iTHEMS NOW & NEXT FY2022

March 29 (Wed) at 9:30 - 15:45, 2023

Dr. Eiji Inoue (Special Postdoctoral Researcher, iTHEMS)
Dr. Jeffrey Fawcett (Senior Research Scientist, iTHEMS)
Dr. Hidetoshi Taya (Special Postdoctoral Researcher, iTHEMS)
Dr. Naritaka Oshita (Special Postdoctoral Researcher, iTHEMS)
Dr. Takumi Doi (Senior Research Scientist, iTHEMS)

Program: 9:30-10:00 Keynote Talk by Eiji Inoue 10:00-10:30 Keynote Talk by Jeffrey Fawcett 10:35-11:05 Keynote Talk by Hidetoshi Taya 11:05-11:35 Keynote Talk by Naritaka Ohshita 11:40-12:10 Keynote Talk by Takumi Doi 12:30-13:10 Lunch Time Session on Research Ethics 13:15-13:45 Working Group Report 13:45-14:20 Study Group Report 14:30-15:30 Panel Discussion on future of iTHEMS 15:30-15:45 Concluding Remarks by the Director

Venue: via Zoom

Event Official Language: English

First Chalk

March 29 (Wed) at 16:30 - 17:00, 2023

The occasion to celebrate the launch of the new seminar room will take place after iTHEMS NOW & NEXT.

Venue: Seminar Room #359, Main Research Building

Event Official Language: English

Asymmetric enzyme kinetics of F1-ATPase resulted from asymmetric allosterism

March 30 (Thu) at 16:00 - 17:00, 2023

Dr. Yohei Nakayama (Assistant Professor, Department of Applied Physics, Graduate School of Engineering, Tohoku University)

Bio-molecular machines play various roles in cells where thermal fluctuation is dominant. Since artificial molecular machines are far behind bio-molecular machines for the present, we should begin with understanding how bio-molecular machines are designed to play their roles. We examine the motion of a bio-molecular machine, F1-ATPase, in single molecule experiments. In particular, we focus on the operation of F1-ATPase as ATP synthase in addition to as molecular motor. In this seminar, I talk about the enzyme kinetics, dependence of reaction rate on substrate concentration, of F1-ATPase in ATP synthesis. The experimental result shows that the enzyme kinetics of F1-ATPase in ATP synthesis exhibits weaker dependence on substrate concentration than the ordinary Michaelis-Menten kinetics, whereas that in ATP hydrolysis follows Michaelis-Menten kinetics. Therefore, the enzyme kinetics of F1-ATPase turned out to be asymmetric between ATP synthesis and hydrolysis. We analyzed this asymmetry based on a potential switching model, totally asymmetric allosteric model, whose characteristic is asymmetry in angular dependence of binding rates of substrates. It was shown that the totally asymmetric allosteric model may reproduce the experimental results, where the asymmetry of binding rates is essential. We also discuss physiological roles that the asymmetry of enzyme kinetics may play.

Venue: via Zoom

Event Official Language: English

Gauge-equivariant neural networks as preconditioners in lattice QCD

April 6 (Thu) at 13:30 - 15:00, 2023

Prof. Tilo Wettig (Professor, Universität Regensburg, Germany)

We demonstrate that a state-of-the-art multi-grid preconditioner can be learned efficiently by gauge-equivariant neural networks. We show that the models require minimal re-training on different gauge configurations of the same gauge ensemble and to a large extent remain efficient under modest modifications of ensemble parameters. We also demonstrate that important paradigms such as communication avoidance are straightforward to implement in this framework.

Venue: Common Room #246-248 (Main Venue) / via Zoom

Event Official Language: English

Starter Meeting FY 2023

April 7 (Fri) at 12:30 - 15:00, 2023

At the beginning of a new fiscal year, every member makes a short presentation regarding one's own research.

Venue: via Zoom / Common Room #246-248

Event Official Language: English

An overview on the nuclear equation of state studied from ground and collective excited state properties of nuclei

April 12 (Wed) at 13:30 - 15:00, 2023

Dr. Xavier Roca-Maza (Associate Professor, Department of Physics, University of Milan, Italy)

This contribution reviews a selection of available constraints to the nuclear equation of state (EoS) around saturation density from nuclear structure calculations on ground and collective excited state properties of atomic nuclei [1]. It concentrates on predictions based on self-consistent mean-field calculations, which can be considered as an approximate realization of an exact energy density functional (EDF). Mostly, EDFs are currently derived from effective interactions commonly fitted to nuclear masses, charge radii and, in many cases, also to pseudo-data such as nuclear matter properties. Although in a model dependent way, EDFs constitute nowadays a unique tool to reliablyand consistently access bulk ground state and collective excited state properties of atomic nuclei along the nuclear chart as well as the EoS. The impact on the EoS of the new CREx [2] and PREx [3] measurments of the parity violating asymmetry (ground state observable) in 48Ca and 208Pb, respectively, will be also discussed [4,5] and compared to previously presented results on collective excitations. As the main conclusion, the isospin dependence of the nuclear EoS around saturation density and, to a lesser extent, the nuclear matter incompressibility remain to be accurately determined. Experimental and theoretical efforts in finding and measuring observables specially sensitive to the EoS properties are of paramount importance, not only for low-energy nuclear physics but also for nuclear astrophysics applications.

Venue: 2F Large Meeting Room, RIBF Building, RIKEN Wako Campus (Main Venue) / via Zoom

Event Official Language: English

Emergence of Extreme Universe from Quantum Information

April 17 (Mon) at 16:00 - 17:30, 2023

Prof. Tadashi Takayanagi (Professor, Yukawa Institute for Theoretical Physics, Kyoto University)

Recently, a new interpretation of gravitational spacetime in terms of quantum entanglement has been obtained. The idea of holography in string theory provides a simple geometric computation of entanglement entropy. This generalizes the well-known Bekenstein-Hawking formula of black hole entropy and strongly suggests that a gravitational spacetime consists of many qubits with quantum entanglement. Also a new progress on black hole information problem has been made recently by applying this idea. I will explain these developments in this colloquium.

Venue: via Zoom

Event Official Language: English

Towards EeV Neutrino Astronomy with GRAND

April 18 (Tue) at 14:00 - 15:00, 2023

Dr. Kumiko Kotera (Associate Professor, Institute of Astrophysics, France)

We are living exciting times: we are now able to probe the most violent events of the Universe with diverse messengers (cosmic rays, neutrinos, photons and gravitational waves). One challenge to complete the multi-messenger picture resides in the highest energies, as no ultra-high energy neutrinos have been observed yet. This challenge could be undertaken by the GRAND (Giant Radio Array for Neutrino Detection) project, which aims at detecting ultra-high energy particles, with a colossal array of 200'000 antennas over 200'000 km2, split into ~20 sub-arrays of ~10'000 km2 deployed worldwide. In this talk, we will present preliminary designs and simulation results, plans for the ongoing, staged approach to construction, and the rich research program made possible by the proposed sensitivity and angular resolution.

Venue: Common Room #246-248 / via Zoom

Event Official Language: English

X-ray study on the synchrotron emission in Kepler's SNR

May 19 (Fri) at 14:00 - 15:00, 2023

Dr. Vincenzo Sapienza (Ph.D. Student, Department of Physics, Graduate School of Science, The University of Tokyo)

Synchrotron X-ray emission in young supernova remnants (SNRs) is a powerful diagnostic tool to study the population of high energy electrons accelerated at the shock front. We performed a spatially resolved spectral analysis of the young Kepler's SNR, where we identify two different regimes of particle acceleration. In the north, where the shock interacts with a dense circumstellar medium (CSM), we found a more efficient acceleration than in the south, where the shock velocity is higher and there are no signs of shock interaction with dense CSM. We also studied the temporal evolution of the synchrotron flux, from 2006 to 2014. A number of regions show a steady synchrotron flux and equal cooling and acceleration times. However, we found some regions where we measured a significant decrease in flux from 2006 to 2014. Our results display a coherent picture of the different regimes of electron acceleration observed in Kepler's SNR. Also If I will have time during the seminar it will be nice to present also some preliminary results I will have in the SN 1987A project.

Venue: Common Room #246-248 / via Zoom

Event Official Language: English

Spectral correlations and scrambling dynamics in Sachdev-Ye-Kitaev type models

May 30 (Tue) at 13:30 - 15:00, 2023

Dr. Masaki Tezuka (Assistant Professor, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

Note: Due to unexpected trouble, we have made the decision to postpone the seminar scheduled for February 21 to May 30. Sorry for the trouble. Abstract: The Sachdev-Ye-Kitaev (SYK) model, proposed in 2015, is a quantum mechanical model of N Majorana or complex fermions with all-to-all random four-body interactions. The model has attracted significant attention over the years due to its features such as the existence of the large-N solution with maximally chaotic behavior at low temperatures and holographic correspondence to low-dimensional gravity. The sparse version of the SYK model reproduces essential features of the original model for reduced numbers of disorder parameters. We recently proposed [1] a further simplification, where we set the nonzero couplings to be +1 or -1 rather than sampling from a continuous distribution such as Gaussian. This binary-coupling model exhibits strong correlations in the spectrum, as observed in the spectral form factor, more efficiently in terms of the number of nonzero terms than in the Gaussian distribution case. We also discuss the scrambling dynamics with the binary-coupling sparse SYK model, comparing the model with the original model as well as the SYK model with random two-body terms [2], where the localization of the many-body eigenstates in the Fock space has been quantitatively studied [3,4].

Venue: Common Room #246-248 / via Zoom

Event Official Language: English

g-RIPS-Sendai 2023

June 19 (Mon) - August 8 (Tue), 2023

The Research in Industrial Projects for Students (RIPS) program has been held at the Institute for Pure & Applied Mathematics (IPAM) of the University of California, Los Angeles. In 2018, the Advanced Institute for Materials Research (AIMR) at Tohoku University in Sendai launched the g-RIPS-Sendai program in collaboration with IPAM, targeting graduate-level students in mathematical science and related disciplines. Participants from the U.S. and Japan will work on cross-cultural teams on research projects designed by industrial partners. The projects are expected to be of great interest to the partners and offer stimulating challenges to students. For more information on this year's g-RIPS-Sendai 2023, please visit the program website at the related link. Organizers: Research Alliance Center for Mathematical Science (RACMaS), Tohoku University Tohoku Forum for Creativity (TFC), Tohoku University Advanced Institute for Materials Research (AIMR), Tohoku University In cooperation with the following organizations: RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) Institute for Pure & Applied Mathematics (IPAM), UCLA

Venue: Advanced Institute for Materials Research (AIMR), Tohoku University

6th Workshop on Virus Dynamics

July 4 (Tue) - 6 (Thu), 2023

Prof. Catherine Beauchemin (Deputy Program Director, iTHEMS)
Prof. Shingo Iwami (Professor, Graduate School of Science, Nagoya University)

The Workshop on Virus Dynamics is an international meeting held every 2 years. It brings virologists, immunologists, and microbiologists together with mathematical and computational modellers, bioinformaticians, bioengineers, virophysicists, and systems biologists to discuss current approaches and challenges in modelling and analyzing different aspects of virus and immune system dynamics, and associated vaccines and therapeutics. This 6th version of the workshop builds on the success of previous ones held in Frankfurt (2013), Toronto (2015), Heidelberg (2017), Paris (2019) and virtually (2021). It is supported by the Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) program at RIKEN, by Nagoya University, and by the Japan Science and Technology Agency. Up-to-date information and registration is available via the website. The workshop is for in-person participation only (no virtual or hybrid option).

Venue: Noyori Conference Hall, Higashiyama Campus, Nagoya University

Event Official Language: English