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

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.

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.

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.

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.

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.

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].

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

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).