Person of the Week
103 news

20231116
Person of the WeekSelfintroduction: Dongwook Ghim
I am a theoretical physicist working on highenergy physics, HEPTH. More precisely, I am interested in the spectral problems of strongly coupled gauge theory. The infamous quark confinement of Quantum Chromodynamics and the mass gap generation of YangMills theory are the most wellknown spectral problems involving strongly coupled gauge theory. I mainly use two orthogonal toolkits to tackle such problems; supersymmetry and quantum simulation. I have worked on the computation of the twisted partition function of supersymmetric gauge theories, which appear in the string theory context, showing a strong relation with the geometry of CalabiYau manifolds. Simultaneously, I am eager to develop a quantum algorithm that can capture the spectra of gauge theories, without the aid of supersymmetry. The latter targets lowdimensional lattice gauge theory in practice. But I dream of capturing the physics of three or fourdimensional gauge theory on the quantum processor near future. I look forward to a fruitful collaboration with people in iTHEMS, RIKEN.

20231006
Person of the WeekSelfintroduction: Yuto Yamamoto
I specialize in tropical geometry, a field of mathematics that naturally emerges when considering the limits of spaces with respect to some parameters. My primary research interest lies in calculating the limits of invariants of the spaces using tropical geometry. Despite being a relatively new field, tropical geometry has already demonstrated its applicability to other various sciences. During my time at iTHEMS, I look forward to exploring such applicational aspects of tropical geometry as well.

20231006
Person of the WeekSelfintroduction: Misako Tatsuuma
I'm Misako Tatsuuma, and I joined iTHEMS as a Research Scientist in October 2023. My research focuses on planetary formation theory. Specifically, I'm working on the formation process of planetesimals, which are kilometersized bodies like comets and asteroids, from micronsized cosmic dust grains. This process is still not fully understood and has been extensively studied through observations, explorations, experiments, and simulations. My approach involves investigating the material strengths of dust aggregates using dust grain Nbody simulations and comparing the results with explorational findings of comets and asteroids in our solar system. I got my Ph.D. in March 2022 at the University of Tokyo and subsequently began the JSPS fellow (PD) at Tokyo Institute of Technology. As for personal, I'm a mother of two and facing the ongoing challenge of balancing childcare and research.

20231005
Person of the WeekSelfintroduction: Shinichiro Fujii
My name is Shinichiro Fujii. I was originally a nuclear theorist. After finishing my PhD at Kyushu University in 2000, I joined RIKEN as a special postdoctral researcher. After that, I had several positions including associate professor at the University of Tokyo. After a period of unemployment at the age of 40 due to the term limit, I was hired by JSTCRDS as a fellow in 2013. I conducted research and survey activities to formulate Japan's science and technology policy for 5 years. After that, I was involved in the management of large national projects related to quantum computers and quantum communications, such as JSTERATO, QLEAP and Moonshot Goal 6, at the University of Tokyo and Yokohama National University for 5 years. 23 years after beginning my career as a researcher at RIKEN, I am back to RIKEN as a coordinator in 2023. I would like to contribute to creating a better environment for researchers and enhancing the value of RIKEN.

20230802
Person of the WeekSelfintroduction: Yuta Sekino (2023)
I am Yuta Sekino. After finishing my Ph. D at Tokyo Institute of Technology in 2019, I worked in RIKEN as a JSPS Postdoctoral Fellow (201921) and Postdoctoral Researcher in ABBL (202123). During 20212023, I also belonged to iTHEMS as a concurrent member. In July 2023, I officially joined iTHEMS as a Postdoctoral Researcher associated with RIKEN Quantum. I am a theoretical condensedmatter physicist mainly working on ultracold atomic systems. My main research interest is superfluidity, superconductivity, and spin transport. Because these phenomena have been widely discussed not only in condensedmatter physics but also in nuclear physics and astrophysics, I would like to collaborate with iTHEMS researchers working in these fields. As a member of RIKEN Quantum, I also would like to apply quantum computational methods to nonequilibrium phenomena such as postquench dynamics in quantum spin systems. Because quantum computing would have the potential to tackle unsolved problems in every field of science, I would be happy to have interdisciplinary discussions in RIKEN Quantum. At iTHEMS, I hope to broaden my research horizon through discussions with researchers in various fields.

20230802
Person of the WeekSelfintroduction: Steffen Backes
Hello! My name is Steffen Backes, and I just joined RIKEN Quantum as a Senior Scientific Researcher. My research interest is focused on the physics and phenomena that can be found in strongly correlated electron systems, such as transition metal oxides, cuprate and ironbased superconductors, nickelate materials, or other lowdimensional lattice systems. In these systems the Coulomb repulsion between electrons gives rise to unexpected emergent phenomena such as magnetism, charge order, superconductivity, the metaltoinsulator transition, changes in their optical properties, and many more. My particular interest lies in going beyond an effective singleparticle description of the electronic system, using perturbative and nonperturbative methods. For this, I am employing the GW approximation, Dynamical meanfield theory and its extensions such as cluster methods, or combinations in the form of GW+DMFT. In iTHEMS I will investigating how current Quantum processors, or "Noisy Intermediate Scale Quantum" (NISQ) devices can be used to solve the problems we encounter when studying such correlated electron systems with stateoftheart numerical methods. Since these devices are inherently noisy, the development of faulttolerant algorithms is one of my major goals.

20230802
Person of the WeekSelfintroduction: Yaokun Lei
My name is YaoKun Lei, and I joined iTHEMS in August 2023. I am originally from a city in the south of China. After finishing my undergraduate studies, I pursued a Ph.D. at Peking University, where I focused on studying the significant role of dynamic solvent effects in chemical reactions in condensed phases using enhanced sampling methods. Upon completing my Ph.D., I became a visiting scholar at the ShenZhen Bay Laboratory. During this period, I developed efficient strategies for rare event sampling and reaction coordinate analysis without prior knowledge of the reaction mechanism, using Reinforcement Learning and likelihood maximization techniques. In July 2021, I joined Theoretic Molecular Science Laboratory at RIKEN. Over the past two years, my research has been centered around developing accurate, efficient, and transferable machine learning force fields for systems embedded in external potentials, with the aim of accelerating QM/MM simulations using multiscale equivariant graph convolution networks. Looking ahead, I am enthusiastic about leveraging quantum computing to accelerate largescale molecular dynamics simulations. Specifically, I plan to utilize highprecision quantum computational results to expedite the parameterization of machine learning force fields. Additionally, I aim to enhance sampling in highdimensional spaces through quantum computing. During my time at iTHEMS, I hope to have the opportunity to collaborate with researchers from different disciplines and embark on exciting new explorations.

20230703
Person of the WeekSelfintroduction: Jan SchuetteEngel
Hi, I'm Jan SchütteEngel and I recently started as a RIKENBerkeley fellow. My research focusses on gravitational waves (GWs) from the early and late universe. In particular, I'm interested in cosmological and astrophysical GW sources and what we can learn from the emitted GW signals about new physics phenomena. We expect many GW signals which encode new physics phenomena over a broad frequency range. Therefore, I also investigate novel detection ideas for GWs in frequency regimes that are difficult to probe with laser interferometers. Finally, I am working on novel ideas for axion dark matter direct detection. This line of research is highly interdisciplinary and often uses techniques from condensed matter physics and quantum sensing.

20230606
Person of the WeekSelfintroduction: Derek Beattie Inman
Hello! My name is Derek Inman, and I am a scientist at iTHEMS whose research is focused on cosmology. Our Universe contains a substantial amount of dark matter the behavior of which we broadly know, but the composition of which we don’t. I try to understand how different ideas for what dark matter is (particles? black holes? something else?) change how the Universe looks and evolves at various times and length scales. I am particularly interested in cosmological structure formation, which rapidly becomes a nonlinear problem and so I tend to use numerical simulations run on supercomputers to understand the relevant physics.

20230511
Person of the WeekSelfintroduction: Kohei Hayashi
Hi, my name is Kohei Hayashi. I am a visiting researcher as the postdoctral fellowship of Japan Society for the Promotion of Science (JSPS). So far, I have been working on explaining macroscopic behavior of some physical quantities from microscopic models. Especially, my interest lies in universality that arises in fluctuations of Markov processes. An important example of such universality class is the KardarParisiZhang universality class and it has been observed in various probabilistic models. I am trying to understand mechanisms or backgrounds of such universality in mathematically rigorous ways.

20230428
Person of the WeekSelfintroduction: Rongyang Sun
My name is Rongyang Sun. I joined RIKEN in October 2021 as a Postdoctoral Researcher in RCCS and RQC. Now, I am very glad to hold this concurrent position in iTHEMS. As a fullstack researcher in computational quantum manybody physics, my ultimate goal is to understand the fantabulous nature of quantum manybody systems by taking advantage of modern supercomputing systems and quantum computers. Towards this goal, I am developing advanced tensor network algorithms, maintaining highperformance tensor computing software, and applying these tools to the study of strongly correlated systems like interacting electrons and frustrated spins. Meanwhile, I am also exploring the possibility of utilizing nearterm quantum computers to arrive at the same destination.

20230428
Person of the WeekSelfintroduction: Tomonori Shirakawa
My name is Tomonori Shirakawa. I joined iTHEMS as a Senior Research Scientist in April 2023. I am interested in quantum manybody phenomena in condensed matter physics. To better understand quantum manybody phenomena, I have been working with various numerical methods. In particular, I have recently been exploring more efficient ways to solve quantum manybody problems using quantumclassical hybrid algorithms, quantum algorithms, and tensor network methods.

20230410
Person of the WeekSelfintroduction: Seishiro Ono
My name is Seishiro Ono. I received my Ph.D. from the University of Tokyo in March 2023, and then I joined RIKEN iTHEMS in April 2023. My research interests lie in quantum condensed matter physics. I have been fascinated by the diversity of this field, and I am eager to understand the various phenomena from a unified point of view. I am currently investigating a unified understanding of superconductivity based on symmetry and topology. In addition, I have recently become interested in experimental signatures of topological nature, applications of machine learning to materials science, and quantum simulation of strongly correlated systems.

20230407
Person of the WeekSelfintroduction: Zixia Wei
My name is Zixia Wei, and I got my Ph.D. from Yukawa Institute, Kyoto University in March 2023. I work on many different aspects of the AdS/CFT correspondence. The AdS/CFT correspondence relates a gravitational theory to a nongravitational theory in a lowerdimensional system. Recently, I am interested in studying statistical physics with the help of the AdS/CFT correspondence. Thermal states in nongravitational systems, which are often the targets of statistical physics, are related to black holes via the AdS/CFT correspondence. Obvious observations in black holes are sometimes nontrivial when translated back to statistical systems. I am working on making nontrivial conjectures in general statistical systems by considering black holes and then trying to prove them back in statistical systems.

20230406
Person of the WeekSelfintroduction: CheYu Chen
Hi, my name is CheYu Chen, a Taiwanese researcher, joining RIKEN iTHEMS as an SPDR in April 2023. I got my Ph.D. in Physics from National Taiwan University in 2019. After my graduation, I stayed as a postdoc at LeCosPANTU (20192020) and then became an AS postdoc at the Institute of Physics, Academia Sinica (20202023), before coming to RIKEN. My interest is mainly in gravitational physics, including modified gravity and the phenomenological aspects of quantum gravity. In particular, I'm currently working on using stateoftheart black hole observations to test general relativity (GR), or even to probe putative nonGR physics. The direct detection of gravitational waves emitted from binary black hole mergers, and the images of supermassive black holes, have ushered in a completely new era in which directly probing spacetimes near black holes becomes possible. There are several interesting nonGR physics, some of which could even be motivated by quantum gravitational effects. These nonGR physics could induce nontrivial or even unique imprints on gravitational waveforms and black hole images, and hence can possibly be tested in the future. A better understanding of this topic can tell us how well GR describes such extreme spacetime regimes, and if it were to be modified, which direction is more observationally preferred. I'm looking forward to the fruitful discussions with the iTHEMS members in the future.

20230405
Person of the WeekSelfintroduction: Tomoya Nagai
My name is Tomoya Nagai. I joined as a coordinator in April 2023. I started working after getting the Ph.D. in astrophysics and have worked in science communication, R&D strategy development, research funding and R&D management. Until March 2023, I worked at KEK and Kobe University, where I was manager of research projects using the supercomputers “Fugaku". I will do my best to help you in your research.

20230405
Person of the WeekSelfintroduction: Tingyu Zhang
My name is Tingyu Zhang, and I joined iTHEMS as a junior research associate in April 2023. Now I am involved in a PhD program in physics at the University of Tokyo. I mainly focus on the study of quantum manybody systems and nonequilibrium physics. Specifically I’m now studying the transport phenomena in cold atomic systems, through Green’s function methods and the perturbation theory. I’m looking forward to discussing physics with other researchers in the future.

20230207
Person of the WeekSelfintroduction: Christian Quirouette
Hi, my name is Christian Quirouette. I am a postdoctoral fellow at Toronto Metropolitan University in Canada. My field of research is virophyiscs, i.e. applying methods of physics to problems in virology. My research primarily focuses on stochastic mathematical modelling of viral infections. I’m excited to be working here at iTHEMS and have the chance to discuss and possibly collaborate with other researchers in other fields.

20230203
Person of the WeekSelfintroduction: Liang Zhang
I’m a Ph.D. student form Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences (CAS). And I came to iTHEMS on January 26th, 2023. When I was a undergraduate learning nuclear physics, I’m curious about how we can calculate the interactions between nucleons. I think it is the key for us to understand nucleus better. Beside this, I also learnt that there are hypernucleuses, where several nucleons are replaced by other baryons. So, if the interactions can be calculated from quark model and QCD theory, it allows us to study not only the normal nucleuses but also hypernucleuses which may exist at the beginning of the universe. HAL QCD is a great way to study the interactions between baryons by using lattice QCD calculation. I’m so glad to have this chance to study HAL QCD in iTHEMS. I hope I can receive knowledge and friendship here.

20221102
Person of the WeekSelfintroduction: Puttarak Jaiakson
My name is Puttarak Jaiakson. I hail from Thailand and I obtained my bachelor’s degree there. I then moved to Canada to join the PSI program and completed my PhD at Perimeter Institute. I joined iTHEMS in November 2022 as a postdoctoral researcher and I have been very excited to learn, share, and cultivate new ideas with fellow researchers in this interdisciplinary environment. My research mainly focuses on theoretical aspects of gravity, leaning especially towards the theme of black holes, holography, and quantum gravity. I am interested in the idea of quasilocal holography, centering around the study of gravity in finite regions of spacetime where a wealth of fascinating mathematical structures and physics is unfolded. One topic which I have been currently pursued is the underlying correspondence between gravitational physics near finite null boundaries (such as black hole horizons) and Carrollian hydrodynamics, an unusual type of fluid dynamics living at the opposite corner to the conventional NavierStokes fluid dynamics. This correspondence will certainly shed light on the better understanding of black holes and their thermodynamical properties. I also believe that the connection between gravity and hydrodynamics will open a new route for the grand quest to quantize gravity.

20221102
Person of the WeekSelfintroduction: Maria Manuela Saez
Hola!, This is Maria Manuela Saez, an Argentinian astronomer and a new RIKEN  Berkeley postdoctoral fellow. I'm interested in astrophysics, and in particular, my research focuses on the study of corecollapse supernovae and the role that neutrinos play in these astrophysical environments. Corecollapse supernovae are the final evolutionary stage of massive stars and represent a longawaited observation target for neutrino telescopes. To explain these events, one needs an interdisciplinary field of research that combines nuclear physics, particle physics, astrophysics and numerical simulations. Studying the signals that the supernovae' neutrino fluxes leave in the detectors, with an appropriate neutrino flavor discrimination, is possible to infer properties of the physics of the neutrinos involved and to study scenarios with nonstandard neutrino properties. The structure of the neutrino mass spectrum and lepton mixing is imprinted into the detected signal. My goal is to contribute, from a theoretical perspective to the definition of strategies for detecting and studying neutrinos in large underground neutrino and dark matter detectors. I'm looking forward to discussing and collaborating with iTHEMS people.

20221102
Person of the WeekSelfintroduction: Ermal Rrapaj
Hi, my name is Ermal Rrapaj, and I am a new RIKENBerkeley fellow. My research centers on the intersection of quantum many body physics and astrophysics. The general focus is on how particle interactions affect the properties of extreme environments such as supernovae and neutron stars and how they relate to earth experiments. The main research topics include properties of nuclei that could be tested in future experiments, neutrino nucleon matter interactions, transport properties of neutron stars, supernovae equation of state, and astrophysical implications from BSM particles. In recent years Ermal has been exploring how new technologies such as machine learning (neural networks) and quantum computing can aid in these research venues.

20221101
Person of the WeekSelfintroduction: Thomas Hitchcock
Hi, I’m Thomas Hitchcock. I grew up in the UK, studying Genetics and Systems Biology at the University of Cambridge, before moving up to the University of St Andrews to do my PhD in Evolutionary Genetics, and have now joined iTHEMS as an SPDR. I’m interested in why organisms appear the way they do, and how we can use evolutionary theory to better understand this. In practice, I’ve study two main flavours of problem, (1) when and why do organisms (and genes) come into conflict with one another, and (2) how are organisms (and genes) expected to weight different fitness tradeoffs. To tackle these problems, I use a mix of population genetics and evolutionary game theory, and focus mainly on unusual genetic systems, life histories, and ecologies, which I hope might prove particularly clear tests of theory. I’m excited to discuss and learn from the wide variety of researchers at iTHEMS, and hopefully incorporate some new mathematical tools and frameworks into ecology and evolution.

20220704
Person of the WeekSelfintroduction: Christy Kelly
Hi, I'm Christy Kelly. I studied physics for my undergraduate degree in London before moving to Edinburgh to do a PhD in theoretical physics at HeriotWatt university, completed in early 2022. I have now joined iTHEMS as an SPDR. I am interested in gravity, especially coarse aspects of gravity that persist in the absence of differentiable structure; in more physical terms, we can perhaps think of this as gravity in regimes where quantum fluctuations become significant. In such regimes, basic mathematical tools such as calculus are no longer valid and it becomes nontrivial how to characterise even such fundamental notions as curvature. To get around this problem, I hope to exploit the recently flourishing mathematical field of optimal transport theory, which has already become a paradigm for the study of low regularity Riemannian geometry and has seen some very exciting recent developments in the Lorentzian case. Unexpected connections to different fields of physics also arise naturally in the optimal transport theoretic framework: for instance, the Einstein equations can be characterised in terms of the convexity/concavity properties of certain entropy functionals along choice trajectories in spacetime. Optimal transport theory also provides a notion of curvature for networks which has proved of some structural significance; I hope to also take this line of research forward during my time here at iTHEMS.

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

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

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

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

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

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

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

20220406
Person of the WeekSelfintroduction: Tomoya Naito
My name is Tomoya Naito. I joined RIKEN iTHEMS as an SPDR in April 2022, while I have participated in many activities in iTHEMS including the iTHEMSphys study group and the iTHEMS mathphys working group so, probably, some of you have known me. My research topics are related to computational quantum manybody problems, especially density functional theory (DFT). In principle, one can obtain all the properties of quantum manybody problems by solving the manybody Schrödinger or Dirac equation; however, it is, in practice, difficult to solve it. DFT, developed by Hohenberg, Kohn, and Sham, is one of the efficient methods to solve such problems. DFT has been applied to the study of atomic nuclei, atoms, molecules, and solids for decades, while there are still many fundamental things to be solved or understood. My research topics are briefly divided into two parts: fundamental studies of the DFT and studies of quantum manybody problems (atomic nuclei, atoms, molecules, and solids) using DFT. Recently, I have started an astrophysical study using knowledge of nuclear physics and a study of the mathematical aspect of DFT in collaboration with iTHEMS (previous or current) members. I look forward to extending collaborations with iTHEMS colleagues!

20220406
Person of the WeekSelfintroduction: Jizhou Li
My name is Jizhou (GJoe) Li. Born and raised in Beijing, got my PhD from the Washington State University, I’m now thrilled to join the RIKEN iTHEMS team as a postdoc researcher. A theoretical physicist by training, I have worked on nonlinear dynamical systems and quantum chaos during my PhD and postdoc years. After joining the RIKEN in April 2022, I will embark on a new journey in the field of computational virophysics to study the dissemination of viruses in various circumstances, as well as the interactions between the viruses and the hosts environments. Looking forward to expand my spectrum and learn from collaborators in different fields.

20220406
Person of the WeekSelfintroduction: Keiichi Morita
My name is Keiichi Morita, and I joined iTHEMS in April 2022 as a junior research associate / student trainee. I am now involved in a Ph.D. program at the SOKENDAI University. The main question of my research is how adaptive evolution can determine species coexistence and structures of ecological communities. I focus on rapid adaptation which can change the strength and directions of species interactions and finally affect population dynamics. I hope to understand how the evolution of an individual phenotype can affect species coexistence by formulating transient processes and finding conditions of coexistence from analysing and simulating my mathematical models. I consider analyzing experimental data and demonstrating my mathematical models. My final goal is to discover a general rule in ecology. I am looking forward to interacting with other members working with various interests in iTHEMS and finding a new direction of research out of it.

20220401
Person of the WeekSelfintroduction: Yan Lyu
I am a Ph. D candidate in Peking University, China, and I joined iTHEMS on April 1st 2022 as a student trainee. I am interested in understanding the interactions between hadrons from the fundamental theory, i.e., quantum chromodynamics (QCD). It is in some sense similar with determining the Coulomb interaction between two objects by calculating a simple integral using a pen and a piece of paper, like highschool students usually do in their physical class. However, as far as QCD is concerned, such an integral is too complicated to be done by using a pen and a piece of paper, thus I employ the socalled lattice QCD method to calculate such an integral by supercomputers. Once the interactions are determined from QCD, one can use them to various systems from nuclei to neutron star. I am very happy to join iTHEMS, and I look forward to interacting with people from various fields.

20220401
Person of the WeekSelfintroduction: Kotaro Murakami
My name is Kotaro Murakami and have joined iTHEMS since April 2022 as a student trainee. My research is to solve the mystery of hadrons from the firstprinciple calculation of quantum chromodynamics (QCD). QCD is a theory describing the dynamics of quarks and gluons, and hadrons are composed of these particles. There are several hadrons we do not know how are created from quarks and gluons, which are called exotic hadrons. My ultimate goal is to identify all of the hadrons including exotic hadrons from QCD. I am working on the lattice QCD studies of baryon resonances from mesonbaryon scatterings. I hope to have fruitful discussions in iTHEMS with not only people in particle physics or hadron physics but people in other fields.

20220401
Person of the WeekSelfintroduction: Xun Liu
My name is Xun Liu, and I joined iTHEMS in April 2022 as a student trainee. I am now involved in a PhD program at the University of Tokyo. My current research project and interest mainly lies in the field of twodimensional conformal field theory, string theory, and string field theory. I am also interested in the relationship of these fields with formal mathematical topics, including group and representation theory, and analytical geometry. I am looking forward to interacting with mathematicians to form a more mathematical welldeveloped language in describing CFT and string theory.

20220302
Person of the WeekSelfintroduction: Masato Itami
My name is Masato Itami, and I have joined iTHEMS as a visiting scientist in March 2022. I love stochastic things by nature, so I am currently studying the universal form of stochastic equations of motion for fluctuating objects in nonequilibrium systems. I am looking forward to interacting with people from various fields. By the way, my hobby is chess, so if you like chess, let's play chess together while/without talking about science.

20211129
Person of the WeekSelfintroduction: Tomoki Nosaka
My name is Tomoki Nosaka. I have joined RIKEN iTHEMS as a research parttime worker in November 2021. My research field is the theoretical physics. I have been trying to reveal new aspects of Mtheory, which is supposed to be the theory of everything though still being mysterious, by means of the supersymmetric gauge theories, matrix models and their integrability. Recently I am also interested in the quantum information theory and the various notions of chaos in quantum manybody systems which are found to be closely related to the black hole physics. I am looking forward to interacting with people in iTHEMS working with various research interests and finding a new direction of research out of it.

20211013
Person of the WeekSelfintroduction: Gilberto Nakamura
My name is Gilberto Nakamura and I joined iTHEMS as a postdoctoral researcher in Oct 2021, after working as a postdoctoral fellow at IJCLab/CNRS in France. I'm interested on the role of noise and correlations in biologically inspired systems. The relation between fluctuations and correlations lies at the heart of the theory of critical phenomena, with ramifications in Statistical Physics and Quantum Field Theory. Fluctuations in biological systems are further exacerbated by the innate variability of organisms, adding richness to the dynamics and promoting the emergence of complex behavior. More recently, I have worked on diseasespreading dynamics, viral infections, and migration of cancer cells, all of which have a significant impact on human health and require continued interdisciplinary efforts across Mathematics, Physics, and Biology. My current focus has been on bottomup approaches, starting from microscopic stochastic models and working them out into the hydrodynamic limit, with support from numerical Monte Carlo simulations, followed by parameter extraction from data. I am sure the interdisciplinary environment fostered by iTHEMS will promote new collaborations and further advance my research goals.

20211004
Person of the WeekSelfintroduction: Yixin Guo
My name is Yixin GUO, a Junior Research Associate joined in iTHEMS from October 2021. I come from China, and now study in the Doctoral Course at The University of Tokyo. I am majoring in theoretical nuclear physics. I am mainly interested in (but not only) the quantum manybody problem, nuclear structure theory, density functional theory, and nuclear reaction theory. I also have some experience in the accelerator physics. I look forward to exchanging ideas with various researchers from different fields.

20210908
Person of the WeekSelfintroduction: Matthias Berwein
My name is Matthias Berwein and I'm from Germany. I did my undergraduate studies in physics at TU Munich from 2006 to 2011, followed by a PhD 20122016 also at TU Munich in the group of Nora Brambilla. Then I came to Japan for my first postdoc at Tohoku University in Sendai under a JSPS fellowship with Yukinari Sumino. Since 2018 I've been at RIKEN, first in the SPDR program at Quantum Hadron Physics Lab, and from 2021 in iTHEMS. The focus of my research lies in theoretical studies of the strong interactions through the theory of quantum chromodynamics and with a special emphasis on heavy quarks. I have worked on several projects on the static quark potential, heavy quarkonium hybrids, and heavy quarks at finite temperature, using perturbative calculations and effective theory methods. Currently, I'm studying properties of the energymomentum tensor in these environments. I look forward to many fruitful interactions with fellow researchers here at iTHEMS.

20210805
Person of the WeekSelfintroduction: Congcong Le
My name is Congcong Le from China, and I join iTHEMS on August 1st 2021 as a Postdoctoral Researcher. After graduation, I came to the Institute of Physics, Chinese Academy of Sciences to study theoretical physics, and obtained my PhD in July 2017. My research focuses on the theoretical study in condensed matter systems, including unconventional superconductivity, strongly correlated system, and novel topological system (topological insulators, Dirac semimetal, Weyl semimetal), and I start to be interested in twisted bilayers and topological phases in the nonHermitian systems. I have enjoyed using mathematics to explore condensed matter physics and working with theorists and experimenters. In my spare time, I like Chinese chess, badminton, table tennis and climbing.

20210720
Person of the WeekSelfintroduction: Yalong Cao
I am a mathematician doing research on algebraic geometry, differential geometry and mathematical physics. I am particularly interested in understanding YangMills theory on CalabiYau 4folds and how it is interacted with enumerative geometry. I am eager to understand how such theory could lead to unexpected relations with other areas. It is my great pleasure to join RIKEN iTHEMS and I am looking forward to having exciting discussions with you.

20210702
Person of the WeekSelfintroduction: Etsuko Itou
I'm Etsuko Itou, a Postdoctoral Researcher (Concurrent) since July 2021. I'm interested in quantum field theories, in particular, quantum chromodynamics (QCD) in extreme regimes. Although QCD in the superfluid phase, which occurs in lowtemperature and highdensity regimes, is still an unsolved area due to the infamous sign problem, a theoretical understanding is urgently needed in relation to neutron star physics. I am working on various numerical approaches to understanding quantum field theories with the sign problem. For example, I utilize the conventional classical supercomputers to study qualitative properties of modified QCD without the sign problem, and I develop quantum computation algorithms based on a new formula where the sign problem does not emerge.

20210611
Person of the WeekSelfintroduction: Yantao Wu
My name is Yantao Wu. I joined iTHEMS in June 2021. My research field is in computational and theoretical statistical physics. I'm also interested in quantum computing. I obtained my PhD in physics from Princeton University in May 2021. During graduate school, I have worked on renormalization group of quantum and classical statistical systems in the context of Monte Carlo simulations. I'm also quite familiar with pathintegral molecular dynamics. Currently, I'm interested in developing tensor network algorithms for quantum dynamics in one dimension and ground state calculations in two dimensions. In particular, I'm interested in the approximate canonical form of 2D tensor networks, and its associated entanglement structure. I'm also interested in issues related to quantum dynamics, such as entanglement evolution and eigenstate thermalization hypothesis at the edge of the energy spectrum. I'm based in UC Berkeley, and would be glad to host any iTHEMS visitors in the bay area. Based in UC Berkeley, I have recently got interested in the hardware of quantum computing as well. I hope that we can one day see the ENIAC of our generation. In my spare time, I like soccer, climbing, poetry, and Go (not very good though).

20210528
Person of the WeekSelfintroduction: Ryo Namba
Pursuit of the fundamental law that governs the evolution of our universe, is the end goal of cosmology. Our universe is known to be expanding. It is not only expanding, but has been, and perhaps will be, expanding. The driving force of the current accelerated expansion, often called dark energy, is still beyond our understanding, despite that the fate of the universe entirely depends on the nature of dark energy. Furthermore, cosmological observations provide indications that an accelerated expansion also took place at the earliest stage of our universe, known as inflation, and that the seeds of all the structures we observe today were encoded during this period. Thus the physics in the inflationary era is of essential importance, fixing the initial conditions of our universe. The forthcoming advancement of multimessenger (photons, neutrinos, and gravitational wave), multifrequency observations opens up the possibility of probing such cosmological signals in novel manners. My research focus is encapsulated in the studies of interactions at cosmological scales, ranging from the highestenergy processes at the onset of the universe to the laws of gravity at the largest distances, by making use of the knowledge of quantum field theory, elementary particle physics and gravitational theory as technical tools. Interactions in cosmology are inevitably those in a gravitating system, and they reserve a large domain of unresolved mysteries that provide a fascinating ground to explore. Understanding the physics in both ends of these extremes is necessary to reveal the origin and fate of our universe. Many different branches of physics are involved in this research adventure, and extending the border of scientific disciplines is of essential importance. [Brief academic history] I received my Ph.D. from the University of Minnesota (USA), and continued my research activities as a postdoctoral researcher at Kavli IPMU (Japan), McGill University (Canada), and TsungDao Lee Institute (China), before joining RIKEN iTHEMS in May 2021. I have worked on research projects on particle production in the early universe, thermalization process (reheating), modified gravity theories (scalarvectortensor theories, massive/bimetric gravity), etc.

20210521
Person of the WeekSelfintroduction: Akira Harada
I'm Akira Harada, a RIKEN SPDR since April 2021. I'm interested in astrophysics, especially supernovae. The corecollapse supernova (CCSN) is the explosive death of a massive star. Because of the extreme environment realized at the center of the CCSN, the explosion mechanism involves a vast field of physics, namely hydrodynamics, nuclear physics, neutrino physics, and gravitational physics. Besides, understanding such a complicated phenomenon requires numerical simulations. I'm trying to reveal the mechanism by exploiting all these pieces of knowledge. I'd like to get stimulated from interdisciplinary conversations with iTHEMS people.

20210517
Person of the WeekSelfintroduction: Naritaka Oshita
I am a theoretical physicist who works on gravity, cosmology, and quantum field theory. Quantum fluctuations of mater/gravitational fields in an expanding universe or a black hole exhibit thermal radiation and superradiance. These phenomena are important to understand the thermal nature of the gravitational systems and how information of matter is encoded there. Also, the classical linear perturbations of a black hole are characterized by the quasinormal modes of the black hole. This is useful to test classical/quantum gravity theories by the observation of gravitational waves. Beyond the linear perturbation in gravitational systems, I am also working on nonperturbative phenomena of quantum fields such as vacuum decay in strong gravity. The standard model of particle physics predicts that the Higgs field is metastable, which means that our Universe might eventually undergo a catastrophic vacuum decay and be filled with negative vacuum energy. The vacuum decay process is therefore important to understand the history and fate of the Universe.

20210513
Person of the WeekSelfintroduction: Eiji Inoue
I'm Eiji INOUE, a new member of iTHEMS as a special postdoctoral researcher in mathematics. My current interest is Kahler geometry of algebraic variety. Algebraic variety is (locally) the solution set of polynomials, say x^2 + y^2 1 = 0. While its origins trace back to ancient Greek, it still fascinates many mathematicians: you can find many Fields medalists, including all Japanese medalists, are awarded for their monumental works on algebraic variety. CalabiYau variety is a special class of algebraic varieties attracting attention in string theory. A CalabiYau variety admits a KahlerEinstein metric, which can be thought of as a canonical 'shape' of the variety. Though a general variety in other classes does not necessarily admit such canonical metrics, it is gradually believed by not a few specialists that any variety has a unique degeneration to another variety admitting a canonical metric in some sense. My recent study gives a mathematical formulation of this problem. This framework has a special aspect: it naturally possesses a new parameter λ which plays a role analogous to the inverse temperature. When λ is sufficiently low, canonical metrics, which you may see as 'equilibrium states' of the variety, are unique if it exists. On the other hand, when λ is sufficiently high, canonical metrics are not unique and the absolutely stable states may break the symmetry of the variety. It is reminiscent of phase transition. I am looking forward to discussing this phenomenon with researchers in other areas.
103 news