News
118 news in 2019
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2019-03-20
Award
Dr. Hongo receives FY2018 Young Scientist Award of the Physical Society of Japan
Masaru Hongo (iTHEMS, SPDR) received "FY2018 Young Scientist Award of the Physical Society of Japan" on March 15, 2019 for his work, Relativistic hydrodynamics from quantum field theory in the local Gibbs ensemble published in Phys. Rev. D92, 065008 (2015). Congratulations !
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2019-03-18
Award
Dr. Chang receives 10th annual RIKEN Research Incentive Award
Jason Chang (iTHEMS Research Scientist) received "FY2018 Researcher Incentive Award" on March 12, 2019 for his recent paper; A per-cent-level determination of the nucleon axial coupling from quantum chromodynamics, published in Nature 558 (2018) 91-94. Congratulations !
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2019-03-14
Hot Topic
Summary of nuclear astrophysics workshop at Hokkaido University
Nuclear astrophysics workshop was held at Hokkaido University from 6th to 8th of March, 2019, under the support of iTHEMS as well as other institutions and centers. Major issues of this meeting are nuclear data and heavy-element synthesis. The meeting was very successful with around 60 researchers coming from various fields such as nuclear physics, particle physics, astronomy, astrophysics, astrochemistry, earth and planetary physics. Details of this workshop can be found at their offical web site.
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2019-03-12
Featured Paper of the Week
Diffusive Nambu-Goldstone modes in quantum time-crystals
Symmetry and its breaking is one of the most important notions in modern physics. It is known that when a continuum symmetry is spontaneously broken, there appears a gapless excitation called the Nambu–Goldstone (NG) mode. Such a mode appears in several length scales. In the femtometer scale, pions that are responsible for nuclear force, are the NG modes associated with chiral symmetry breaking. In the meter scale, the sound mode in solid is the NG mode associated with spontaneous breaking of translational symmetry. In this paper, we study the NG modes associated with spontaneous breaking of the continuous time-translation symmetry in an open quantum system. For this purpose, we study a system with a van der Pol type nonlinear-friction. By considering small fluctuations around a time-periodic mean-field solution, we find that a gapless collective mode, which is a diffusive one, necessarily appears; this is nothing but the NG mode of a time crystal. We also show that noncommutative breaking of the time-translation and U(1) symmetries results in mixing of the NG modes, and the (typically) propagating NG mode appears.
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2019-03-12
Research News
Papers soon-to-be published in Nature Communications
A recent paper authored by several iTHEMS members has been accepted for publication in Nature Communications. The authors from iTHEMS include Hirotaka Ito (ABBL /iTHEMS), Shigehiro Nagataki (ABBL/iTHEMS) and Don Warren (iTHEMS). Congratulations! There will be a press release. Here is the explanation on the article by Hirataka Ito: "The photospheric origin of the Yonetoku relation in gamma-ray bursts” by Hirotaka Ito, Jin Matsumoto, Shigehiro Nagataki, Donald C. Warren, Maxim V. Barkov & Daisuke Yonetoku Accepted for publication in Nature Communications. arXiv:1806.00590 Gamma-ray bursts (GRBs), an intense flash of gamma-rays that is observed almost every day, are the brightest event in the Universe. Decades of studies have revealed that they are originating from a relativistic jet launched at the death of massive star. However, exactly how the gamma-rays are emitted from the jet is still veiled in mystery. One unresolved question is the origin of the correlation between the spectral peak energy and peak luminosity discovered in observations. This “Yonetoku relation” is the tightest correlation found in the properties of GRB emission, providing the best diagnostic for the emission mechanism. In this study, we focused on the so-called “photospheric emission” model which is one of the leading models for the emission mechanism of GRBs. To test the validity of the model, global dynamics of relativistic jet and radiation transfer must be taken into account. To tackle this issue, we performed three-dimensional relativistic hydrodynamical simulations and radiation transfer calculations to evaluate photospheric emission from relativistic jet that is breaking out of massive star envelope. Our simulations revealed that the Yonetoku relation is reproduced as a natural consequence of the jet-stellar interactions. This result strongly suggests that photospheric emission is the emission mechanism of GRBs.
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2019-03-11
Person of the Week
Self-introduction: Ryosuke Iritani
Hi, what's up! I'm Ryosuke (Ryo) Iritani. I'm originally from Kobe and did my biology and math undergrad at Kyoto University in Japan. I started my Ph.D. with Yoh Iwasa at Kyushu University in 2011 and worked as a research fellow (DC1) from 2013, visiting Lausanne (Switzerland) and Montpellier (France) to improve my theoretical skills. I then received Ph.D. in 2016 and started my postdoc at the University of California, Berkeley (as a fellow at the University of Exeter, the UK). I am broadly interested in the field of evolutionary ecology, with a special focus on evolutionary game theory in structured populations. I usually start with my modelings with a motivation to understand ecological phenomena, but I am really keen on developing the general theory of evolutionary ecology. I believe scientific collaboration is the prerequisite to do "good" science, and am therefore always open to collaboration opportunities. My current office is at Kyoto University, so please come talk to me. I like coffee, soccer, typographical fonts, cooking, math, and living organisms (with a special passion for insects).
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2019-03-06
Featured Paper of the Week
Paper: Non-sinusoidal Waveform in Temperature-Compensated Circadian Oscillations
We have autonomous daily rhythm in our body, so-called “circadian clock” for which we can wake up without alarm clock. The rhythm governs the timing of physiological events such as hormone secretion. Curiously, the period of our daily rhythms is stable to temperature, a phenomenon known as “temperature compensation.” Temperature compensation has been a mystery for many years because underlying reaction processes tend to accelerate with temperature. If our internal clock was sensitive to temperature, the clock would not function properly any more. To uncover the mystery, we developed a simpler model of circadian clock based on experimental evidences whilst many realistic simulators have been proposed. Using the model, we derived the period formula. The formula states that “the more non-sinusoidal, the longer period.” From the formula, we predicted that more non-sinusoidal waveform at higher temperature should be observed in reality which is necessary to cancel out the period shortening effect at higher temperature. Unexpectedly, we obtained a similar period formula for a limit cycle oscillation of electrical circuit (van der Pol model), indicating that non-sinusoidal waveform lengthens period. How can circadian clock and electrical circuit behave similarly? We wish to understand the reason in a future.
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2019-03-06
Hot Topic
RIBF “Hodan-kai” meeting on the future of exotic nuclear physics
The second in the series of the RIBF “Hodan-kai” meeting by the young researchers was held at Kobe campus of RIKEN, Integrated Innovation Building, from Feb.18 to 20, 2019. This meeting is aimed at an intensive discussion based on a pure curiosity such as what is interesting and what we want to do in the future in a frank and low-pressure atmosphere. In this meeting, there were 42 participants. We had stimulating talks (14 for invited and 11 for contributed) and discussions not only on the future of nuclear physics with RIBF but also on its related fields: Deep learning, Quantum computing, Computational physics, Weak measurement, Super-heavy elements, Hadron physics, and Laser physics. Following the success of this time, we are planning to hold the next meeting in February 2020, and welcome many young researchers to join.
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2019-03-01
Seminar Report
Report 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 long-term 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 non-specialist to understand, we enjoyed active discussion.
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2019-02-28
Hot Topic
iTHEMS NOW and NEXT
The in-house gathering entitled iTHEMS NOW and NEXT was held on February 26th. This is the occasion we share current status and future perspectives on our research and organization. In the morning, keynote overview talks were given by Kubota, Fawcett, Kurosawa, Yokokura and Taki. Despite her busy schedule, one of our science advisors, Prof. Kotani managed to attend some talks. Another science advisor Prof. Mori also took time to connect through Skype from Kyoto and gave us some important advice. The afternoon session started with the panel discussion facilitated by Warren, and paneled by Chacha, Fawcett, Furusawa, Miyazaki and Y. Inoue. Both at the morning talks and the afternoon discussion, candid opinions were enthusiastically exchanged. After the panel discussion, three presentations on inter-organizational cooperation by Hatsuda, Nagataki, and Prof. Uchiyama from Rikkyo University. Everybody in attendance seemed happy to have the opportunity to express her/his opinion on iTHEMS organization. If you could not attend, you can still click the link shown below for your input.
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2019-02-28
Person of the Week
Self-introduction: Yuki Koyanagi
Hi everyone. My name is Yuki Koyanagi and I am a visiting student at iTHEMS. My research interest is the study of protein structures, specifically how we can predict local structures of a protein from its sequence of amino acid residues. Knowing the structure of protein is important, because we know that a protein's function is highly dependent on its structure. A protein is made up of lots of amino acids connected like a chain, which then folds itself to a three-dimensional structure. One of the important factors that determine the folding is hydrogen bonds, that form at different places along the chain. I am looking into how we can predict the structure around each hydrogen bond. Another related question is finding out how many different hydrogen bond structures are possible for a given sequence of amino acids. I am a mathematician and work at a mathematics research centre, the interdisciplinary environment at iTHEMS is something new to me. I am very excited about the opportunity of meeting people from different fields with different backgrounds.
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2019-02-21
Press Release
Non-sinusoidal Waveform in Temperature-Compensated Circadian Oscillations
Shingo Gibo (Postdoctoral Researcher, iTHEMS) and Gen Kurosawa (Senior Research Scientist, iTHEMS) have published a press release.
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2019-02-08
Hot Topic
Summary of RIKEN-Berkeley workshop on Quantum Information Science (RB19)
RIKEN-Berkeley workshop on Quantum Information Science was held at Lawrence Berkeley National Lab. (building 66) from Jan.26 through 29, 2019. The workshop was started with general introductions to LBNL, RIKEN, iTHEMS and Berkeley Quantum by Horst Simon, Motoko Kotani, Tetsuo Hatsuda and Jonathan Carter, respectively. Then we had stimulating talks and discussions on quantum computing, quantum materials and quantum sensing during the scientific sessions, followed by a panel discussion on the future collaborations between RIKEN and UCB/LBNL. We are going to explore further collaborations on the basis of the discussions of the workshop. The program and the presentation slides can be seen from the related links below. It should be remarked here that Jason Chang (iTHEMS Research Scientist) played essential roles to plan and organize the workshop, which is very much appreciated. Photos: Horst Simon (LBNL) Motoko Kotani (RIKEN) Tetsuo Hatsuda (iTHEMS) Jason Chang (iTHEMS/LBNL) Seigo Tarucha (Tokyo/RIKEN) Hidetoshi Nishimori (TIT)
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2019-02-07
Featured Paper of the Week
Quantum annealing for polynomial systems of equations
The advent of Noisy Intermediate-Scale Quantum (NISQ) quantum computers has galvanized efforts towards discovering near-term applications. An algorithm for solving polynomial systems of equations was proposed by Dr. Chang (iTHEMS) in collaboration with Dr. Gambhir (Lawrence Livermore National Lab), Dr. Humble (Oak Ridge National Lab), and Dr. Sota (R-CCS) and implemented a linear solver on a D-Wave quantum annealer. While the problems are currently limited to sizes that are easily solved by classical computers, the team showed that the quantum algorithm exhibits constant scaling with increasing condition number, in direct contrast with classical methods. Additionally, the quantum algorithm may also be applied iteratively to exponentially decrease the relative residual, allowing for the classical solution to be reproduced by the quantum computer to single precision. However, the scaling with problem size is unfortunately exponentially bad, reflecting limitations of current quantum computers. Fortunately, there is a great amount of interest and effort put fourth by the greater quantum annealing community geared towards tackling this problem, including using inhomogeneous driving fields, reverse annealing, and even hardware developments towards universal quantum annealers.
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2019-01-31
Featured Paper of the Week
Back Reaction of 4D Conformal Fields on Static Geometry
In classical mechanics, a black hole is described by a vacuum solution with the horizon of the Einstein equation. For spherical case, it is the Schwarzschild metric, and the location of the horizon is given by the Schwarzschild radius. (Note that the Schwarzschild radius can also be defined even for a star without horizon.) In quantum mechanics, a black hole evaporates and information inside it seems to be lost, which is contradict to the principle of quantum mechanics. An effective way to address this problem is to consider again “What is the black hole in quantum mechanics?” In this paper, we examined how robust the use of the Schwarzschild metric to represent a black hole is in quantum mechanics. We consider conformal matters (e.g. electromagnetic field) and introduce the quantum effect (4D conformal anomaly) into the Einstein equation, which necessarily makes the equation non-vacuum. We start from the Schwarzschild metric, add the quantum effect perturbatively, and solve the Einstein equation in a self-consistent manner. Then, we showed that the quantum effect can play a crucial role in shaping the static geometry near the Schwarzschild radius. The geometry depends on a parameter corresponding to a boundary condition, and the existence of the horizon requires the fine-tuning. Therefore, in quantum mechanics, a typical static spherical solution does not have a horizon.
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2019-01-22
Featured Paper of the Week
Index theory and topological phases of aperiodic lattices
The paper studies the interactions between dynamical systems, represented via groupoid operator algebras, and index theory, described using Kasparov's bivariant K-functor. The key motivating example is the dynamical systems associated to Delone sets. Delone sets give a model of aperiodic atomic configurations, where the material may be amorphous or quasi-crystalline. The atomic configuration does not have a group structure, but key properties can be encoded in a discrete groupoid. We construct bivariant K-cycles, a generalisation of K-theory classes, that encode the dynamics of the aperiodic lattice. For the case of quasi-crystalline configurations, we obtain finer information coming from the long-range aperiodic order of the material. We then use our constructed K-cycles to define bulk topological phases of aperiodic materials. A bulk-boundary correspondence is also shown, which arises from factorisation properties of the constructed K-cycles.
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2019-01-17
Person of the Week
Self-introduction: Hiroyasu Miyazaki
Hello, everyone! My name is Hiroyasu Miyazaki. I am a mathematician. I mainly study algebraic varieties, which are geometric objects formed by the solutions of algebraic equations. To capture some essential information on algebraic varieties, it is useful to consider their group-theoretic incarnations, called (co)homology groups. Among the many versions of cohomologies, there is a universal one: the motive theory. It has been used to study common properties of cohomologies and their relationship. However, it has been observed that the motive theory loses some important arithmetic information of algebraic varieties. I am trying to overcome this problem by generalizing the motive theory. I was a member of iTHES in 2017. After that, I stayed at IMJ-PRG in Paris for one year, and came back to iTHEMS. I am really glad to join you again, and looking forward to many exciting discussions!
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2019-01-11
Hot Topic
New Year's Greetings from Program Director of iTHEMS
Happy New Year! It has passed more than 2 years since iTHEMS was started on Nov.1, 2016. Now, iTHEMS has almost 60 core members and 4 satellite offices in Kobe, Kyoto, Sendai and Berkeley as well as the main office in Wako. In the last few years, there is a growing interests in mathematical sciences in academia, industry and society. This is encouraging for us to explore further interdisciplinary interactions in science. I hope iTHEMS can continue to provide you with a good research environment, while you continue to provide iTHEMS with a good atmosphere.
118 news in 2019