Coffee Meeting Log
2021-02-12
Active and Passive Phase Separation in a Lattice Model
Kyosuke Adachi (Special Postdoctoral Researcher, iTHEMS / Special Postdoctoral Researcher, Nonequilibrium Physics of Living Matter RIKEN Hakubi Research Team, RIKEN Center for Biosystems Dynamics Research (BDR))
Phase separation is spontaneous segregation into high-density and low-density phases, observed in a variety of systems, e.g., alloy, polymer solution, and intracellular cytoplasm. In this talk, I will review the phase separation phenomena and introduce a model that connects the equilibrium phase separation to another class of separation driven by motility.
2021-02-05
Toward the standard model of elementary particles -- a brief history in 15 min. --
Tetsuo Hatsuda (Program Director, iTHEMS)
I will make a very brief overview on the path toward the modern understanding on the law(s) of fundamental particles.
2021-01-29
Mathematical analysis to smoldering combustion
Shunsuke Kobayashi (Visiting Scientist, iTHEMS / Specially Appointed Assistant Professor, Center for Science Adventure and Collaborative Research Advancement (SACRA), Graduate School of Science, Kyoto University)
Recently, experimental and theoretical study on near-floor flame spreading along a thin solid have been reported. In this talk, I would like to introduce a mathematical model for flame/smoldering fronts, which is equivalent to the Kuramoto--Sivashinsky equation in a scale.
2021-01-22
Is a vacuum empty?
Tsukasa Tada (Coordinator, iTHEMS / Vice Chief Scientist, Quantum Hadron Physics Laboratory, RIKEN Nishina Center for Accelerator-Based Science (RNC))
Usually, a vacuum is a word associated with nothingness. The modern concept of the vacuum, however, exhibits rich and beautiful structure. I will explain the vacuum is the very foundation of our universe.
2021-01-15
Revealing the Neutron Star Properties from Gravitional Wave
Yongjia Huang (International Program Associate, iTHEMS / Ph.D. Student, University of Science and Technology of China, China)
The gravitational wave detection brings us new opportunities to measure the neutron stars' properties. In this talk, I will briefly introduce the process of binary neutron star merger and what we could know from gravitational wave.
2020-12-18
Elucidation of Physics inside Neutron Stars from their Cooling Observations
Akira Dohi (Junior Research Associate, iTHEMS / Ph.D. Student, Department of Physics, Graduate School of Science, Kyushu University)
The densest stars in universe, neutron stars (NSs), cool down due to neutrino losses after their formation. Firstly, I will review about the NS cooling and the representative observations such as Cassiopeia A and possibly NS in supernova 1987A. NS cooling curves are affected by various uncertain physics which may work in NSs. One of the examples is nucleon superfluidty. I will introduce how the neutrons superfluidity can be specified by cooling observations. Another is modified-gravity or beyond-general-relativistic effect. If time is allowed, I also present the possibility to test the theory to describe gravity with use of cooling observations.
2020-12-11
Quasi-steady problem and maximal regularity
Ken Furukawa (Postdoctoral Researcher, iTHEMS / Postdoctoral Researcher, Prediction Science Laboratory, RIKEN Cluster for Pioneering Research (CPR))
I will introduce a brief review of the theory of maximal regularity, and show application to quasi-steady partial differential equations of parabolic type.
2020-11-13
Recent progress in understanding the diversity of eukaryotes based on large scale sequence data-analyses
Euki Yazaki (Postdoctoral Researcher, iTHEMS)
Understanding the phylogenetic relationships of eukaryotes is one of the major research issues in evolutionary biology, since this is the backbone of all eukaryotic evolutionary studies. This research has the history of more than 300 years, and recent statistical analyses using large-scale sequence data has revealed significant progress. I would like to give an overview of the researches for elucidating the phylogenetic relationship of eukaryotes.
2020-10-30
Single polymer chain model: bead spring model
Hiroshi Yokota (Postdoctoral Researcher, iTHEMS)
We frequently meet polymer in our life. For example, DNA in living cells or plastic bag made from polyethylene. In this talk, I will introduce the bead-spring model which is a theoretical model of polymer chain in polymer physics.
2020-10-23
Thomas-Fermi theory
Yukimi Goto (Special Postdoctoral Researcher, iTHEMS)
Although Thomas-Fermi (TF) theory is the original density functional theory, it cannot predict many properties of atoms. I will briefly review the mathematical point of view on the validity of TF theory.
2020-10-16
Toward classification of algebraic varieties
Kenta Sato (Visiting Scientist, iTHEMS / Assistant Professor, Department of Mathematics, Faculty of Mathematics, Kyushu University)
An algebraic variety is a figure defined as the set of solutions of polynomial equations. In this talk, I will briefly explaine recent developments in the classification theory of algebraic varieties.
Public2020-10-09
Planetary lightning: Current State-of-the-art and outstanding questions
Jeremy Riousset (Florida Institute of Technology)
2020-09-25
Instanton Floer homology and TQFT
Masaki Taniguchi (Special Postdoctoral Researcher, iTHEMS)
I would like to review how to construct a TQFT like extension of Donaldson invariant. The main reference is "S. K. Donaldson. Floer homology groups in Yang-Mills theory, Vol. 147 of Cambridge Tracts in Mathematics.".
Public2020-09-18
Collective Power of Science ~ from the High-Energy Atmospheric Physics to our New Exploration of the Universe ~
Teruaki Enoto (Extreme natural phenomena RIKEN Hakubi Research Team)
Lightning discharges and thunderstorms have been recently revealed to exhibit unexpected high-energy phenomena, such as electron acceleration by atmospheric electric fields and photonuclear reactions by gamma rays from accelerated electrons. Our "Extreme natural phenomena RIKEN Hakubi Research Team" is a new group launched in January 2020, and working to create a new interdisciplinary field called the "high-energy atmospheric physics." We are constructing a new observation network for winter thunderclouds along the coast of the Sea of Japan. The heart of this research approach is the "Collective Power of Science". It is an attempt to create science not with a single large instrument, but with a combination of small, scalable instruments. We plan to apply this idea to space X-ray observations using CubeSats and lunar exploration to search for water on its surface using neutron signals generated by cosmic rays. Here I introduce our group activities.
2020-09-11
Neural Turing Machines
Akinori Tanaka (Senior Research Scientist, iTHEMS)
I would like to review how to design 'trainable computer' in the context of recent deep learning techniques: arxiv: 1410.5401
2020-08-07
Peeling tape as a reaction-diffusion system
Keisuke Taga (Waseda Universtiy)
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.
2020-07-31
On the ionization problem
Yukimi Goto (Special Postdoctoral Researcher, iTHEMS)
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.
2020-07-17
Knots in Quantum Field Theory
Toshihiro Ota (Student Trainee, iTHEMS / Ph.D. Student, Graduate School of Science, Osaka University)
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.