Seminar Report
337 news

20200124
Seminar ReportMath seminar by Dr. Shu Nakamura
The iTHEMS Math seminar was held on 23 January, inviting Shu Nakamura from Gakushuin university. The title of the talk was “Semiclassical methods in mathematical quantum mechanics”. The topic was semiclassical analysis and scattering theory of Schrödinger operators. In the first part, the speaker gave a introductory talk on the microlocal analysis and semiclassical analysis of Schrödinger operators. He started his talk by introducing a canonical quantization. Then he explained how canonical quantization is understood in the framework of semiclassical and microlocal analysis. Moreover he explained some recent results on this research field. In the second part, the speaker explained his recent results on scattering matrix of Schrodinger operators with long range potentials. At the beginning, he introduced the definition of scattering matrix and some known results. Then he stated his main result on the representation of scattering matrix. As an application, he gave some examples of long range potentials for which he proved several spectral properties of scattering matrix.

20200117
Seminar ReportMath Seminar by Prof. Syuji Yamamoto
The iTHEMS Math seminar was held on 17 December, inviting Shuji Yamamoto from Keio university. The title of the talk was “Multiple Zeta Values: Interrelation of Series and Integrals”. The topic was multiple zeta values (MZVs), which is a generalization of the values of the Riemann zeta function. In the first part, the speaker explained the definition of MZVs, and the statement of the Zagier conjecture, which predicts how many algebraic relations should exist among MZVs. Moreover, he explained several known algebraic relations, including Euler relation, Hoffman relation, duality, sum formula, Ohno relation, etc. He also provided two types of proof of duality, one of which is due to himself and Seki. In the second part, the speaker explained Double Shuffle Relation and Regularization. It is conjectured that these relations generate all the algebraic relations of MZVs, but this is a hard open problem. For example, it is unknown whether the relations imply duality. However, many relations are generated by these relations. The speaker explained some concrete examples, after introducing integral series identity.

20191218
Seminar ReportMath 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.

20191212
Seminar ReportDMWG Seminar by Dr. Chiaki Hikage
2nd IPMUiTHEMS DMWG seminar was held on Dec. 12 at IPMU. Dr. Hikage gave a talk about the weak lensing cosmology by Subaru Hyper SuprimeCam(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 linesofsight, 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 1030% 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.

20191120
Seminar ReportMath 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.

20191113
Seminar ReportiTHEMS 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 twobody systems, and how to overcome the difficulty by computational approach. Both lectures were pedagogical enough for nonscientists and stimulated interesting questions from the audience.

20191101
Seminar ReportMath 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 "AtiyahHirzebruch spectral sequence in band theory". The main subject of the talk was topological Ktheory, a branch of topology in mathematics, from the viewpoint of physics. In the theory of condensed matter physics, it is wellunderstood that a classification of topological phases is given by topological (twisted equivariant) Ktheory. Conversely, some physical intuitions help us understanding (or even calculating) Ktheory. In the talk, the speaker illustrated "physical meanings" of basic mathematical notions such as the axioms of cohomology theory, the MayerVietoris exact sequence and the Bott periodicity.

20191030
Seminar ReportMath 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, 15:3016:30, 16:4017:40, 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 (minimax) variational principle to the dynamical rate distortion. His talks on October 22 and 23, 13:3014:30 at the room 435437 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.

20191024
Seminar ReportDMWG 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 splitSUSY 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 socalled freezeout 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 freezeout mechanism to determine the DM relic density. However, the WIMP and the SM particle are still kinetically coupled even after the thermal freezeout. 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(1e7) 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 smallscale halos resides in the larger halo increases. The enhancement in the number of smallscale halos leads to a higher flux for gammaray annihilations in presentday halos. We have an increased possibility of detecting DM signatures in the ongoing and planned astrophysical observations.

20191009
Seminar ReportiTHEMS 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 quasiparticles. 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 LanWangWen about the mathematical formulation of gapped domain wall, which is rejected by a knowledge in subfactor theory. The second is alphainduction 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 8090's. Because the talk was organized coherently, we can enjoy a lot of topics in 90 minutes.

20191002
Seminar ReportiTHEMS 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 nondetection of DM in the uptodate collider, direct, and indirect experiments. Also in this scenario, the selfinteraction of DM is naturally introduced. Then, it could ameliorate the smallscale 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!

20190926
Seminar ReportReport 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.

20190912
Seminar ReportQCoIn Seminar given by Dr. Hirotaka Irie
On Sep. 2 and 3, Dr. Hirotaka Irie (DENSO Corporation / iTHEMS visiting scientist; see his selfintroduction 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 realworld applications of quantum annealer. The lectures were given only by using whiteboard with detailed explanation of basic equations, which stimulated lots of questions from the audience. Discussions continued during the break and after the lectures.

20190910
Seminar ReportLecture by Dr. Yuya Nakagawa from QunaSys
An AcademicIndustrial 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.

20190910
Seminar ReportSummary of the lecture of Introduction to quantum manybody system
A lecture on “Introduction to quantum manybody system “ by Prof. Hosho Katsura was held from September 5 to 6 at RIKEN. In particular, we studied basic concepts of manybody systems on lattices and how to investigate their properties in analytical and numerical ways. In the first part of the lecture, noninteracting Fermi and Bose systems on lattices were focused and we learned how to calculate energy bands. Such systems included Kitaev chain and SuSchriefferHeeger model for onedimensional fermions as well as free bosons describing lowenergy properties of quantum magnets. In the second part, we studied spin systems such as AffleckKennedyLiebTasaki model from the perspective of frustrationfree systems and the concept of matrix product states. The attendees were scientists from various backgrounds; physicists specializing in condensedmatter 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.

20190904
Seminar ReportiTHEMS 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.

20190805
Seminar ReportLecture by Dr. T. Doi as a first event at SUURICOOL (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.

20190718
Seminar ReportReport of iTHEMS colloquium  Spacetime Geometry of Black Holes, Wormholes, and Time Machines
General relativity tells us how spacetime is curved by energy distribution and how matter moves in the spacetime. Classical black hole, which is a solution of the classical Einstein equation, has the event horizon and singularity. Event horizon, from which anything cannot escape, is defined at infinite future, and physical quantities such as energy density diverge at the singularity. These properties are not physically acceptable. Then, what are black holes in our universe? Prof. PeiMing Ho (National Taiwan University) addressed this question by studying quantum effects in general relativity. The key is the nature of the vacuum. Classical matter always has positive energy, but in quantum field theory the expectation value of energy density can be negative due to quantum fluctuation of the vacuum. The semiclassical Einstein equation connects the expectation value of energymomentum tensor to the curvature of spacetime. If there is negative energy, traversable wormhole solutions can be constructed. They could be used as time machines for backward time travel, but they would lead to several paradoxes like “Grandfather paradox”. Prof. Ho explained this topic by showing how SF movies were inconsistent with physical laws. Then, he asked “What are the appropriate energy conditions to avoid inconsistencies?” The answer is still unknown, but it should be related to socalled “information paradox” in black holes. Suppose that a star (classical matter) collapses to a classical black hole. Hawking derived that the black hole evaporates slowly by emitting radiations due to the quantum properties of the vacuum. Then, where has the information of the matter gone after the evaporation? The information seems to disappear because the matter is trapped inside the horizon while the black hole evaporates. Any information must be preserved in quantum theory, but the mechanism is not clear in the black hole evaporation. As he said, one scenario is that some remnant is formed instead of complete evaporation. He first explained that, due to quantum fluctuation of the vacuum, the region near the wouldbe horizon is modified to obtain a “neck” structure without a horizon. The (proper) volume inside the neck is larger than the usual volume of the 3dimensional sphere with the radius of the neck (because of negative energy). This is like a SF apartment: when you enter a room, it has a larger space than you expected from the outside. This is one possibility of quantum black holes. He also discussed dynamics of the neck black hole. As it evaporates, the neck would shrink and the information inside the neck would be left as a remnant, but this seems to be not a good solution to the information problem because the information would be isolated from the exterior world forever. Finally, he introduced his recent progress: when a trapping horizon (a local and dynamical notion of horizons) becomes timelike, negative energy occurs and the blackhole mass decreases (not by Hawking radiation). It is a nonperturbative effect w.r.t. Planck constant, which could not exist in the classical limit. This result implies that the four factors are closely related: dynamics near quantum black hole, appropriate energy condition including quantum effects, a more proper description beyond the semiclassical one, and the mechanism of information recovery. His entertaining talk showed that a black hole is not just a hole but a window to a new world. It is time to ask again “What is black hole?”

20190704
Seminar ReportMath seminar by Hiroki Kodama
Hiroki Kodama had a seminar talk in the iTHEMS math seminar on 20 June. The topic was the foundation of metric space and its generalizations. Metric space is one of the most primitive setting of geometry. This notion is defined in an abstract way by metric function satisfying 3 axioms. Not only the Euclidean metric, which is familiar for all of us, many ideas arising all over the science (e.g. the distance of two DNAs) are formulated as a kind of metric. A main interest of this seminar was a generalization of metric space, which is less popular even for mathematicians. A function satisfying the axioms of metric space except for the symmetry axiom d(x,y)=d(y,x) is called an asymmetric metric (a typical example is the cost for a ship on a river to move from one point to another). In the first half of the talk, Kodama introduced the basic notion of (asymmetric) metric spaces with various examples. In the second half, he introduced an interest of asymmetric metric space by showing rich information it includes.

20190620
Seminar ReportSeminar by Dr. Allard van Marle from UNIST in Shouth Korea
Dr. Allard Jan van Marle visited ABBL and iTHEMS this week from his home institute of UNIST in South Korea. On Monday, June 17, he gave a seminar about his work in astrophysics, on particle acceleration and particleshock interactions. This is a very difficult topic to study because of the very different scales (length, time, and energy) involved. Lowenergy electrons and ions create the magnetic field turbulence that lets particle acceleration take place, so numerical simulations should resolve their motion. But accelerated particles have energies orders of magnitude higher, which means the numerical grid must be much larger to track them. Dr. van Marle presented a new numerical method that partially resolves this tension. This "particle in [MHD] cell" code averages out the majority of the lowenergy electrons/ions, freeing up computational resources to track the higherenergy particles that are of more interest to most astrophysicists. Shock fronts are everywhere in the universe, but they come in a large variety of speeds, sizes, and locations. The work presented by Dr. van Marle will help to determine how (or if) all of these different shocks behave as natural particle accelerators.

20190613
Seminar ReportSeminar by RIKEN researcher, Dr. Nathan Shammah
RIKEN researcher Nathan Shammah gave the first seminar for the QuCoIn (Quantum Computing and Information Science) working group. On June 13, he hosted an interactive workshop on opensource software and the Quantum Toolbox in Python (QuTiP) library. Opensource software, which allows anyone to see its source code, is becoming popular in business, in science, and among the general public: even tech giants like Microsoft and Google are investing in opensource projects. Python, in particular, is a highlydeveloped ecosystem with many packages, and one that most of you are probably already familiar with. The QuTiP code is one such package, which lets you simulate quantum systems, and even quantum circuits, on your (nonquantum) computer. About twenty people attended Nathan’s workshop and started learning to use QuTiP. We hope that this experience, and the new tool kit, will help people to accelerate their research and advance the field. If you have questions about QuTiP, please ask Nathan—he is very happy to discuss the software! And if you are interested in quantum tech research highlights, you can subscribe to Nathan's monthly newsletter on quantum technologies from the link below.

20190607
Seminar ReportSeminar by Professor Yasunori Nomura from Berkeley
Prof. Yasunori Nomura from Berkeley Center for Theoretical Physics, for which Prof. Nomura serves as the director, gave a seminar entitled " Quantum Mechanics of an Evaporating Black Hole" on June 6th. In his talk, he elucidated the socalled information paradox of evaporating black holes and plainly presented his resolution of this longstanding paradox. We are particularly pleased that we could invite Prof. Nomura not long after Coordinator Tada's own seminar at Berkeley. Frequent mutual visit between Berkeley and RIKEN would be most beneficial to iTHEMS, so we encourage all the iTHEMS members to find an opportunity to visit Berkeley, or invite somebody from there.

20190523
Seminar ReportReport of iTHEMS Special Lecture – How did the Universe Begin? Inflation Theory & Road to the Proof
On May 21st, iTHEMS Special Lecture by Dr. Katsuhiko Sato (Professor Emeritus, The University of Tokyo / Director, Research Center for Science Systems, Japan Society for the Promotion of Science) was given at Okochi Hall for more than 100 participants. Dr. Katsuhiko Sato is well known as a scientist who discovered the inflation mechanism of the early Universe in 1981. In the special lecture, Dr. Katsuhiko Sato gave an introduction about the expansion of the universe, mysteries about uniformity & isotropy of the universe, and absense of monopoles. Then Dr. Katsuhiko Sato explained how he got an idea of the inflation mechanism, motivated by SpontaneousSymmetryBreaking (SSB) mechanism (SSB was proposed by Dr. Yoichiro Nambu), and explained how these problems are solved by the Inflation mechanism. Dr. Katsuhiko Sato introduced about future missions that will prove firmly the inflation mechanism, including LiteBIRD that will measure Bmode in the polarization of cosmic microwave background in the universe. It was a great coincidence that JAXA announced on the same day, May 21st, that JAXA has made a decision to launch LiteBIRD. We wish the Inflation mechanism proposed by Dr. Katsuhiko Sato will be proved firmly in the near future.

20190516
Seminar ReportDr. Shunji Matsuura from 1QBit gave a series of lectures
Our visitor Dr. Shunji Matsuura from 1QBit, a startup company specializes in quantum computing and quantum information technology based in Vancouver, Canada gave a series of lectures from May 13 (Mon) through May 15 (Wed). Dr. Matsuura started with a basic explanation of qubits and their entanglement. Then, he moved on to explain various method employed in the field of quantum computing, such as Variational Quantum Eigensolver (VQE). His explanation was especially clear to physicists, since Dr. Matsuura’s background is string theory receiving his Ph.D. in string theory from the Perimeter Institute for Theoretical Physics and the University of Tokyo, and he used to conduct research at the Kavli Institute for Theoretical Physics (University of California, Santa Barbara), McGill University, Riken, YITP (Kyoto University), and the Niels Bohr Institute (University of Copenhagen). His current research focuses on the fundamental aspects of quantumenhanced optimization, such as error correction and speedup, which are also of interest to some iTHEMS members, and we are hoping a lot of fruitful collaborations between iTHEMS and Dr. Matsuura as well as 1QBit group in future.

20190509
Seminar ReportReport of iTHEMS colloquium  Quantum computing: current status and prospects
On April 25th, iTHEMS Colloquium featured Prof. Keisuke Fujii from Osaka University. Prof. Fujii has just moved to Osaka and started his laboratory for Quantum computing. Started with quoting Richard Feynman and went on to summarize the history of quantum computing. Then he gave a pedagogical explanation of the principle of quantum computing and the overview of the subject. Next, among over three hundred papers at Quantum Algorithm Zoo, he singled out Quantum Phase estimation as the most important Algorithm. Prof. Fujii explained the algorithm and told the audience that it has application to Prime factorization, Quantum Chemistry and Quantum simulation as well as Quantum linger system solver, which has relevance to AI. He then gave the assessment of the current status of quantum computing and future prospect. The lecture was concluded by the exposition of Quantumclassical hybrid algorithm and its application to machine learning. Because of the exciting topic featured, the lecture attracted many keen audience.

20190425
Seminar ReportiTHEMS public lectures at RIKEN Open Day
iTHEMS public lectures at the RIKEN open day on April 20, 2019, were held with an extreme success. The lectures are (1) Surprising Theorem of Gauss (Y. Kubota), (2) Mystery of Circadian Rhythm (G. Kurosawa), (3) Mechanism of Artificial Intelligence (M. Taki), (4) Coldest Place in the Universe (T. Ozawa), (5) What is Dark Matter ? (N. Hiroshima), (6) Evolution through Copy and Paste of DNA (J. Fawcett). Thank you all who have contributed to make this happen!

20190424
Seminar ReportReport on ZetaValue2019 Conference by Chacha (Dr. Ade Irma Suriajaya)
The conference "Value Distribution of Zeta and Lfunctions and Related Topics" has successfully ended on March 27, 2019. The whole conference program started with a colloquium, ZetaValue2019iTHEMS Special Mathematics Colloquium, on March 21, followed by the main conference held from March 22 to 26, and concluded with a one day workshop on March 27. We had more than 120 participants in total, among we had over 100 number theorists and overall about 111 mathematicians. We managed to gather people from over 20 different countries, and more precisely there were 50 participants coming from overseas from 40 different institutions. Number theorists from over 30 different institutions in Japan also took part in the conference. As far as we, the organizers, know, this is very rare achievement for a math conference in Japan; at least in analytic number theory field, this was the first ever conference in Japan to gather this many people coming from various places. We had 2 invited colloquium talks, 14 invited plenary talks, 9 contributed short talks, 15 contributed poster talks (excluding mine), and 9 contributed workshop talks. I would like to thank iTHEMS members and a few other RIKEN scientists who attended the colloquium. I hope that the talks were interesting enough and I really hope to maintain this communication and even boost our interdisciplinary connection further. Finally, the most important thing I would like to address here is: I deeply thank iTHEMS, and further, RIKEN who supported and assisted this conference, who made all of this possible. Thank you very much!! To all the assistants who helped me a lot from the preparation until the concluding process, please accept my sincere gratitude.

20190301
Seminar ReportReport of iTHEMS colloquium  Tropical Rain Forest
iTHEMS Colloquium was held on February 21st, inviting Dr. Akiko Satake, Professor of Kyushu University. Her lecture was entitled “Tropical Rain Forest.” In forests, flowering and fruit production are synchronized between different trees with irregular intervals of several years. Dr. Satake integrated longterm data and mathematical modeling, and found the triggers for mass flowering are temperature and drought. In fact, by using her model and the data of temperature and precipitation, she accurately predicted the mass flowering timing. This study will reveal the link between macroscopic (ecosystem) and microscopic (gene regulatory system) phenomena. Because the research topic is interesting and her presentation was easy for nonspecialist to understand, we enjoyed active discussion.

20181127
Seminar ReportiTHEMS Public Lectures at RIKEN Kobe Campus Open House
On Nov. 28, 2018, the annual open campus of RIKEN Kobe was held. From this year, iTHEMS, which has a Kobe office (SUURICOOL Kobe), joins this event and organized public lectures "Hot topics in Mathematical Sciences". This year 's program was Tetsuo Hatsuda "The world that mathematical sciences open" Ade Irma Suriajaya "How can something infinite become finite?" Jeffrey Fawcett "What are genomes?  Toward decoding the language of life  " Masato Taki and Noriaki Ogawa "Artificial intelligence and its medical application" Shigenori Otsuka and Shunji Kotsuki "Frontiers in weather forecast research" The lectures were held in the auditorium at the 8th floor of the Kobe IIB building (iTHEMS office is in the 7th floor). Each speaker gave a 3040 min. talk followed by lots of interesting questions from the audience. It was amazing to see that iTHEMS researchers are not only extraordinary in their own research but also super science communicators !

20181004
Seminar ReportiTHEMS colloquium held on October 3rd
Prof. Hideaki Aoyama from Kyoto University was the lecturer of the latest iTHEMS colloquium held on October 3rd. Prof. Aoyama has just joined iTHEMS as a senior visiting researcher. Welcome to iTHEMS, Prof. Aoyama! The colloquium was entitled "Economic Networks: a Physicist's View. " In the opening of the talk, Prof. Aoyama shared his personal recollection of Richard Feynman, one of the greatest physicists of the last century, and quoted his words. He went on to explain the techniques developed to explore the correlations and hidden relations buried in the huge amount of complex data which concern the economic activities of the real world. He pointed out that a certain kind of similarities can be observed between physics and economics, for example, the time correlation of the aftershocks of earthquakes and the bankruptcies occurred after calamities. The colloquium attracted a wide range of audience including those from outside RIKEN.

20180723
Seminar ReportiTHEMSCEMS Joint Colloquium was held on July 19
iTHEMSCEMS Joint Colloquium was held on July 19 at Okochi hall with a distinguished speaker, Prof. A. J. Leggett (Univ. Illinois at UrbanaChampaign). The hall was packed with full of audience (more than 150 participants) to listen the talk by the world's leading theorist in quantum physics. Prof. Leggett started his lecture with elementary considerations on classical radiation. Then he moves on to describe two photons emitted backtoback in atomic transition and subsequent observation of the photon polarizations. In the "objective local theory" in which (i) local causality, (ii) induction and (iii) microscopic realism are assumed, one can prove an inequality for certain correlation measurement (Bell's theorem). Since quantum mechanics violates the inequality, the natural consequence is that (iii) is not satisfied in quantum mechanics. The key idea behind is the "entanglement" in which information is stored in nonlocal manner in quantum mechanics. Then, he talked about the notions of quantum teleportation, quantum cryptography and quantum computer where entanglement plays the essential role. The audience listened his lecture attentively and was fascinated by the interesting aspect of quantum mechanics and its applications.

20180717
Seminar ReportSeries of lectures at Komaba Campus, Univ. of Tokyo
Series of lectures "Frontiers of Mathematical Sciences: Universe, Matter, Life and Information" were at Komaba Campus, Univ. of Tokyo, on every Wed. AprilJuly, 2018, for the 1st and 2nd year undergraduate students in Univ. Tokyo. Six researchers from RIKEN iTHEMS (Y. Inoue, Y. Yokokura, M. Tachikawa, J. Fawcett, T. Doi and M. Taki) gave 14 lectures altogether. The photo is the very last slide of M. Taki and himself (left) who gave the last lecture on July 11, as well as T. Tsuboi who organized this class. Undergraduate students seem to enjoy these lectures which cover the wide range of topics selected from the point of view of mathematical sciences. We plan to publish these lectures as a book in the near future.

20180702
Seminar ReportJoint innovation seminar between RIKEN iTHEMS and Denso IT lab. was held on June 28
On June 28, joint innovation seminar between RIKEN iTHEMS and Denso IT lab. was held. After the general introduction to the Denso IT lab. There were two talks from Denso IT lab. (Humancar interface; Machine leaning and computer vision) and two talks from RIKEN iTHEMS (Topology in classical systems; Hadrons in quantum chromodynamics). It turned out that the background of all 4 speakers are theoretical physics. The iTHEMS coffee room was filled with people from both labs. and lively discussions among participants continued until 8pm. This meeting would be a model case where "real" interactions between researchers in academia and industry are made possible.

20180629
Seminar ReportProf. Satoshi Aoki's one day lecture was held on June 26
On June 26, Professor Satoshi Aoki (Kobe Univ.) gave a series of lectures about "computational algebraic statistics and its applications". His lecture is about application of the Grobner basis to statistic theory. Lecture 1 was an introduction to ideal of polynomial rings and its relation to the Grobner basis. In Lecture 2, he explained Grobner basis in design of experiments. In Lecture 3, he explained Grobner basis in statistical hypothesis with contingency tables. There were more than 30 participants from inside and outside of RIKEN. Background of the participants are mathematics, statistics, physics, biology, information science and medical science. There were many questions from the participants on the mathematical and practical aspects of the Grobner basis, and the lively discussions continued at the time of lunch and coffee break. This lecture turns out to be a model case of having both mathematicians and practitioners together to discuss the power of mathematics and it applications.

20180611
Seminar ReportiTHEMS Colloquium was held on June 7
Prof. Yasumasa Nishiura gave a lecture at iTHEMS Colloquium which was taken place June 7th. His lecture was entitled "On the interplay between intrinsic and extrinsic instabilities of spatially localized patterns" and various patterns emerge from rather simple sets of differential equations were introduced. According to the lecture, spatially localized dissipative structures are observed in various fields, such as neural signaling, chemical reactions, discharge patterns, granular materials, vegetated landscapes, binary convection and block copolymer nanoparticles. Now, while these patterns are much simpler than single living cells, yet they seem to inherit several characteristic "living state" features, such as generation of new patterns, selfreplication, switching to new dynamics via collisions and adaptive morphological changes to environments. Prof. Nishiura explained that these behaviors stem from an interplay between the intrinsic instability of each localized pattern and the strength of external signals. The global geometric interrelation amongst all relevant solution branches of a corresponding system with approximate unfolding parameters was explored. He argued that a global geometric structure formed by all relevant solution branches gives us much more insight rather than conventional PDE approaches. The theme of the lecture was most pertinent to iTHEMS colloquium and the audience was fascinated by the power of the mathematical insight applied to varied subjects and phenomena.

20180521
Seminar ReportCatherine Beauchemin gave a short talk at Nerd Nite Tokyo on May 11
On Friday, May 11, Catherine Beauchemin gave a short talk at Nerd Nite Tokyo. She told the public that health science has serious issues with reproducibility of experiment results, and that the research culture incentivizes positive results rather than sound experiments. This is why you get reports in successive months about how eggs are unhealthy, then healthy. Or how a medical practice used for 20 years to reduce postsurgery infections actually makes them more likely. According to Catherine, if doctors and health scientists want to be trusted more, they need to better communicate the uncertainty of results, do fewer (but larger) experiments to produce more robust results, and accept that negative results are just as worthy of publication as positive results. She also talked about how health science has math problems. Too many people in that field don't understand math/statistics well, and blindly trust equations even when those equations are misapplied and give incorrect results. There is a big opportunity for scientists with a background in math to work with health scientists and improve the quality of research in a field that is important for everyone. She is already starting a project along these lines  please join her to promote the goals of iTHEMS and health sciences! And if you want to speak at a future Nerd Nite about your own research, please contact Don Warren (donald.warren@riken.jp) for information.

20180507
Seminar ReportiTHEMS Colloquium was held on April 23
iTHEMS Colloquium was held on April 23rd, inviting Dr. Kazuhiro Sakurada, Deputy Program Director of RIKEN Medical Sciences Innovation Hub Program, also at Sony CSL, and Dr. Jun Seita, Unit Leader of AI based Healthcare and Medical Data Analysis Standardization Unit, RIKEN Medical Sciences Innovation Hub Program as the lecturers. Dr. Sakurada gave the lecture first, entitled "The Description of biological phenomena as open system." There, he explained his approach to describe the lifecourse changes of individual people by applying the discretization model and Markov chain model. Then followed Dr. Seita’s lecture, which is entitled "Every Biological Variable has a Different Dynamicrange." He introduced an open platform for objective gene expression profiling named Gene Expression Commons. Their lectures exhibited the power of the interdisciplinary research in the most perspicuous way.
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