Coffee Meeting Log

Date Speaker Title Abstract
2018/04/13 Gilles Ferrand Demonstration of VR system for RIKEN Open Day This will serve as a rehearsal for the ABBL booth at RIKEN Open Day. I may start with a short introduction on how it works, and our goals. Then iTHEMS people can try the experience with the guidance of ABBL members. 
2018/05/11 Catherine Beauchemin Proposed iTHEMS project in virophysics: A web tool to count infectious virus!  I want to propose a fun, simple project for any iTHEMS members to join. The plan is to build a web-based calculation tool which can estimate the concentration of virus in a sample based on some standard measurements. 
2018/05/18 Masato Taki Arithmetic of Words Word2Vec, proposed by googlers in 2013, is a nice numerical representation of a set of words. This vectorial representation realizes arithmetic relation between words. I will briefly explain how this representation is constructed, and demonstrate it by using a text of Plato.
2018/05/25 Wine Meeting

2018/06/01 Tetsuo Hatsuda Life and death of a neutron 1. What is neutron?
2. How it was born in the Universe.
3. How it survives in the Universe.
4. What is the fate of the neutron?
5. Open questions about the neutron. 
2018/06/08 No Talk


about some misuses of statistics in science. 
2018/06/22 Tsukasa Tada A perspective on conformal field theory from Hyperbolic geometry
Gen Kurosawa
On the unsolved mystery of biological clock

Ade Irma Suriajaya
A new theorem on rational triangles

Hiroki Kodama
Positive flat functions cannot be positive forever (via differentiations)

Mamoru Matsuo (Kavli Institute for Theoretical Sciences, UCAS)
Spin hydrodynamic generation: A new power generation at nanoscale

Catherine Beauchemin
A physicist's adventure into the field of Ergonomics

Susumu Inoue
Primordial black hole

Yukinobu Arata (Cellular Informatics Laboratory, RIKEN)
Stochastic and deterministic controls in ageing process

Maria Dainotti
GRB Correlations for GRB Cosmology and machine-learning analysis

Yoshiyuki Inoue
Power of Supermassive Black Hole Jets

Nagisa Hiroshima
Ingredients of gamma-ray searches of dark matter in the Universe

Shunji Matsuura (iQBit)
What is quantum computing?

Yosuke Mizuno (Frankfurt University) Introduction to Black Hole Shadow of M87



2019/6/21 Kohei Kamada (Univ. of Tokyo) On the impact of the chiral anomaly and chiral magnetic effect in the early Universe
2019/6/28 Enrico Rinaldi (Quantum Hadron Physics Lab.) The neutron lifetime puzzle

2019/7/19 Tetsuo Hatsuda (iTHEMS) Preparation for Advisory Council

2019/8/9 Molodij Guillaume (Weizmann Institute) From astrophysics to Biophysics and back
2019/8/23 Eren Mehmet Kıral (API/iTHEMS) On Sensitivity Conjecture
2019/8/30 Takahiro Doi (QHP Lab.) Sign problem in evaluating integral of oscillating function
2019/9/6 Takemasa Miyoshi (RCCS/iTHEMS) On Data Assimilation

2019/9/20 Enrico Rinaldi (QHP Lab.) On Dark Matter
2019/9/27 Andrew Macpherson (IPMU) Derived geometry and topological field theory

2019/10/11 Yoshiyuki Inoue (ITHEMS) Nobel Prize in Physics 2019
2019/10/18 Shingo Gibo (ITHEMS) Biological rhythms and waveform
2019/10/25 Ivan Kostov (Saclay)

2019/11/1 Pascal Naidon (QHP Lab.) The Efimov Effect
2019/11/8 Hajime Sotani (ABBL/iTHEMS)

2019/11/15 Hirotaka Ito (ABBL) The photospheric origin of the Yonetoku relation in gamma-ray bursts
2019/11/22 Tomoki Ozawa (ITHEMS) The new SI units
2019/11/29 Masato Taki (ITHEMS) Pruning brunches of deep learning
2019/12/6 Jeffrey Fawcett (ITHEMS)

2019/12/13 15:30~ Nagisa Hiroshima (ITHEMS) TBA

2020/1/10 Gen Tatara (CEMS/CPR) Spintronics: Spin current propagation or susceptibility?
2020/1/17 Hideshi Ooka (CSRS) Balancing Thermodynamics and Kinetics to Achieve Maximum Rates in Catalysis
2020/1/24 Martin Skrodzki (iTHEMS) Algorithms for point set processes
2020/1/31 Keita Mikami (iTHEMS) Report on RIKEN iTHEMS - Berkeley Math Visiting Scholar Program (Lunch Meeting)

2020/2/14 Hiroki Kodama (iTHEMS/AIMR) On the geodesics of regular polyhedra
2020/2/21 Shane Kelly (Tokyo Institute of Technology) Motivic homotopy theory and modular representation theory



2020/3/27 Takemasa Miyoshi (RCCS/iTHEMS)
(common room w/virtual)
2020/4/3 Haoning He (ABBL) Multi-meesenger Search for sources of high energy neutrino (full virtual start)
2020/4/10 Starter Meeting

2020/4/17 Pascal Naidon On COVID-19 spreading
2020/4/24 Ryusuke Hamazaki (Hakubi TL / iTHEMS) Quantum physicists now study non-Hermiticity

2020/5/8 Ryosuke Iritani (iTHEMS) Next-generation method to derive the basic reproduction number of infectious disease models In response to the recent, increasing interest in epidemiology, I will talk about the mathematical framework to derive the basic reproductive number for compartmental disease models: the Next-Generation Theorem (NGT). In general, whether diseases spread or not is determined by the leading eigenvalue (spectral radius) of a disease-free steady state(s). For an SI-model, for instance, the conventional wisdom is that the instability of (S, I) =(S_0, 0) around the ODE for the model is determined by the real part of the eigenvalue. As the number of infected-class compartments grows, however, it becomes increasingly difficult to determine the spectral radius of the associated matrix. NGT partially resolves this issue by (i) reducing the size of the matrix or dimension, (ii) making the matrix relatively sparse, and (iii) clarifying the biological meaning. I will talk about this theorem per se, though do not give its proof, with some illustrative applications (one of which is actually unsolved and therefore a quiz for you all!) as well as why graph-theory and stochastic analyses may be of great use in the discipline of epidemiology. The purpose of this talk is to facilitate future interactions between biologists including me and theoreticians who are interested in graph theory, matrix calculus, and/or dynamical systems.
2020/5/15 Jeffery Fawcett (iTHEMS) Basics of evolution and the evolution of Sars-CoV-2

2020/5/29 Chin-Kai Chiu (iTHEMS) Knot theory and topological semimetals Topological nodal line semimetals host stable chained, linked, or knotted line degeneracies in momentum space protected by symmetries. We use the Jones polynomial as a general topological invariant to capture the global knot topology of the oriented nodal lines. We show that every possible change in Jones polynomial is attributed to the local evolutions around every point where two nodal lines touch. As an application of our theory, we show that nodal chain semimetals with four touching points can evolve to a Hopf link. We extend our theory to 3D non-Hermitian multiband exceptional line semimetals and provide a recipe to understand the transition of the knot topology for protected nodal lines.
2020/6/5 Tomoya Naito (U Tokyo/QHP) Does Neutron Finite Size Affect Nuclear Structure? Atomic nuclei consist of protons and neutrons, which interact via Coulomb and nuclear interactions. Since protons and neutrons have finite charge radii instead of point particles, these finite-size effects for the Coulomb interaction should be considered in the theoretical calculations. Nevertheless, since the contribution of the Coulomb interaction to the nuclear properties is weaker than that of the nuclear force, it was not considered properly. Recently, we have taken the finite-size effect to the Coulomb interaction into account for the calculation of nuclear structures. We found that the finite-size effects give a non-negligible contribution to the nuclear binding energy [1].
[1] T. Naito, X. Roca-Maza, G. Colò, and H. Liang. Phys. Rev. C Accepted (arXiv:2003.03177).

2020/6/19 Akinori Tanaka (iTHEMS/AIP, Keio) Markdown - the next generation markup language Markdown is a lightweight markup language. Important features are easy to use, beautiful document output, and TeX rendering support. Thanks to these fascinating features, Markdown has been already one of common markup languages at least in engineering perspectives. But, I guess, there will be benefits even in scientific research perspectives. So, I would like to introduce how to use it and its applications.
2020/6/26 Naomi Tsuji (iTHEMS) Observational study of suprenova remnants Supernova remnants, leftovers of supernova explosion, are believed to be factories of heavy elements and high-energy particles (cosmic rays). These ideas can be probed by observations of electromagnetic waves from supernova remnants. I will give a review talk of the observational studies; what we can learn from observations.
2020/7/3 Masaki Taniguchi (iTHEMS) Morse theory and Floer theory In a study of topology, Morse theory provides a way to decompose a manifold into elementary parts. We first review a fundamental method in Morse theory. In Floer theory, we consider infinite-dimensional versions of Morse theory for nice functionals. We explain an idea of Floer theory.
2020/7/10 Catherine Beauchemin (iTHEMS) What should we do about COVID-19? We have been analyzing and modelling the data for COVID-19 cases in Tokyo and Saitama. We have built mathematical models to analyze the data and make predictions about where the case counts can be expected to go next, and what the consequences could be. For a while, things were going better and better, and daily cases were going down. With the increasing case count in Tokyo, Saitama, Osaka, etc., we now have some concerns. We would like an opportunity to show you some of our results and observations and hear your thoughts. How do you feel about the recent increases? If you were in charge, what decision would you take? As scientists, do we have a responsibility to make sure this information is provided to the general public so they have a clear understanding of the situation? We hope you will join us and share your thoughts.
2020/7/17 Toshihiro Ota (iTHEMS) Knots in Quantum Field Theory In our three dimensional space knots (or links) are ubiquitous, not only in physics or mathematics, but also in biology, chemistry etc. (Rather, knots might be more common in biology and chemistry...) When knots appear in our world, they often look too complicated to be classified or distinguished. In this talk I will briefly explain a way to deal with the classification of knots using the general ideas of quantum field theory.
2020/7/31 Yukimi Goto (iTHEMS) On the ionization problem From experiments, it seems that a neutral atom can only bind one or two extra electrons. This is a long standing open problem, sometimes referred to as the ionization conjecture. In this talk, I will briefly present the status of the conjecture.
2020/8/7 Keisuke Taga (Waseda Universtiy) Peeling tape as a reaction-diffusion system When you peel a tape with appropriate velocity, you will find a sierpinski-gascket like fractal pattern on the peeled trace. It is known that this pattern is caused by a switching of a peeling front structure. In this talk, I will introduce a new model of reaction-diffusion system, which can describe this pattern formation.