Featured News
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Four Perspectives on Neutron Stars, Pulsars, and Magnetars
The recent work [1] on X-ray bursts from the neutron stars led by our colleague, Akira Dohi (Visiting Scientist, iTHEMS), was featured in the article "Four Perspectives on Neutron Stars, Pulsars, and Magnetars" appeared in Research highlights from the Journals of the American Astronomical Society (see related link below).
2022-12-05
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Universal Force Appearing in Quantum Fluids at Cryogenic Temperatures - Intermolecular Force in Atomic Superfluids Guided by Quantum Fluctuation
The concept of "forces acting between materials," as exemplified by the universal law of gravitation, has continued to occupy an important position in physics. An international research group including Masaru Hongo (Assistant Professor, Faculty of Science, Niigata University / Visiting Scientist, RIKEN iTHEMS) and Keisuke Fujii (Postdoctoral Researcher, University Heidelberg, Germany) have revealed from theoretical calculations that the same intermolecular force known as van der Waals force acts between particles floating in a quantum fluid at cryogenic temperatures over long distances. Atomic groups cooled to near absolute zero (several tens of nano-Kelvin) by laser technology have attracted attention in recent years as a system in which quantum states can be controlled with high precision, and they are an ideal stage for investigating forces in the microscopic world. This research has newly revealed that a universal long-range force due to quantum fluctuation acts on impurity particles in atomic superfluids realized at cryogenic temperatures. For more details, please visit Niigata University's website from the related link below.
2022-12-02
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Naritaka Oshita presented his talk at the 12th Koshien of Science (Oita tournament) on November 3, 2022
The 12th Koshien of Science (Oita tournament), a scientific competition for high school students in Oita prefecture, was held on 3rd November 2022 at Oita city. Naritaka Oshita from iTHEMS presented his talk on “Black Holes Veiled in Mystery” after the competition. More than 200 high school students from Oita prefecture attended. Oshita talked about the history of science, recent progress, and remaining mysteries of black holes. A student asked a unique question “What if we fall into a black hole? Can our consciousness be recovered from the hole?”. Another student asked, “How can it be possible to detect the signal from a ringing black hole?”. The audience enjoyed the stimulating talk and questions from the students. During the competition, Oshita and an iTHEMS assistant Tomoko Iwanami observed the competition, where some students built their toy cars in each group and competed in a race.
2022-11-10
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Science Agora 2022 is held November 4-6, 2022
Science Agora 2022 is held online and in person in the period Nov. 4-6, 2022. There will be many fun sessions that you can join in person or online. There are English sessions too. RIKEN will have a session "Envisioning Futures: Navigating the research landscape with senior women researchers" in which Tetsuo Hatsuda from iTHEMS is one of the speakers. Enjoy !
2022-11-04
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Probing Quark Matter with Gravitational Waves - Reading Traces of Ultra-Dense Matter from Gravitational Waves after Neutron Star Mergers
An international research group including Yongjia Huang (Student Trainee, iTHEMS) and Shigehiro Nagataki (Deputy Program Director, iTHEMS) has performed numerical simulations based on general relativity for the merger of binary neutron stars and shown that the waveform of gravitational waves emitted after the merger provides detailed readings of the properties of ultra dense matter with a density of over 1 trillion kg per cm<sup>3</sup>. This research result is expected to contribute to the clarification of the internal structure of neutron stars and the properties of ultra-dense matter in gravitational wave astronomy. For details, please see the related link.
2022-10-27
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The RIKEN-Berkeley Center was featured in RIKEN Overseas Office Newsletter
The RIKEN-Berkeley Center was featured in the Oct. 2022 issue of "News from RIKEN's Overseas Offices". The title of the article written by Adam Phillips in the RIKEN International Affairs Division is "What makes institutional international collaborations work?". Enjoy the article!
2022-10-25
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Featured articles on iTHEMS published in "Sugaku Tsushin"
iTHEMS was featured in the August volume of "Sugaku Tsushin" (Japanese magazine published by The Mathematical Society of Japan). Our colleagues, Tetsuo Hatsuda, Ade Irma Suriajaya, Yosuke Kubota, Hiroyasu Miyazaki and Yukimi Goto, have written essays on iTHEMS in the volume. Let's see mathematicians' thoughts on the iTHEMS atmosphere.
2022-08-30
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Is it possible to shorten isolation of people infected with new coronavirus? -Development of a simulator to verify the timing of quarantine termination
Professor Shingo Iwami (Graduate School of Science, Nagoya University / Visiting Scientist, iTHEMS), in collaboration with Assistant Professor Keisuke Ejima (Indiana University, USA), has developed a new simulator (computer simulation) to verify when to end isolation of persons infected with a novel coronavirus (COVID-19) through antigen testing. This will allow us to propose a flexible and safe isolation strategy that can terminate isolation of COVID-19-infected patients as early as possible with negative results of a predetermined number of antigen tests. Isolation of infected patients is an important means of preventing the spread of infection. While prolonged isolation reduces the risk of secondary infection, it also places various burdens on the person being isolated and the society that supports them. Using the simulator they have developed, the research group has successfully calculated "the risk of (prematurely) terminating isolation of infectious patients" and "the duration of unnecessary isolation of patients who are no longer infectious (the burden associated with isolation)." As a result, we are now able to propose an appropriate isolation strategy that takes into account individual differences and uses antigen testing to simultaneously reduce risk and burden. As we enter the era of with-colonization, in which social activities are resumed and maintained while infection prevention measures are thoroughly implemented, the successful use of antigen testing will allow for the safe implementation of educational and social activities. In contrast to the current situation where different isolation standards based on clinical and epidemiological data and empirical rules are adopted in different countries, this study is expected to contribute to the establishment of flexible isolation guidelines based on mathematical models, which are required not only in Japan but also worldwide. For more details, please visit the Nagoya University research results dissemination site from the related link.
2022-08-29
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RIKEN Research: Applying quantum speed limits to macroscopic systems
An expression for the maximum speed at which changes in macroscopic systems can occur has been derived by a theoretical physicist at RIKEN. This will deepen our understanding of quantum phenomena in systems that are not in equilibrium. One of the hardest aspects of quantum mechanics to grasp is the Heisenberg uncertainty principle that states that it is not possible to simultaneously pin down both the position and momentum of an object. In other words, the more precisely a particle’s position is determined, the broader the range of its possible momentum becomes (and vice versa). In 1945, two physicists, Leonid Mandelstam and Igor Tamm, focused on another type of the uncertainty relation, namely one between time and energy fluctuation, and showed that transitions in quantum systems don’t happen instantaneously; rather, the speed at which a transition occurs is capped by an amount determined by how much the energy of the system fluctuates. Many other so-called quantum speed limits have subsequently been derived, which have helped better understand the physics of quantum systems and have been useful in various quantum applications. But big problems arise when quantum speed limits are applied to macroscopic systems. “Previous quantum speed limits, which are useful for small systems, typically become meaningless for macroscopic transitions,” notes Ryusuke Hamazaki of the Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team. “For example, conventional quantum speed limits give an infinite upper bound for the speed of transitions in a gas made up of atoms.” To read more, please visit the related link.
2022-08-26
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Oita STEM Festa was held at Oita City
The Oita STEM Festa was held on 23 July 2022 at Oita city and Tetsuo Hatsuda from iTHEMS participated together with members from ADK Corporation. More than 50 high school students from Oita prefecture participated in Course B: "Let's deliver a message 1000 years from now using a black hole recorder” where the black hole recorder produced by the Useless Prototyping Studio was demonstrated. Also, the students were asked to write their Haiku to be recorderd in the black hole recorder. Over 150 high school students participated in the Oita STEM Festa. Course A: "Let's experience the lunar rover!, Course B: "Let's send a message 1000 years from now using a black hole recorder", Course C: "VR technology x solving social issues x SDGs", and Course D: "Let's think about jobs for Oita's future". iTHEMS was represented by Tetsuo Hatsuda and assistants Hitomi Wada and Chikako Ota contributed to the organisation of Course B on site.
2022-08-22
Videos
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What about climate change in actuality?
Odd couples of interdisciplinary research
Khovanov homology theory - an introduction to categorification by Dr. Taketo Sano on May 13, 2022
Fundamentals Fest, mini Pre-event on Science "Exploring and Bridging: The Potential of Basic Science"
In Search of Pc pentaquark - Simulate Hadron Interactions with FUGAKU
AAS Journal Author Series: Hirotaka Ito on 2021ApJ…918...59I
Will Useless Knowledge Change the Future? - What is the Black Hole Recorder?
RIKEN 2019 (in Japanese)
A new B.O.A.T. in astrophysics
Evolution and our daily rhythms
Area law of entanglement entropy in quantum many body systems and its implication in tensor network calculation
Comparison between conventional computers and quantum computers
Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) is an international research program at RIKEN. It facilitates close collaborations among researchers from different disciplines in theoretical, mathematical and computational sciences. The ultimate goal of iTHEMS is to unravel the mystery of the Universe, matter, and life, as well as to solve key problems in modern society through interdisciplinary approaches.
Upcoming Events
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Seminar Today
Quantum kinetics of neutrinos in high-energy astrophysical phenomena
December 9 (Fri) at 14:00 - 15:00, 2022
Dr. Hiroki Nagakura (Specially Appointed Assistant Professor (NAOJ Fellow), Division of Science, NAOJ)
Neutrinos are the most mysterious and elusive particles in the standard model of particle physics. They play important roles in core-collapse supernovae and binary neutron star mergers as driving mass-ejection, synthesizing heavy elements including r-process nuclei, and neutrino signals from these sources. This exhibits the importance of accurate modeling of neutrino radiation field in these phenomena, which will be used to connect neutrino physics to multi-messenger astronomy. It has recently been suggested that neutrino-flavor conversion (or neutrino-oscillation) can ubiquitously occur in these astrophysical environments, exhibiting the requirement of quantum kinetic treatments in the modeling of neutrino transport. In this seminar, I will give an overview of the quantum kinetics neutrino transport and then introduce its recent progress, paying a special attention to the connection to astrophysics. I will also present the latest results of our numerical simulations of collective neutrino oscillations, which can be properly accounted for only by quantum kinetic framework.
Venue: via Zoom
Event Official Language: English
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Seminar
Chiral effects on lepton transport in core-collapse supernovae
December 13 (Tue) at 13:30 - 15:00, 2022
Dr. Di-Lun Yang (Assistant Research Fellow, Institute of Physics, Academia Sinica, Taiwan)
Dynamics of leptons such as electrons and neutrinos play an important role in the evolution of core-collapse supernovae (CCSN). Nevertheless, chirality as one of fundamental microscopic properties that could affect lepton transport, through e.g. weak interaction, has been mostly overlooked. In this talk, I will discuss how chiral effects such as the renowned chiral magnetic effect (CME), generating an electric charge current along magnetic fields with chirality imbalance, could result in the unstable modes of magnetic fields and inverse cascade, which potentially influence the matter evolution in CCSN and pulsar kicks. I will also show how an effective CME could be realized via the backreaction from neutrino radiation even in the absence of an axial charge characterizing an unequal number of right- and left-handed electrons.
Venue: Hybrid Format (Common Room 246-248 and Zoom)
Event Official Language: English
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ColloquiumThe Epidemiology and Economics of Physical Distancing during Infectious Disease Outbreaks
December 14 (Wed) at 11:00 - 12:30, 2022
Prof. Troy Day (Professor, Head of Department, Department of Mathematics and Statistics, Queen's University, Canada)
People's incentives during an infectious disease outbreak influence their behaviour, and this behaviour can impact how the outbreak unfolds. Early on during an outbreak, people are at little personal risk of infection and hence may be unwilling to change their lifestyle to slow the spread of disease. As the number of cases grows, however, people may then voluntarily take extreme measures to limit their exposure. Political leaders also respond to the welfare and changing desires of their constituents, through public health policies that themselves shape the course of the epidemic and its ultimate health and economic repercussions. In this talk I will use ideas from the study of differential games to model how individuals’ and politicians’ incentives change during an outbreak, and the epidemiological and economic consequences that ensue when these incentives are acted upon. Motivated by the COVID-19 pandemic, I focus on physical distancing behaviour and the imposition of stay-at-home orders by politicians. I show that there is a fundamental difference in the political, economic, and health consequences of an infectious disease outbreak depending on the degree of asymptomatic transmission. If transmission occurs primarily by asymptomatic carriers, then politicians will be incentivized to impose stay-at-home orders earlier and for longer than individuals would like. Despite such orders being unpopular, however, they ultimately benefit all individuals. On the other hand, if the disease is transmitted primarily by symptomatic infections, then individuals are incentivized to stay at home earlier and for longer than politicians would like. In this case, politicians will be incentivized to impose back-to-work orders that, despite being unpopular, will again ultimately be to the benefit of all individuals. This is joint work with David McAdams, Fuqua School of Business and Economics Department, Duke University.
Venue: via Zoom
Event Official Language: English
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Seminar
Lattice gauge theory in curved spacetimes
December 15 (Thu) at 14:00 - 15:30, 2022
Dr. Arata Yamamoto (Assistant Professor, Department of Physics, Graduate School of Science, The University of Tokyo)
Lattice gauge theory is a powerful computational approach in quantum field theory. It is also utilizable for investigating quantum phenomena in curved spacetimes, such as rotating frame, torsion, and gravitational backgrounds. In this talk, I would like to overview the formulation and results of lattice simulations in curved spacetimes.
Venue: Common Room #246-248 (Main Venue) / via Zoom
Event Official Language: English
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Seminar
Chemophoresis Engine: Theory of ATPase-driven Cargo Transport
December 15 (Thu) at 16:00 - 17:00, 2022
Dr. Takeshi Sugawara (Project Researcher, Universal Biology Institute, The University of Tokyo)
The formation of macromolecule patterns depending on chemical concentration under non-equilibrium conditions, first observed during morphogenesis, has recently been observed at the intracellular level, and its relevance as intracellular morphogen has been demonstrated in the case of bacterial cell division. These studies have discussed how cargos maintain positional information provided by chemical gradients. However, how cargo transports are directly mediated by chemical gradients remains unknown. Based on the previously proposed mechanism of chemotaxis-like behavior of cargos (referred to as chemophoresis), we introduce the chemophoresis engine as a physicochemical mechanism of cargo motion, which transforms chemical free energy to directed motion through the catalytic ATP hydrolysis [1]. We propose its possible role as a universal principle of hydrolysis-driven intracellular transport.
Venue: via Zoom
Event Official Language: English
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Seminar
Geometric decomposition of entropy production in stochastic and chemical systems
December 16 (Fri) at 13:30 - 15:00, 2022
Mr. Kohei Yoshimura (Ph.D. Student, Department of Physics, Graduate School of Science, The University of Tokyo)
Entropy production is central to understanding nonequilibrium phenomena. It is known that decomposing entropy production enables us to separately treat distinct two aspects of dynamics, nonstationarity and breaking of detailed balance. In this seminar, I talk about our recent progress on geometric decomposition of entropy production in discrete stochastic systems and deterministic chemical systems. For the audience who may not be familiar with nonequilibrium thermodynamics and linear algebraic graph theory, which the latter enables us to treat the two kinds of systems at once, I would like to start with a very basic introduction. Then I explain why and how we decompose entropy production. Specifically, I mainly focus on the "Onsager-projective decomposition" we study in arXiv:2205.15227 rather than the information geometric decomposition provided in the following paper arXiv:2206.14599. Further, several physical consequences will be discussed, including generalization of Schnakenberg's decomposition stemming from cycles in a steady system, and its relation to gradient flow expressions of a master equation and a rate equation.
Venue: via Zoom
Event Official Language: English
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Seminar
Understanding kilonova spectra and identification of r-process elements
January 20 (Fri) at 14:00 - 15:00, 2023
Dr. Nanae Domoto (Ph.D. Student, Department of Astronomy, Graduate School of Science, Tohoku University)
Binary neutron star (NS) merger is a promising site for the rapid neutron capture nucleosynthesis (r-process). The radioactive decay of newly synthesized elements powers electromagnetic radiation, as called kilonova. The detection of gravitational wave from a NS merger GW170817 and the observation of the associated kilonova AT2017gfo have provided with us the evidence that r-process happens in the NS merger. However, the abundance pattern synthesized in this event, which is important to understand the origin of the r-process elements, is not yet clear. In this talk, I will first introduce an overview and current understanding of kilonova. Then, I will discuss our recent findings of elemental features in photospheric spectra of kilonova toward identification of elements.
Venue: via Zoom
Event Official Language: English
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Seminar
Physics-informed deep learning approach for modeling crustal deformation
January 23 (Mon) at 10:30 - 12:00, 2023
Dr. Naonori Ueda (Deputy Director, RIKEN Center for Advanced Intelligence Project (AIP))
The movement and deformation of the Earth’s crust and upper mantle provide critical insights into the evolution of earthquake processes and future earthquake potentials. Crustal deformation can be modeled by dislocation models that represent earthquake faults in the crust as defects in a continuum medium. In this study, we propose a physics-informed deep learning approach to model crustal deformation due to earthquakes. Neural networks can represent continuous displacement fields in arbitrary geometrical structures and mechanical properties of rocks by incorporating governing equations and boundary conditions into a loss function. The polar coordinate system is introduced to accurately model the displacement discontinuity on a fault as a boundary condition. We illustrate the validity and usefulness of this approach through example problems with strike-slip faults. This approach has a potential advantage over conventional approaches in that it could be straightforwardly extended to high dimensional, anelastic, nonlinear, and inverse problems.
Venue: via Zoom
Event Official Language: English
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ColloquiumScaling Optimal Transport for High dimensional Learning
January 24 (Tue) at 17:00 - 18:30, 2023
Dr. Gabriel Peyré (Research Director, CNRS/École Normale Supérieure, France)
iTHEMS-AIP Joint Colloquium Optimal transport (OT) has recently gained a lot of interest in machine learning. It is a natural tool to compare in a geometrically faithful way probability distributions. It finds applications in both supervised learning (using geometric loss functions) and unsupervised learning (to perform generative model fitting). OT is however plagued by the curse of dimensionality, since it might require a number of samples which grows exponentially with the dimension. In this talk, I will explain how to leverage entropic regularization methods to define computationally efficient loss functions, approximating OT with a better sample complexity. More information and references can be found on the website of our book "Computational Optimal Transport" (see related link below).
Venue: via Zoom
Event Official Language: English
Opportunities
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Seeking a few Research Scientists or Senior Research Scientists (W22160)
Deadline: Open until filled
Research Scientist or Senior Research Scientist, a few positions. iTHEMS is seeking Research Scientist(s) or Senior Research Scientist(s) in theoretical astrophysics, astronomy, cosmology, and related fields. The successful applicants are expected not only to pursue top-level research in their own research focus but also to lead interdisciplinary collaborations among different fields such as mathematics, physics, chemistry, biology, information sciences, computational sciences, and social sciences, under the concept of iTHEMS.
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Seeking a few Female Research Scientists or Female Senior Research Scientists (W22158)
Deadline: Open until filled
Female Research Scientist or Female Senior Research Scientist, a few positions. iTHEMS is seeking a few Female Research Scientists or Female Senior Research Scientists to conduct theoretical research in the fields of natural sciences, mathematical sciences, or humanities and social sciences. The scope of responsibilities will be commensurate with the applicant's career level. The applicants will be expected not only to pursue top-level research in their field but also to collaborate actively with an interdisciplinary group of researchers across fields such as mathematics, physics, chemistry, life sciences, engineering, computational sciences, information sciences, and humanity and social sciences, under the concept of iTHEMS.
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Seeking a few Postdoctoral Researchers (W22157)
Deadline: Open until filled
Postdoctoral Researcher, a few positions. We invite applications for postdoctoral researcher positions at RIKEN iTHEMS in the field of theoretical cosmology. The successful applicants are expected not only to conduct high-quality research in their own field but also to participate in interdisciplinary collaborations among different fields including, but not limited to, mathematics, physics, chemistry, life sciences, engineering, computational sciences, information sciences, social sciences, and machine learning sciences, under the concept of iTHEMS.
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Seeking a few Research Scientists or Senior Research Scientists (W22142)
Deadline: Open until filled
Research Scientist or Senior Research Scientist, a few positions. iTHEMS is seeking research scientist(s) or senior research scientist(s) in quantum computational science, quantum information science and related fields. The successful applicants are expected not only to pursue top-level research in their own research focus but also to lead interdisciplinary collaborations among different fields such as mathematics, physics, chemistry, biology, information sciences, computational sciences, and social sciences, under the concept of iTHEMS.
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Seeking a few Research Scientists or Senior Research Scientists (W22141)
Deadline: Open until filled
Research Scientist or Senior Research Scientist, a few positions. iTHEMS is seeking research scientist(s) or senior research scientist(s) in theoretical or applied information science, especially as it pertains to machine learning and data analysis. The successful applicants are expected not only to pursue top-level research in their own research focus but also to lead interdisciplinary collaborations among different fields such as mathematics, physics, chemistry, biology, information sciences, computational sciences, and social sciences, under the concept of iTHEMS.
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Seeking a few Research Scientists or Senior Research Scientists (W22140)
Deadline: Open until filled
Research Scientist or Senior Research Scientist, a few positions. iTHEMS is seeking research scientist(s) or senior research scientist(s) in mathematical sciences including pure mathematics, applied and industrial mathematics. The successful applicants are expected not only to pursue top-level research in their own research focus but also to lead interdisciplinary collaborations among different fields such as mathematics, physics, chemistry, biology, information sciences, computational sciences, and social sciences, under the concept of iTHEMS. This time, we encourage junior applicants who have high ability in mathematical sciences.
Latest News
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2022-12-08
Paper of the WeekWeek 2, December 2022
Title: The density of state method for first-order phase transitions in Yang-Mills theories Author: David Mason, Biagio Lucini, Maurizio Piai, Enrico Rinaldi, Davide Vadacchino arXiv: http://arxiv.org/abs/2212.01074v1
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2022-12-05
Seminar Report
iTHEMS Math Seminar by Dr. Yosuke Matsuzawa on November 11, 2022
On November 11, there was a math seminar by professor Matsuzawa. He gave an introductory talk on the arithmetic dynamical system. He started from simple and interesting examples to some conjectures. Reported by Keita Mikami
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2022-12-05
Seminar ReportMath-Phys Seminar by Dr. Christy Koji Kelly on October 14, 2022
On October 14, there was a joint seminar by Christy Koji Kelly. He gave an introductory talk on the rough geometry. Reported by Keita Mikami
Upcoming Visitors
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Dr. Shinya Wanajo
Visiting Scientist, iTHEMS / Senior Scientist, Max Planck Institute for Gravitational Physics (Albert Einstein Institute), GermanyTerm: December 14 (Wed), 2022 - January 17 (Tue), 2023Visiting Place: RIKEN Wako Campus -
Dr. Masahiro Nozaki
Visiting Scientist, iTHEMS / Assistant Professor, Kavli ITS, ChinaTerm: December 20 (Tue), 2022 - February 7 (Tue), 2023Visiting Place: RIKEN Wako Campus