Volume 347
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Hot Topic
Farewell message from Rongyang Sun
2025-03-23
Our colleague, Rongyang Sun, will be joining Department of Physics and Astronomy, California State University Northridge, as a postdoctoral researcher, starting April 2025. We will all miss him and wish him the best of luck in this new endeavor.
Here is a message from Rongyang:
I joined iTHEMS in April 2023 as part of RIKEN Quantum, and you may not even meet me on campus as my base is at R-CCS in Kobe. Although my time in iTHEMS has been short, formally only half a year, and I participated in the events remotely most of the time, I learned so much, far more than I expected, from this active research institute, which owns the best diversity and productivity. I would like to thank all the members of iTHEMS, including the directors, researchers, and assistants. Thank you for giving me such a unique experience in my research career!
While I am moving to the US, a physically very far away place, I will continue to follow the development of iTHEMS and share in its success. Starting in April 2025, iTHEMS will be upgraded to a research center. I sincerely wish all the members and the institute greater success in this new era!
Hot Topic
Farewell message from Steffen Backes
2025-03-18
Our colleague, Steffen Backes, will be joining the RIKEN TRIP Research DX Team as an Expert Technician, starting April 1, 2025. We will all miss him and wish him the best of luck in this new endeavor.
Here is a message from Steffen:
I joined iTHEMS and RIKEN in August 2023, so only about 1.5 years ago, but this time had a lasting impression on my personal life and scientific career. It is hard to overstate how much I enjoyed being part of iTHEMS, as it has been an incredibly enjoyable and rewarding time. Being able to meet so many knowledgeable and kind people from different fields and parts of the world, and coming up with new and unconventional ideas due to different backgrounds, was truly amazing. I am very grateful for having been accepted to iTHEMS, which I think is a very special and outstanding place due to this diversity and scientific freedom, that is hard to be found elsewhere.
In FY2025 (April 1st) I will change to an Expert Technician position in the RIKEN TRIP Research DX Team, Wako Campus, so I will still stay close to iTHEMS! As far as time allows, I will make sure to drop by and say hello :)
Thank you everyone for this great time, and let's meet again soon!
Upcoming Events
Seminar
ABBL-iTHEMS Joint Astro Seminar
Fast radio bursts as precursor radio emission from monster shocks
March 21 (Fri) at 16:00 - 17:15, 2025
Arno Vanthieghem (Assistant Professor, Observatoire de Paris and Sorbonne Université, France)
It has been proposed recently that the breaking of MHD waves in the inner magnetosphere of strongly magnetized neutron stars can power different types of high-energy transients. Motivated by these considerations, we study the steepening and dissipation of a strongly magnetized fast magnetosonic wave propagating in a declining background magnetic field, by means of particle-in-cell simulations that encompass MHD scales. Our analysis confirms the formation of a monster shock, that dissipates about half of the fast magnetosonic wave energy. It also reveals, for the first time, the generation of a high-frequency precursor wave by a synchrotron maser instability at the monster shock front, carrying a fraction of 0.1% of the total energy dissipated at the shock. The spectrum of the precursor wave exhibits several sharp harmonic peaks, with frequencies in the GHz band under conditions anticipated in magnetars. Such signals may appear as fast radio bursts.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359, 3F Main Research Building, RIKEN
Event Official Language: English
Seminar
A Century of Quantum Mechanics
March 24 (Mon) at 14:00 - 15:30, 2025
Gordon Baym (Professor Emeritus, University of Illinois, USA)
This is a RIKEN iTHEMS - The Univ. of Tokyo, Phys. Dept. Joint Seminar.
This year, 2025, the "International Year of Quantum Science and Technology (IYQ)," is the 100th anniversary of the "formal" start of quantum mechanics, the description of the microscopic world. 1925 is the year in which Werner Heisenberg and others formulated "matrix mechanics," and physicists began to understand how to accurately predict microscopic phenomena.
In this talk I will describe how quantum mechanics came about, starting with physicists in the late nineteenth century trying to understand the colors of hot metals and other hot objects, noting crucial advances leading to the fully developed wave and matrix quantum mechanics in the mid 1920's, to steps towards understanding real materials, culminating with spectacular applications such as smartphones, scarcely a century later.
Venue: The Univ. of Tokyo, Faculty of Science Building #4, room 1220 / via Zoom
Event Official Language: English
Workshop
Third Workshop on Density Functional Theory: Fundamentals, Developments, and Applications (DFT2025)
March 25 (Tue) - 27 (Thu), 2025
The density functional theory (DFT) is one of the powerful methods to solve quantum many-body problems, which, in principle, gives the exact energy and density of the ground state. The accuracy of DFT is, in practice, determined by the accuracy of an energy density functional (EDF) since the exact EDF is still unknown. Currently, DFT has been used in many communities, including nuclear physics, quantum chemistry, and condensed matter physics, while the fundamental study of DFT, such as the first principle derivations of an accurate EDF and methods to calculate many observables from obtained densities and excited states, is still ongoing. However, there has been little opportunity to have interdisciplinary communication.
On December 2022, we had the first workshop on this series (DFT2022) at Yukawa Institute for Theoretical Physics, Kyoto University, and several interdisciplinary discussions and collaborations were started. On February 2024, we had the second workshop on this series (DFT2024) at RIKEN Kobe Campus, and more stimulated discussion occured. To keep and extend collaborations, we organize the third workshop. Since the third workshop, we extend the scope of the workshop to the development and application of DFT as well. In this workshop, the current status and issues of each discipline will be shared towards solving these problems by meeting together among researchers in mathematics, nuclear physics, quantum chemistry, and condensed matter physics.
This workshop mainly comprises lectures/seminars on cutting-edge topics and discussion, while sessions composed of contributed talks are also planned.
Venue: 8F, Integrated Innovation Building (IIB), Kobe Campus, RIKEN / via Zoom
Event Official Language: English
Seminar
Quantum Gravity Gatherings
Stability of nonsingular black holes
March 27 (Thu) at 15:00 - 16:30, 2025
Shinji Tsujikawa (Professor, Graduate School of Advanced Science and Engineering, Faculty of Science and Engineering, Waseda University)
We show that nonsingular black holes (BHs) realized in nonlinear electrodynamics are always prone to Laplacian instability around the center because of a negative squared sound speed in the angular direction. This is the case for both electric and magnetic BHs, where the instability of one of the vector-field perturbations leads to enhancing a dynamical gravitational perturbation in the even-parity sector. Thus, the background regular metric is no longer maintained in a steady state. We also generalize our analysis to the case in which a scalar field is present besides the U(1) gauge field and find no explicit examples of linearly stable nonsingular BHs. Our results suggest that the construction of regular BHs without instabilities is generally challenging within the scheme of classical field theories.
Venue: Seminar Room #359, 3F Main Research Building, RIKEN / via Zoom
Event Official Language: English
Seminar
iTHEMS Biology Seminar
The rarer-sex effect
March 27 (Thu) at 16:00 - 17:00, 2025
Andy Gardner (Professor, School of Biology, University of St Andrews, UK)
The study of sex allocation—that is, the investment of resources into male versus female reproductive effort—yields among the best quantitative evidence for Darwinian adaptation, and has long enjoyed a tight and productive interplay of theoretical and empirical research. The fitness consequences of an individual's sex allocation decisions depend crucially upon the sex allocation behaviour of others and, accordingly, sex allocation is readily conceptualized in terms of an evolutionary game. I will discuss the historical development of understanding of a fundamental driver of the evolution of sex allocation—the rarer-sex effect—from its inception in the writing of Charles Darwin in 1871 through to its explicit framing in terms of consanguinity and reproductive value by William D. Hamilton in 1972. I will show that step-wise development of theory proceeded through refinements in the conceptualization of the strategy set, the payoff function and the unbeatable strategy.
Venue: #445-447, 4F (Hybrid), Main Research Building, RIKEN / via Zoom
Event Official Language: English
Seminar
iTHEMS Seminar
Omega Meson from Lattice QCD
April 2 (Wed) at 15:00 - 16:00, 2025
Haobo Yan (Ph.D. Student, School of Physics, Peking University, China)
The three-body problem, renowned for its unsolvable nature in celestial mechanics and homonymous science fiction, is not only solvable in the quantum realm regarding spectra but also offers profound insights into QCD. In this talk, I will present the first-ever lattice calculation of the resonance parameters for the lightest hadron decaying into three particles, the -meson. By mapping finite-volume energy levels to infinite-volume scattering amplitude, a pole position trajectory is obtained that, when extrapolated to the physical point, shows good agreement with the experiment.
Venue: Seminar Room #359, 3F Main Research Building, RIKEN / via Zoom
Event Official Language: English
Seminar
Gauge subtleties and the finiteness of loop corrections beyond slow roll
April 3 (Thu) at 14:00 - 15:30, 2025
Danilo Artigas (JSPS Postdoctoral Research Fellow, Department of Physics Ⅱ, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)
The early universe undergoes a phase of exponential expansion called inflation, under which quantum fluctuations are amplified and later seed cosmological structures. A long-standing question is whether interactions of these quantum fields may significantly affect the n-point statistics of cosmological observables. These corrections are known as loop corrections. Recently, Kristiano and Yokoyama claimed that, in scenarios beyond slow-roll inflation, the one-loop correction of super-Hubble fluctuations could become non-negligible and violate cosmological-perturbation theory. This result is highly debated, and in this talk we will use a non-linear approach known as delta N formalism to evaluate these loop corrections. We find the existence of loop corrections for modes close to the Hubble scale, however, these corrections are quickly suppressed for long-wavelength modes. We also show how the result of Kristiano and Yokoyama may arise when truncating the perturbative expansion, and how this result depends on the chosen gauge.
Venue: Seminar Room #359, 3F Main Research Building, RIKEN
Event Official Language: English
Seminar
iTHEMS Biology Seminar
iTHEMS Biology Study Group April Launch Meeting (Part 1)
April 3 (Thu) at 14:00 - 15:00, 2025
Let's launch our Biology Study Group activities for the new year (Part 1 of 2). This meeting will be used to (1) say welcome to new member (SPDR Kenji Okubo, and Postdoc Lucas Sort); (2) discuss Biology seminar management in light of the new iTHEMS Centre; and (3) catch up on each other's current research. Since this will probably take us 2h, this will be Part 1 of 2 (Part 2 on 4/10).
On 4/3 (Part 1) we will get a 15 min introduction talk by SPDR Kenji Okubo.
This meeting is open to all RIKEN and guests. You do not need to be a member of the iTHEMS Biology Study Group.
Venue: via Zoom / 4th floor public space, Main Research Building, RIKEN
Event Official Language: English
Seminar
iTHEMS Seminar
Artificial Intelligence and Neuroscience
April 11 (Fri) at 14:00 - 15:30, 2025
Junichi Chikazoe (Professor, Center for Brain,Mind and KANSEI Sciences Research, Hiroshima University)
Recent advancements in artificial intelligence have led to various discoveries in the field of neuroscience. For example, it has been demonstrated that the information on orientation columns in the visual cortex and the basic taste information in the gustatory cortex can be extracted by applying machine learning to relatively low-resolution functional MRI data. Additionally, intriguing findings have emerged, such as the information processing structures of artificial neural circuits—designed independently of the brain—showing similarities to those of biological neural networks.
In this talk, I will discuss the applications of artificial intelligence in neuroscience and explore future directions in this field.
Venue: Seminar Room #359, 3F Main Research Building, RIKEN / via Zoom
Event Official Language: English
Seminar
ABBL-iTHEMS Joint Astro Seminar
From Galaxies to Cosmological Structures: The Multi-Scale Influence of Cosmic Rays
June 13 (Fri) at 14:00 - 15:15, 2025
Ellis Owen (Special Postdoctoral Researcher, Astrophysical Big Bang Laboratory, RIKEN Pioneering Research Institute (PRI))
Cosmic rays interact with astrophysical systems over a broad range of scales. They go hand-in-hand with violent, energetic astrophysical environments, and are an active agent able to regulate the evolution and physical conditions of galactic and circum-galactic ecosystems. Depending on their energy, cosmic rays can also escape from their galactic environments of origin, and propagate into larger-scale cosmological structures. In this talk, I will discuss the impacts of cosmic rays retained in galaxies. I will show they can deposit energy and momentum to alter the initial conditions of star-formation, modify the circulation of baryons around galaxies, and have the potential to regulate long-term galaxy evolution. I will highlight some of the astrophysical consequences of contained hadronic and leptonic cosmic rays in and around galaxies, and how their influence can be probed using signatures including X-rays, gamma-rays and neutrinos. I will also discuss what happens to the cosmic rays that escape from galaxies, including their interactions with the magnetized large-scale structures of our Universe, and the fate of distant high-energy cosmic rays that do not reach us on Earth.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359, 3F Main Research Building, RIKEN
Event Official Language: English
Colloquium
MACS ColloquiumSupported by iTHEMS
The 28th MACS Colloquium
April 25 (Fri) at 14:45 - 18:30, 2025
Shizuo Kaji (Professor, Institute of Mathematics for Industry, Kyushu University / Professor, Center for Science Adventure and Collaborative Research Advancement (SACRA), Graduate School of Science, Kyoto University)
14:45-15:00 Teatime discussion
15:00-16:00 Talk by Prof. Shizuo Kaji (Professor, Institute of Mathematics for Industry, Kyushu University / Professor, Center for Science Adventure and Collaborative Research Advancement (SACRA), Graduate School of Science, Kyoto University)
16:15-17:20 2024 Study Group introduction session
17:30-18:30 Discussion
Venue: Science Seminar House (Map 9), Kyoto University
Event Official Language: Japanese
Workshop
Recent Developments and Challenges in Tensor Networks: Algorithms, Applications to science, and Rigorous theories
July 28 (Mon) - August 8 (Fri), 2025
Venue: Panasonic Hall, Yukawa Institute for Theoretical Physics, Kyoto University
Register: Event registration form
Event Official Language: English
Upcoming Visitor
March 24 (Mon) - 28 (Fri), 2025 Andy GardnerProfessor, School of Biology, University of St Andrews, UK Visiting Place: RIKEN Wako Campus |
Paper of the Week
Week 4, March 2025
2025-03-20
Title: Pair Correlation Conjecture for the zeros of the Riemann zeta-function I: simple and critical zeros
Author: Daniel Alan Goldston, Junghun Lee, Jordan Schettler, Ade Irma Suriajaya
arXiv: 2503.15449
Title: Frustration-free free fermions
Author: Seishiro Ono, Rintaro Masaoka, Haruki Watanabe, Hoi Chun Po
arXiv: 2503.14312
Title: Stable homotopy theory of invertible gapped quantum spin systems I: Kitaev's Ω-spectrum
Author: Yosuke Kubota
arXiv: 2503.12618
Title: Frustration-free free fermions and beyond
Author: Rintaro Masaoka, Seishiro Ono, Hoi Chun Po, Haruki Watanabe
arXiv: 2503.12879
Title: Modular-invariant random matrix theory and AdS{}_3 wormholes
Author: Jan Boruch, Gabriele Di Ubaldo, Felix M. Haehl, Eric Perlmutter, Moshe Rozali
arXiv: 2503.00101
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