities. We discussed applications of noncommutative resolutions to the study of derived categories in birational geometry.

2019-12-18

## Blasts from the past, article on RIKEN Research with reference of iTHEMS Researchers

The evolution of an exploding star begins more haphazardly than previously thought. Reference: Ferrand, G., Warren, D. C., Ono, M., Nagataki, S., et al.

2019-12-16

## Solving the Riddle: History of the Universe and Elements

Author: Shinya Wanajo Language: Japanese

2019-12-12

## DMWG Seminar by Dr. Chiaki Hikage

2nd IPMU-iTHEMS DMWG seminar was held on Dec. 12 at IPMU. Dr. Hikage gave a talk about the weak lensing cosmology by Subaru Hyper Suprime-Cam(HSC) survey. The weak lensing measurement is a powerful tool to probe the matter distribution in the Universe up to redshift z~2. Lots of galaxies are seen in the optical wavelength and the seeing of HSC is fine enough to determine the shape of the galaxy. When massive objects (i.e., dark matter halos and so on) lie on our lines-of-sight, the image of the background galaxies is distorted in a specific pattern. Photometric data of the HSC enables us to tomographically derive the map of the integral of the matter density. This quantity is referred to as the "shear". The power spectrum of the shear map leads to the cosmological parameter such as the total matter density. HSC has revealed that the matter density is in 10-30% of the total energy density of the Universe and previously claimed tension of the cosmological parameters between the measurements may not exist. With future HSC observations, a much precise and deep understanding of the matter distribution in our Universe should become available.

2019-11-29

## All-RIKEN Workshop on Virtual Reality holds second session

The first All-RIKEN Workshop on Virtual Reality held an introductory session in October. Many visitors came to try out VR and assess whether they could use it for their own research. On Tuesday, November 26, the second session of the workshop took place. iTHEMS members Don Warren and Gilles Ferrand hosted the all-day, hands-on event. The two primary goals were (1) to teach attendees how to use Unity, the engine Gilles and Don use for their own VR demo, and (2) to let them get their own data into a 3-D visualization. In the first part of the day, participants created their own computer game, entirely from scratch. (If you know someone who attended, ask to play their game!) This introduction to game design showed people how Unity works, and prepared everyone for the second half of the schedule. In the second half, they learned about what kinds of data can be visualized in 3-D and in VR. They also got to use a basic visualization kit (developed by Gilles) to explore their own data in 3-D. There was a lot of good discussion about how to present data in a way that works for 3-D and VR -- some formats that work very well on paper do not translate well to 3-D space! By the end of the workshop, attendees had the tools needed to start exploring their own data. Gilles and Don hope that they will continue to think about this, to develop their skills in Unity, and to form a 3-D and VR visualization community at RIKEN.

2019-11-25

## Introduction of Hallatschek group and daily activities: Berkeley Report from Dr. T. Okada

Hi, everyone! In this short article, I will write self-introductiton, also about the laboratory I am belonging to at UC Berkeley and also write my daily activities there. My research interest is theoretical biology, including biochemical reactions, biological networks, evolutionary dynamics etc. I am currently working at Hallatschek laboratory as a long-term visitor, and mainly researching on theoretical aspects of evolutionary dynamics there. As a theorist, one of ultimate goals is to predict outcomes of evolution. Since evolutionary processes are very complicated even under well-controlled conditions, this project is very difficult, but, at the same time, very attracting theoretically. Hallatschek lab studies evolutionary biology both experimentally and theoretically. There are approximately 10 members (students and postdocs) in total, and a half of us do evolutionary experiments using microorganisms, such as yeast and E. coli, and a half of us (including me) study theoretical stuff. For now, I have three meetings in the group every week. The attached photo is one of the weekly meeting which I am doing with Jonas (postdoc, left) and Stephan (graduate student, right). I am very satisfied with the scientific atmosphere here, and I really appreciate the support by iTHEMS. Also, I think that in evolutionary biology, there are many topics that are interesting for many mathematicians and physicist, and I am looking forward to interacting iTHEMS members when I come back to Japan.

2019-11-22

## Cooperative agreement formed between Nara Women's Univ. and iTHEMS

iTHEMS has exchanged a cooperative agreement with Faculty of Science and Faculty of Human Life and Environment, Nara Women's Univ. (NWU), to promote gender diversity in Science. The picture shows the signing ceremony held on Nov.11 at NWU: Tetsuo Hatsuda from iTHEMS (left), Prof. T. Watanabe from Dean of Faculty of Science (middle) and Prof. M. Takada from Dean of Faculty of Human Life and Environment (right). NWU is one of the two national women's universities in Japan and was founded 110 years ago on 1908. Currently, 21%(Math.), 10%(Bio.) and 13%(Phys. and Chem.) of women's Master students in Japanese national universities are produced from NWU. As a first joint effort between iTHEMS and NWU, RIKEN researchers will deliver a series of lectures "Frontiers in mathematics, universe, matter, life and information" from the fall of 2020 for the 1st and 2nd year undergraduate students in NWU. The lecturers on 2020 are Tetsuo Hatsuda (iTHEMS, nuclear physics), Yuka Kotorii (AIP/iTHEMS, mathematics), Shigehiro Nagataki (CPR/iTHEMS, astrophysics), Makiko Nio (RNC, particle physics), Ryosuke Iritani (iTHEMS, biology), Ai Niitsu (CPR, chemistry), Shigenori Otsuka (R-CCS/iTHEMS, meteorology) and Emi Yukawa (CEMS, information).

2019-11-22

## Discovery of teraelectronvolt photons from gamma-ray bursts: A new window for exploring the most luminous explosions in the Universe

On January 14, 2019, TeV gamma rays (photons with energies a trillion times that of visible light) were clearly detected for the very first time from a gamma-ray burst (GRB; dubbed GRB 190114C) by the MAGIC telescopes. The very high energy of the individual photons as well as the high power of the total signal demonstrate that they must be produced by a physical process that is distinct from the previously known afterglow synchrotron radiation. Combined with extensive multiwavelength data obtained by a large number of observatories from the radio to GeV bands, the most likely mechanism is judged to be "inverse Compton” radiation associated with the afterglow, whereby some synchrotron photons are significantly boosted in energy by colliding with high-energy electrons [1]. These findings were reported in two papers published on Nov. 21 in the journal Nature, one authored by the MAGIC Collaboration where Susumu Inoue of iTHEMS is the first corresponding author [2], and the other co-authored by a large team of astronomers including the MAGIC Collaboration [3]. Caption for the figure: Spectra of GRB 190114C in the X-ray to TeV gamma-ray energy range during two time intervals (top: 68-110 seconds after the beginning of the GRB; bottom: 110-180 seconds ibid.). Markers reflect data: white circles are observed MAGIC data; orange circles are MAGIC data corrected for intergalactic propagation effects. Curves are theoretical models: thin solid curves are synchrotron emission and inverse Compton emission shown separately; thick blue curves are their sum; dashed curves are inverse Compton emission when neglecting internal absorption effects.

2019-11-20

## Math Seminar talks by Dr. Atsushi Ito

The iTHEMS Math seminar was held on 8 Nov., inviting Atsushi Ito from Nagoya university. The title of the talk was "Some topics in projective geometry of algebraic varieties". The main subject of the talk was the Gauss map and the dual variety of an algebraic variety, which reflect the behavior of the tangent spaces at a moving point of the variety. In the first part, the speaker explained the duality theorem of the dual variety and the original variety, which holds in the usual setting but fails in the unusual (that is, in positive characteristic) setting. In the second part, we considered the dimension of the dual varieties. The main result says that the gap of the dimension of the dual variety from the expected dimension is determined by a fibration structure of the variety with a good fibres.

2019-11-19

## Article about iTHEMS on Journal of the Mathematical Society of Japan

Professor Takashi Tsuboi, Deputy Program Director of iTHEMS posted an article about RIKEN iTHEMS on Journal of the Mathematical Society of Japan. See the article in the November issue from the following link.

2019-11-19

## International WS "Collaborative Meeting on Supernova Remnants between Japan and USA" was held at RIKEN Wako campus and SUURI-COOL Kyoto

An international WS "Collaborative Meeting on Supernova Remnants between Japan and USA" was held at RIKEN Wako campus (Nov. 7-8, 2019) and SUURI-COOL Kyoto (Nov. 11-12, 2019) with Masaomi Ono (ABBL/iTHEMS), Shiu-Hang Lee (Kyoto Univ.) and Shigehiro Nagataki (ABBL/iTHEMS) as organizers. The aim of this workshop was to bring together experts including young researchers on supernova remnants and other related topics, such as supernovae, progenitor stars, and neutron stars, for active discussion and to initiate possible collaborations among the participants. In both 1st and 2nd weeks, there were about forty participants. Experts from USA mainly on supernova remnants gave excellent talks from both aspects of theories and observations. Not only supernova remnants but also many other related topics were presented by participants from Japan and Taiwan including students. During the workshop, many possible future collaborations were intensively discussed.

2019-11-13

## Self-introduction: Hidetoshi Nishimori

I am a Professor at the Institute of Innovative Research, Tokyo Institute of Technology. I obtained my degrees, BSc, MSc, and DSc, from the Department of Physics of the University of Tokyo. After a stint as a postdoctoral fellow at Carnegie-Mellon University and Rutgers University in the United States, I returned to Japan and have been working at Tokyo Institute of Technology, mostly at the Physics Department but I recently moved to the Institute of Innovative Research as the head of the Quantum Computing Research Unit. My main interest has been the theory of spin glasses, a typical hard problem of equilibrium statistical mechanics, especially exact results derived by using a special type of symmetry. I am recently more interested in quantum annealing, a quantum-mechanical paradigm to solve combinatorial optimization problems, a typical example of which is the ground-state search of spin glasses. This is a very exciting field not just because of the big attention from the society to quantum computing in general, but also due to the very interdisciplinary characteristics of the field in that very basic theoretical results are sometimes immediately implemented in real devices, typically the D-Wave quantum annealer, thus affecting the performance of the device in real-world industrial applications. I hope the stimulating environment of iTHEMS to further broaden the scope my research activities, leading to unexpected developments that are hard to be achieved elsewhere.

2019-11-13

## iTHEMS Public Lectures at RIKEN Kobe Open Campus 2019

iTHEMS Public Lectures were held at the 8th floor of the RIKEN IIB building on Nov.9 as a part of the RIKEN Kobe Open Campus 2019. Takumi Doi (RNC/iTHEMS) and Emiko Hiyama (Kyushu U./RNC) gave lectures on computational nuclear and particle physics. Takumi introduced the history and concept of computers with full of Kansai jokes, followed by an explanation of the recent results from massive parallel computers such as the K computer. Emiko explained why quantum systems with more than 3 particles are fundamentally different from the two-body systems, and how to overcome the difficulty by computational approach. Both lectures were pedagogical enough for non-scientists and stimulated interesting questions from the audience.

2019-11-11

## Self-introduction: Takashi Sakajo

I am a full professor of Department of mathematics at Kyoto University, and a project professor of Liaison Center in Mathematics in RIMS at Kyoto University. From Nov. 2019, I am appointed to a senior visiting scientist at RIKEN iTHEMS. My educational background in undergraduate/graduate courses at Kyoto University was mathematics, but I have been keeping strong interests in the other fields of sciences. My expertise in research is applied mathematics, especially mathematical fluid dynamics, in which I would like to understand highly nonlinear and complex fluid phenomena observed in the evolutions of incompressible fluid motions from mathematical points of view theoretically as well as numerically. In addition to those academic topics, I am keen to conduct many interdisciplinary studies with people from the other disciplines (meteorology, medical, material science etc.) and industries. I am the chief coordinator of Math Clinic at MACS program in Kyoto University. These interdisciplinary activities are not just for applying existing mathematical theories, but for exploring new future problems for mathematical sciences from modern world. I am very happy to be a member of iTHEMS, where I can share the same interests with the members. Research Topics: • Topological Flow Data Analysis • Dissipative weak solutions of the Euler equations and turbulence theory • Vortex dynamics • Flow control of vortex dominated flows • Singularity formation and long-time behavior of vortex dynamics • Applied and computational complex analysis (ACCA) • Uncertainty Quantification (Data Assimilations) • Interdisciplinary Studies (Meteorology, Medical, Industrial problems)

2019-11-08

## iTHEMS Coffee Meeting continues

Every Friday, we have iTHEMS coffee meeting from 12:30, where somebody is asked to give a 15 min. lecture on a specific topic for non-experts by using our jumbo blackboard. On Oct.25, 2019, Ivan Kostov (CEA-Saclay) gave a 15 min. lecture on integrability in quantum field theory by drawing s multi-particle scattering diagram for elementary particles living in 2 space-time dimensions. On Nov.1, 2019, Pascal Naidon (RIKEN Nishina Center) gave a 15 min. lecture on the quantum physics of Efimov effect by using his handmade Borromean rings (three entangled ribbons which is a classical analogue of the Efimov effect).

2019-11-07

## Two Senior Visiting Scientists jointed iTHEMS

It is our great pleasure to announce that two Senior Visiting Scientists have joined iTHEMS from Nov.1, 2019. Prof. Takashi Sakajo (Kyoto Univ.) whose research fields are applied mathematics and mathematical fluid dynamics. He is in charge of the SUURI-COOL Kyoto. Prof. Hidetoshi Nishimori (Tokyo Institute of Technology) whose research fields are statistical mechanics and quantum computation. He is one of the founding members of the iTHEMS QCoIn working group.

2019-11-01

## Math Seminar talks by Dr. Ken Shiozaki

The iTHEMS Math seminar was held on 24 Oct., inviting Ken Shiozaki from Kyoto university. The title of the talk was "Atiyah-Hirzebruch spectral sequence in band theory". The main subject of the talk was topological K-theory, a branch of topology in mathematics, from the viewpoint of physics. In the theory of condensed matter physics, it is well-understood that a classification of topological phases is given by topological (twisted equivariant) K-theory. Conversely, some physical intuitions help us understanding (or even calculating) K-theory. In the talk, the speaker illustrated "physical meanings" of basic mathematical notions such as the axioms of cohomology theory, the Mayer-Vietoris exact sequence and the Bott periodicity.

2019-10-30

## The modelling work on supernova remnants made at ABBL & iTHEMS is highlighted in the latest image release from NASA's Chandra observatory

On October 17 the Chandra X-ray Observatory released an updated image of the supernova remnant known as Tycho. Supernova remnants, the aftermath of a stellar explosion, are key to understand how stars end their lives, and how physical elements are synthetized and distributed in the galaxy. The new image, besides being visually striking, contains important clues to understand the explosion physics. Two papers are introduced in the text of the image release. The first paper, Sato et al 2019 (Genus Statistic Applied to the X-ray Remnant of SN 1572: Clues to the Clumpy Ejecta Structure of Type Ia Supernovae), used a new image analysis technique to mathematically characterize the clumpiness of the ejecta. The second paper, Ferrand et al 2019 (From the supernova to the supernova remnant: the three-dimensional imprint of a thermonuclear explosion), presented 3D numerical simulations made from a physically-motivated supernova explosion model. Both works conclude that part of the irregularities visible on the image, at an age of about 450 yr, were actually present from the very beginning. The two teams are now collaborating on the image analysis for the comparison of observations with models. Related work is also on-going with other colleagues at Rikkyo University. The 3D printed model on the photo was made from G. Ferrand's simulations. Credit: RIKEN/G. Ferrand, et al & NASA/CXC/SAO/A. Jubett, N. Wolk & K. Arcand

2019-10-30

## Math Seminar talks by Professor Masaki Tsukamoto

Professor Masaki Tsukamoto of Kyushu University, the winner of 2019 Geometry Prize of the Mathematical Society of Japan, visited iTHEMS for October 21 - 23 and gave a series of talks at Math Seminar. The theme of his talks was `Mean dimension of dynamical systems and information theory'. On October 21, 15:30-16:30, 16:40-17:40, he gave survey talks at Okochi Hall; In the first part he explained the notion of mean dimension in relation with information theory as an obstruction to embedding dynamical system to the shift on the Hilbert cube. In the second part he explained the notion of mean dimension in relation with data compression and showed that the mean dimension is obtained by applying to a (mini-max) variational principle to the dynamical rate distortion. His talks on October 22 and 23, 13:30-14:30 at the room 435-437 were on the key observation concerning the embedding problem and that on that concerning the dynamical rate distortion, respectively. The participants enjoyed his clear explanations on this mean dimension defined by Gromov which can play important role in the future study of infinite dimensional dynamical systems.

2019-10-25

## KUIAS-Heidelberg-iTHEMS joint WS was held at SUURI-COOL Kyoto

KUIAS-Heidelberg-iTHEMS joint WS "Mathematical Sciences and Medicine" was held at SUURI-COOL Kyoto on Oct. 10, 2019 with Motomu Tanaka (Heidelberg/KUIAS) and Tetsuo Hatsuda (iTHEMS) as organizers. The main aim of this workshop was to exchange ideas to create new paradigm in clinical medicine with the help of physicists, mathematicians and biologists. After the welcome address by Shigefumi Mori (Director General of KUIAS, Kyoto Univ. and Science Advisor of iTHEMS), there were 10 talks by the physicists, mathematicians and biologists from Heidelberg Univ., Kyoto Univ., Doshisha Univ. and RIKEN. Each talk was very stimulating and created lively discussions under relaxed atmosphere of SUURI-COOL Kyoto Office. To continue the discussions, we decided to have another meeting in the near future with active participation of medical doctors in Kyoto and Heidelberg.

2019-10-24

## Two conferences at Berkeley - Berkeley Report from Dr. K.Mikami

MSRI holds a semester program “Microlocal Analysis” in fall 2019. I fortunately attend this program while my stay at University California Berkeley (UCB) via iTHEMS-UCB math young visiting scholar program. There were two conferences on microlocal analysis in the third week of October. From October 14 to 18, there was a conference entitled “Recent Development in Microlocal Analysis”. It consists of 18 talks on various kinds of topics on microlocal analysis by specialists from all over the world. They contain some topics which is very closely related to my research works, such as observability and semiclassical measure. In October 19 and 20, there was a conference entitled “Microlocal Analysis and Spectral Theory: A Conference in Honor of Richard Melrose”. Richard Burt Melrose is an Australian mathematician who is famous for his broad research on microlocal analysis and geometry. The speakers include two fields medalists, Terence Tao and Akshay Venkatesh. Over all, there were around 30 talks(!) in a single week. Though it was a bit tight schedule, all talks were really nice and inspiring. Lastly, it was my great honor to attend these great conferences.

2019-10-24

## DMWG Seminar by Dr. Toyokazu Sekiguchi

The 2nd DMWG seminar was held on Oct.21, inviting Dr. Sekiguchi from The Univ. of Tokyo/KEK. Focusing on the weakly interacting massive particle (WIMP) case, he lectured the formation of the minimum mass DM halo in the early Universe and its implications. WIMP is one of the strongest candidates for DM. From a theoretical point of view, neutral wino in the split-SUSY scenario is an example. One important feature of WIMP is that it achieves the current DM density, usually referred to as the relic abundance, via the so-called freeze-out mechanism. In the early Universe, the thermal equilibrium between WIMPs and the standard model (SM) particles is maintained. As the Universe expands, the temperature decreases then the WIMP annihilation rate to the SM particles becomes smaller than the expansion rate of the Universe. At this point, the number density of DM is fixed. This is the thermal freeze-out mechanism to determine the DM relic density. However, the WIMP and the SM particle are still kinetically coupled even after the thermal freeze-out. In this stage, they transfer momentum by each other through the direct scattering. By carefully calculate the epoch of the kinetic decoupling, the minimum halo mass, which is important in characterizing the DM halo properties and the observable signatures, are determined. He showed that the minimum halo mass should be of the order of O(1e-7) solar mass when we consider the neutral wino in the split SUSY scenario. This value is smaller than that expected when we neglect the kinetic decoupling effect. Furthermore, the total number of small-scale halos resides in the larger halo increases. The enhancement in the number of small-scale halos leads to a higher flux for gamma-ray annihilations in present-day halos. We have an increased possibility of detecting DM signatures in the on-going and planned astrophysical observations.

2019-10-10

## iTHEMS researchers host All-RIKEN VR Workshop

Virtual reality is a useful tool for exploring and presenting 3-D data because your brain is naturally tuned for interpreting the 3-D world. Experiencing the data in 3-D rather than on a 2-D screen takes advantage of these tunings. And, of course, it makes for a very memorable presentation of data, both to scientists and to the public. iTHEMS researchers Gilles Ferrand and Don Warren hosted an all-RIKEN workshop on virtual reality on October 7. This workshop drew nearly 30 people from RIKEN and beyond. Almost everybody studied something other than astrophysics. Most people were not iTHEMS members. Several were not researchers! Attendees learned about the VR project that Gilles and Don have worked on for two years, and got to explore data using VR headsets. The goal of the workshop was to build a community of researchers with a shared interest in VR. And, as Nathan Shammah demonstrated, any time you put scientists in a room together you can get discussion about their work. We hope that continued discussion of VR leads to more discussion of personal research, and maybe even new interdisciplinary projects! If you missed the first workshop, but would like to join Gilles and Don for the second workshop (a day-long, hands-on experience to learn about the VR demo and teach you how to develop software for VR), send Gilles or Don an email.

2019-10-09

## iTHEMS Colloquium given by Professor Yasuyuki Kawahigashi

iTHEMS Colloquium was held on 4 Oct. 2019, inviting Prof. Yasuyuki Kawahigashi from the University of Tokyo (he is also a senior visiting scientist of iTHEMS). The title was "Topological phases of matter and operator algebras", and he explained his researches on operator algebra and their relations with theoretical physics. The central subject of the talk was modular tensor category (MTC). A subfactor (an inclusion of simple von Neumann algebra) has the symmetry of a tensor category, in an analogous way to the Galois theory of fields. MTC is an important class of tensor category having an interesting commutativity of the tensor product, and is also a useful tool to describe the anyonic statistics of quasi-particles. A powerful source of MTC is conformal field theory, and a comparison of two mathematical approaches (conformal net and vertex operator algebra) is a recent hot topic. In this talk Prof. Kawahigashi displayed three interesting examples in which a mathematical research, originated from its own motivation, helps the study of mathemtaical physics later. The first is a conjecture by Lan-Wang-Wen about the mathematical formulation of gapped domain wall, which is rejected by a knowledge in subfactor theory. The second is alpha-induction in the theory of MTC, which is now understood as a mathematical formulation of anyon condensation. The third is a work by Bultinck et. al. on tensor network, which turned out to be parallel with the subfactor theory (such as tube algebra and flat connection) studied by Ocneanu, Haagerup and Prof. Kawahigashi in 80-90's. Because the talk was organized coherently, we can enjoy a lot of topics in 90 minutes.

2019-10-09

## Enrico Rinaldi interviewed by RIKEN Research

RIKEN Research covers an interview with Dr. Enrico Rinaldi. See the article in the Fall issue (page 4 from the following link).

2019-10-03

## iTHEMS members are focused on KAGAKUDO 100 BOOKS 2019

iTHEMS members are focused on KAGAKUDO 100 BOOKS 2019. Please see the following link.

2019-10-02

## iTHEMS DM working group seminar by Dr. Rinaldi

iTHEMS DM working group, which aims to bridge the collider, direct, and indirect dark matter (DM) searches to obtain inclusive understandings of DM and develop new strategies for coming experiments, is launched this summer. The 1st seminar is given by Dr.Rinaldi on Oct. 1st. He talked about composite DM theory. DM is a massive component different from ordinary matters (usually referred to as baryons) in our Universe. The nature of DM is still a big mystery and many kinds of explanations are proposed. Composite DM scenario is motivated by the origin of the mass in the standard model physics. In the standard model, the strong interaction is responsible for the proton and neutron mass hence for the mass of baryons. Considering a similar situation in the dark sector, composites of dark fermions can be DM in our Universe. The dark and the standard model sector are connected through the interaction between the constituent fermions and the standard model particles. Composite DM itself has no direct connection to our sector. This explains the non-detection of DM in the up-to-date collider, direct, and indirect experiments. Also in this scenario, the self-interaction of DM is naturally introduced. Then, it could ameliorate the small-scale problem which appears in more traditional DM scenarios. Starting from the general introduction for composite DM, his recent work based on the lattice calculations for the signatures of composite DM is also introduced. Signals from composite DM could be detected in the near future. A series of seminars and workshops are being planned as the working group activity. Please join us!

2019-09-30

## Self-introduction: Enrico Rinaldi

I am Enrico Rinaldi, a part-time researcher in iTHEMS, who was previously a SPDR fellow in RIKEN BNL and Quantum Hadron Physics Laboratory. My expertise is Monte Carlo numerical simulations of quantum field theories, also known as Lattice Field Theory simulations, which use massively parallel supercomputers (CPU and GPU-based) around the world to solve the complex equations hiding the mysteries of particle physics. My research is focused on understanding high energy strongly-coupled gauged theories, in particular in the context of extensions of the Standard Model (SM) of particle physics, like Dark Matter physics or theories of Composite Higgs. New discoveries are hinging on the theoreticians’ ability to make predictions that can be tested by experimentalists, and that is precisely the my goal. I am also engaged in projects related to low-energy nuclear physics, for example calculating nucleon-nucleon interactions or nuclear form-factors directly from the theory of Quantum Chromo-Dynamics (QCD). Moreover, I have been working on matrix models to study the gauge/gravity duality conjecture with the aim of understanding the possible intriguing relation between gauge theories and quantum gravity. I am currently researching new Machine Learning (ML) approaches to physics, mainly based on the promising rise of generative models. The aim is to improve our ability to get access to multi-dimensional parametric distributions describing physical systems with specific models.

2019-09-26

## Report of iTHEMS Biology Seminar

iTHEMS Biology Seminar was held on September 13, inviting Prof. Hiroyuki Kubota (Kyushu University) and Dr. Yasufumi Uezu (NTT). The theme of this seminar is “mathematical biology in temporal waveforms.” Prof. Kubota revealed that the temporal patterns of blood insulin concentration selectively regulate downstream molecules depending on network structure and time constant. His discovery is important for understanding the mechanism not only of insulin signaling but also of many signal transduction systems in biology. Dr. Uezu is specialist of voice production research. Textbook in this field often explains vocal fold vibration (sound source) and vocal tract filter are independent. In contrast, he experimentally showed that nonlinear interaction between them is crucial for generating various singing voice, for example falsetto and scream. The seminar attracted a wide range of audience including biologist, physicist, and mathematician, and we enjoyed active discussion.

2019-09-20

## Short Report of Robotics Workshop held at IIAS in Kyoto

Robotics Workshop organized by RIKEN was held on Sep. 12-13 at a beautiful campus of the International Institute for Advanced Studies (IIAS) in Kyoto. Gilles Ferrand (ABBL/iTHEMS) and Tetsuo Hatsuda (iTHEMS) attended the workshop: Gilles gave a talk on "Virtual Reality and Robotics" and also conducted VR demo during the coffee breaks with Tetsuo as his assistant. All the 35 talks during the two days were "graphically recorded" in real time as the one attached for the Gilles case. (Some illustration company in Kyoto came to do this.) Although each coffee break was short (5-10 min), altogether six people could enjoy the VR of the supernova remnant. It was an interesting experience for us to interact with robotics engineers who have rather different way of thinking from the researchers in basic sciences.

2019-09-20

## Knowledge that spreads from many encounters - Dr. Ade Irma Suriajaya

Dr. Ade Irma Suriajaya (Chacha) is originally from Indonesia and shifted her field from aeronautical engineering to mathematics. We will introduce the beauty of mathematics, which Chacha has been eager to learn, going so far as to move from Indonesia to China and then onto Japan.

2019-09-17

## Tracking down the origin of photons in gamma-ray bursts, article on RIKEN Research by Drs. S. Nagataki & D. Warren

The photons released by long gamma-ray bursts - the most powerful electromagnetic phenomena in the Universe - originate in the photosphere, the visible portion of the ‘relativistic jet’ emitted by exploding stars, according to simulations by RIKEN researchers.

2019-09-17

## The shape of circadian rhythm, article on RIKEN Research by Drs. S. Gibo & G. Kurosawa

The waveforms of circadian cycles in bacteria, flies and mammals become increasingly jagged as the temperature rises, two RIKEN researchers have predicted. This finding is a step toward solving the mystery of how circadian rhythms remain consistent under changing conditions.

2019-09-12

## QCoIn Seminar given by Dr. Hirotaka Irie

On Sep. 2 and 3, Dr. Hirotaka Irie (DENSO Corporation / iTHEMS visiting scientist; see his self-introduction in this volume of NewsLetter) gave a series of comprehensive lectures on "Quantum Annealing" which is a quantum computational scheme for hard optimization problems. This was held as a part of the iTHEMS QCoIn WG activity. In the first day, he started the lecture by explaining the fundamental notions of quantum computation and quantum annealing, followed by the basic usage of quantum annealer. In the second day, he discussed the notion of computational complexity in detail, and then showed various examples of the real-world applications of quantum annealer. The lectures were given only by using white-board with detailed explanation of basic equations, which stimulated lots of questions from the audience. Discussions continued during the break and after the lectures.

2019-09-12

## Self-introduction: Hirotaka Irie

I am Hirotaka Irie, a research scientist in quantum computing team of DENSO Corporation. From this summer of 2019, I also became a visiting scientist here at RIKEN iTHEMS. I received my Ph.D. in Physics (string theory) at Kyoto University in 2008, and worked as postdoc in KEK, National Taiwan University, National Center for Theoretical Physics (NCTS, Taiwan), and Yukawa Institute for Theoretical Physics (Kyoto University), where my research focused on non-perturbative aspects of string theory and mathematical physics. Now I joined DENSO Corporation, working toward real-world applications of quantum mechanical computing machines with combining aspects of mathematical physics and string theory. In fact, recent industrial studies also require highly sophisticated physical and mathematical researches. Here, I hope to discuss and collaborate with people in iTHEMS to jointly achieve new technological breakthrough which changes our daily life and society.

2019-09-10

## Lecture by Dr. Yuya Nakagawa from QunaSys

An Academic-Industrial Innovation Lecture was delivered by Dr. Yuya Nakagawa from QunaSys on September 4th. QuanSys is a venture company specializes in quantum computing and Dr. Nakagawa joined QunaSys shortly after having earned his Ph. D. In the first part, Dr. Nakagawa gave a concise overview of quantum computing. The second part of the lecture consisted of more detailed explanation including the result from QuanSys itself and the application to Quantum Chemistry. The lecture attracted audience not only from RIKEN but also outside RIKEN, especially notable companies. The last part of the lecture turned out to be filled with a lot of questions from the keen audiences, and candid comments were exchanged. We felt that the lecture is really serving as a hub that connects people from academics and industry.

2019-09-10

## Summary of the lecture of Introduction to quantum many-body system

A lecture on “Introduction to quantum many-body system “ by Prof. Hosho Katsura was held from September 5 to 6 at RIKEN. In particular, we studied basic concepts of many-body systems on lattices and how to investigate their properties in analytical and numerical ways. In the first part of the lecture, non-interacting Fermi and Bose systems on lattices were focused and we learned how to calculate energy bands. Such systems included Kitaev chain and Su-Schrieffer-Heeger model for one-dimensional fermions as well as free bosons describing low-energy properties of quantum magnets. In the second part, we studied spin systems such as Affleck-Kennedy-Lieb-Tasaki model from the perspective of frustration-free systems and the concept of matrix product states. The attendees were scientists from various backgrounds; physicists specializing in condensed-matter physics, atomic physics, nuclear physics, and particle physics as well as mathematicians. This lecture was filled with fruitful discussion and instructive to attendees who are not professional in lattice systems.

2019-09-04

## iTHEMS Program Director gave a talk at the 28th RIKEN Satosho Seminar

Program Director of iTHEMS, Prof. Tetsuo Hatsuda gave a talk at the 28th RIKEN Satosho Seminar on Aug. 29, 2019.

2019-09-04

## iTHEMS is focused on RIKEN NEWS

iTHEMS is focused on RIKEN NEWS. See the cover and the article on August issue (page 6 from the following link).

2019-09-04

## Genomic analysis of 370 Japanese Thoroughbred horses: the genetic background of why Thoroughbreds can run fast

Humans have been trying to improve Thoroughbreds by selectively breeding horses that can run fast. Each generation, a small number of males are selected to breed so that only these “elite” males can pass on their genes to the following generation. In this study, we examined how this continuous artificial selection has affected the evolution of the genomes of Thoroughbreds. First, we found that the genetic diversity is low in Thoroughbreds due to repeated inbreeding since even before the establishment of Thoroughbreds. Second, we found several regions that exhibit signatures of artificial selection. These regions typically show locally reduced genetic variation and should contain genes that are important for the athletic performance of Thoroughbreds. This study opens the way for genomic information to be utilized in the selective breeding of Thoroughbreds.

2019-08-30

## Gilles Ferrand was highlighted in a recent article of RIKEN RESEARCH "Supernova remnants used to probe how star explosion took shape"

RIKEN astrophysicists have bridged the gap between studies of supernova and those of their remnants by using the output of a supernova model as the input for a model of a supernova remnant. This approach offers a way to assess the validity of supernova models.

2019-08-22

## Math-Life Workshop was held at Hokkaido University

Math-Life Workshop, organized by iTHEMS (RIKEN), SACRA (Kyoto U.), AIMR(Tohoku U.) and MSC (Hokkaido U.), was held at Hokkado Univ. on Aug.19-20 with 66 participants. Dr. Ryosuke Iritani and Dr. Shingo Gibo from iTHEMS gave 1-hour invited lectures on mathematical ecology and chronobiology, respectively. Both lectures contain very nice introduction to these subjects followed by their own recent research topics. There were also 6 other lectures by the speakers from Hokkaido Univ., Kyoto Univ., Hiroshima City Univ. and Tohoku Univ. The workshop was very successful with full of stimulating discussions among mathematicians, physicists, biologists and life scientists.

2019-08-07

## Japan-Israel Workshop on HEA with Roger Blandford

During 18-23 July, a workshop to bring together experts on High Energy Astrophysics from Japan and Israel was held. The first part (18-19 July) was held in RIKEN Wako, while the second part (22-23 July) was held in RIKEN Kobe IIB. The workshop was supported by iTHEMS. This workshop was motivated by 3 things. One was Roger Blandford, a reviewer of iTHEMS AC, was planning to visit RIKEN Wako during 24-26 for the review. Second was Noemie Globus, who is a visitor of Astrophysical Big Bang Lab. (ABBL), was interested in organizing a meeting between Japan & Israel. She worked well as a Co-Chair of the meeting. Third was Hirotaka Ito (Chair, ABBL) has some collaborators in Israel, including Amir Levinson & Asaf Pe'er. We enjoyed lots of excellent talks both from Japan & Israel. Roger Blandford gave a talk on his interpretation of the black hole shadow image by the even horizon telescope (EHT). We had lots of discussions with Israel people, and we agreed to proceed our collaborations on long/short gamma-ray bursts. We received many emails from Israel people that they enjoyed the workshop and their stay in Japan very much, and some of them proposed to have a second meeting in Israel. Hirotaka Ito & Noemie Glogus worked very well as chairs of organizers. Thanks to them & iTHEMS, the meeting was very successful.

2019-08-05

## Lecture by Dr. T. Doi as a first event at SUURI-COOL (Kyushu)

As a research activity of RIKEN iTHEMS and Kyushu Univ. collaboration, Dr. T. Doi gave lectures on his research, Lattice QCD and research activity on HAL QCD collaboration from 31th July to 2nd Aug. In his lectures, approximately 25 persons who were mainly PhD students attended and had many discussion with him. It was very fruitful days for them.

2019-08-05

## Report of the workshop on "Math of Jets"

A workshop on "Math of Jets" co-sponsered by RIMS (Kyoto University) and iTHEMS was held from July 29 to 31 at Kyoto University. Researchers from wide scientific fields, such as, planetary atmosphere, astrophysics, quark-gluon plasmas, and so on gave talks. The common keyword for participants are 'jet' and/or 'hydrodynamics'. Since most of participants use numerical hydordynamic or magnetohydordynamic simulations as a tool for their study, some part of discussions are devoted to introduce numerical technique, numerical difficulties and unresolved problems. We enjoyed getting to know research topics and problems in other research fields. At the workshop banquet, one of participants said as a speech "Recently the borders between countries have not been so high but the borders between scientific field have been getting higher and higher, event if they have common language, for example, 'hydrodynamics' like us. We should continue this kind of workshop. Otherwise, we can not understand each other in near future." The workshop was good opportunity to interact with other fields and we hope we will have next meeting in near future.

2019-08-02

## Is your Supercomputer Stumped? There May Be a Quantum Solution

The recent paper by Jason Chang* (iTHEMS/UCB/LBNL), Shigetoshi Sota* (R-CCS) and their collaborators in US, "Quantum annealing for systems of polynomial equations" (Nature Scientific Reports, 9 (2019) 10258), was press-released on Aug.1, 2019 with a headline - Is your Supercomputer Stumped? There May Be a Quantum Solution - (*) Both Jason and Shigetoshi are members of the iTHEMS QCoIn Working Group.

2019-07-26

## iTHEMS Advisory Council (AC) is being held from July 24 (Wed.) through 26 (Fri.)

iTHEMS Advisory Council (AC) is being held from July 24 (Wed.) through 26 (Fri.). On July 25 (Thursday), short talks and poster presentations by iTHEMS researchers have been given, followed by stimulating discussions with the AC members in various different fields (mathematics, physics, astronomy, biology and engineering). Lively discussion continued during the breaks and poster sessions, with beautiful sweets and coffee/tea prepared by iTHEMS assistants. We are very grateful to the AC members who kindly came over to RIKEN Wako Campus to make precious suggestions about science activities and the management of iTHEMS.

2019-07-22

## Synthetic dimensions and topological chiral currents in mesoscopic rings

In condensed matter systems, the topological effect of chiral currents is intimately related to two-dimensional systems. Recently emerging concept of "synthetic dimensions" provides a way to explore two-dimensional physics using one dimensional setups by using internal degrees of freedom as an additional dimension. Synthetic dimensions have so far been predominantly developed in atomic and optical physics. In this work, we extend this concept to condensed matter systems of a mesoscopic ring coupled to a nanomagnet. Regarding the spin degrees of freedom of a nanomagnet as a dimension, we interpret a current in the ring, which is locked to the nanomagnet's spin, as chiral edge currents of a two-dimensional quantum Hall system. We thus provide a broader conceptual setting for synthetic dimensions, extending it to a rich domain of potential practical applications in condensed matter systems.

118 news in 2019