Colloquium

How is turbulence born: Statistical mechanics and ecological collapse in transitional fluids

April 22 at 15:00 - 16:30, 2022

Dr. Hong-Yan Shih (Assistant Research Fellow, Institute of Physics, Academia Sinica, Taiwan)

The onset of turbulence is ubiquitous in daily life and is important in various industrial applications, yet how fluids become turbulent has remained unsolved for more than a century. Recent experiments in pipe flow finally quantified this transition, showing that non-trivial statistics and spatiotemporal complexity develop as the flow velocity is increased. Combining numerical simulations of the hydrodynamics equations and an effective theory from statistical mechanics, we discovered the surprising fact that fluid behavior at the transition is governed by the emergent predator-prey dynamics, leading to the mathematical prediction that the laminar-turbulent transition is analogous to an ecosystem on the edge of extinction. This prediction demonstrates that the laminar-turbulent transition is a non-equilibrium phase transition in the directed percolation universality class, and provides a unified picture of transition to turbulence in various systems. I will also show our recent progresses on transitional turbulence, including how an extended ecological model with energy balance successfully recapitulates the spatiotemporal patterns beyond the critical point, and the determination of the critical behavior and an emergent novel phase under interactions in the experimental collaboration.

Venue: via Zoom

Event Official Language: English

The 19th MACS Colloquium

April 18 at 15:00 - 17:40, 2022

Dr. Yasuhiro Inoue (Professor, Department of Micro Engineering, Graduate School of Engineering, Kyoto University)

15:00- The 19th MACS Colloquium: Talk by Prof. Yasuhiro Inoue "Multicellular Dynamics Simulation of Morphogenesis" 16:05- MACS SG information session 17:10- Individual explanation by each study group (Zoom breakout room)

Venue: via Zoom

Event Official Language: Japanese

The 18th MACS Colloquium

February 14 at 15:00 - 17:30, 2022

Prof. Tetsuya Nagata (Professor, Physics and Astronomy, Kyoto University, Graduate School of Science)

15:00- Talk by Prof. Tetsuya Nagata 16:05- 2021 MACS Result Briefing 16:30- Discussion

Venue: via Zoom

Event Official Language: Japanese

The 17th MACS Colloquium

November 19 at 15:00 - 18:00, 2021

Prof. Momoko Hayamizu (Assistant Professor, Faculty of Science and Engineering, School of Fundamental Science and Engineering, Waseda University / PRESTO Researcher, Japan Science and Technology Agency (JST))
Dr. Shigeru Kuratani (Chief Scientist, Evolutionary Morphology Laboratory, RIKEN Cluster for Pioneering Research (CPR) / Team Leader, Laboratory for Evolutionary Morphology, RIKEN Center for Biosystems Dynamics Research (BDR))

15:00- Talk by Prof. Momoko Hayamizu 16:15- Talk by Dr. Shigeru Kuratani 17:15- Discussion

Venue: via Zoom

Event Official Language: Japanese

High-Energy Neutrino Astrophysics in the Multimessenger Era

October 28 at 15:00 - 16:30, 2021

Prof. Kohta Murase (Associate Professor, Pennsylvania State University, USA)

The discovery of high-energy cosmic neutrinos opened a new window of astroparticle physics. Their origin is a new mystery in the field, which is tightly connected to the long-standing puzzle about the origin of cosmic rays. I will give an overview of the latest results on high-energy neutrino and cosmic-ray observations, and demonstrate the power of "multimessenger" approaches. In particular, I will show that the observed fluxes of neutrinos, gamma rays, and extragalactic cosmic rays can be understood in a unified manner. I will also highlight the recent developments about astrophysical neutrino emission from supermassive black holes and violent transient phenomena. Possibilities of utilizing high-energy neutrinos as a probe of heavy dark matter may be discussed.

Venue: via Zoom

Event Official Language: English

Finding Gravitational Waves from the Early Universe

September 27 at 16:00 - 17:30, 2021

Prof. Eiichiro Komatsu (Director, Max Planck Institute for Astrophysics, Germany)

The Cosmic Microwave Background (CMB) gives a photographic image of the Universe when it was still an “infant”. We have been using it to test our ideas about the origin of the Universe. The CMB research told us a remarkable story: the structure we see in our Universe such as galaxies, stars, planets, and eventually ourselves originated from tiny quantum fluctuations in the period of the early Universe called cosmic inflation. While we have accumulated strong evidence for this picture, the extraordinary claim requires extraordinary evidence. The last prediction of inflation that is yet to be confirmed is the existence of primordial gravitational waves whose wavelength can be as big as billions of light years. To this end we have proposed to JAXA a new satellite mission called LiteBIRD, whose primary scientific goal is to find signatures of gravitational waves in the polarisation of the CMB. In this presentation we describe physics of gravitational waves from inflation, and the LiteBIRD proposal.

Venue: via Zoom

Event Official Language: English

Quantitative Population Dynamics in Interdisciplinary Biology

July 8 at 10:30 - 12:00, 2021

Prof. Shingo Iwami (Professor, Division of Biological Science, Graduate School of Science, Nagoya University)

Through the course of life, from the moment of birth till death, an organism will achieve various states of equilibrium or ‘homeostasis’ which will inevitably encounter perturbations. The processes of cell growth, differentiation, infection, mutation, evolution and adaptation work together as a coordinated ‘system’, described by mathematical models for population dynamics, to maintain a healthy state. Any disruptions to this system leads to disease including infection, allergy, cancer, and aging. We are conducting interdisciplinary research to elucidate “Quantitative Population Dynamics” through the course of life with original mathematical theory and computational simulation, which are both our CORE approach. Our mathematical model-based approach has quantitatively improved a current gold-standard approach essentially relying on the statistical analysis of “snapshot data” during dynamic interaction processes in life sciences research. In this talk, I will explain how our interdisciplinary approach extends our understanding for complicated clinical data and apply real world problem with an example of the Novel Coronavirus Disease, COVID-19.

Venue: via Zoom

Event Official Language: English

The 16th MACS Colloquium

July 5 at 15:00 - 18:00, 2021

Prof. Yoshitaka Tanimura (Professor, Department of Biophysics, Kyoto University, Graduate School of Science)
Prof. Hidetoshi Nishimori (Senior Visiting Scientist, iTHEMS / Specially Appointed Professor, Tokyo Institute of Technology)

15:00- Talk by Prof. Yoshitaka Tanimura 16:15- Talk by Prof. Hidetoshi Nishimori 17:15- Discussion

Venue: via Zoom

Event Official Language: Japanese

The 15th MACS Colloquium

April 23 at 15:00 - 17:30, 2021

Prof. Hiroshi Ishikawa (Professor, Faculty of Science and Engineering, Waseda University)

15:00- Talk by Prof. Hiroshi Ishikawa 16:05- MACS Student Conference FY2021

Venue: via Zoom

Event Official Language: Japanese

Mirror symmetry and KAM theory

April 16 at 13:30 - 15:00, 2021

Prof. Kenji Fukaya (Permanent Member, Simons Center for Geometry and Physics, Stony Brook University, New York, USA)

13:30pm-15:00pm (JST) Mirror symmetry is a phenomenon discovered in String theory and is much discussed recently in mathematics especially in the field of complex (algebraic) geometry and symplectic geometry. Strominger-Yau-Zaslow found that this phenomenon is closed related to a Lagrangian torus fibration. In an integrable system in Hamiltonian dynamics, the phase space is foliated by Lagrangian tori. I would like to explain a program that the Lagrangian torus fibration found by Strominger-Yau-Zaslow could be regarded as one appearing certain integrable system and KAM theory (which describes a amiltonian dynamics that is a perturbation of an integrable system) could appear in the situation of Mirror symmetry.

Venue: via Zoom

Event Official Language: English

The 14th MACS Colloquium

February 17 at 15:00 - 17:30, 2021

Prof. Yoshihiro Kaneko (Associate Professor, Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University)

15:00- Talk by Prof. Yoshihiro Kaneko 16:05- MACS Report Meeting FY2019 16:30- Discussion of each study group

Venue: via Zoom

Event Official Language: Japanese

Geometry (形); Inconspicuous regulator that determines the fate of cells

December 14 at 10:00 - 11:30, 2020

Prof. Sungrim Seirin-Lee (Professor, Hiroshima University)

December 14 at 10:00-11:30, 2020 (JST) December 13 at 20:00-21:30, 2020 (EST) In the history of mathematical study in pattern formation, the effect of domain has been considered as an important factor that can regulate spatial patterning. However, it is still unknown in biology how the geometry of the domain such as nuclear or cellular shapes can directly regulate the cell fate. In this talk, I will introduce two studies of spatial reorganization in chromatin and cellular dynamics and show that the domain is likely to play a critical role in determining the cell function.

Venue: via Zoom

Event Official Language: English

The Unreasonable Effectiveness of Quantum Theory in Mathematics

November 26 at 10:00 - 11:30, 2020

Prof. Robbert Dijkgraaf (Director, Institute for Advanced Study in Princeton, USA)

November 26 at 10:00-11:30, 2020 (JST) November 25 at 20:00-21:30, 2020 (EST) The physical concepts of quantum theory, in particular of quantum gravity and string theory, have proven to be extremely powerful in addressing deep problems in pure mathematics, from knot invariants to algebraic geometry. Is there such a thing as “quantum mathematics”? Should we add Feynman diagrams, strings, branes and black holes to the language of mathematics?

Venue: via Zoom

Event Official Language: English

The 13th MACS Colloquium

November 13 at 15:00 - 18:00, 2020

Prof. Shin-ya Kawaguchi (Professor, Division of Biological Sciences, Graduate School of Science, Kyoto University)
Dr. Yuji Sugita (Senior Research Scientist, iTHEMS / Chief Scientist, Theoretical Molecular Science Laboratory, RIKEN Cluster for Pioneering Research (CPR))

15:00- Talk by Prof. Shin-ya Kawaguchi 16:15- Talk by Dr. Yuji Sugita 17:15- Discussion

Venue: via Zoom

Event Official Language: Japanese

The 12th MACS Colloquium

July 17 at 15:00 - 18:30, 2020

Prof. Yasuaki Hiraoka (Professor, Kyoto University Institute for Advanced Study (KUIAS) / Team Leader, Topological Data Analysis Team, RIKEN Center for Advanced Intelligence Project (AIP))
Prof. Motomu Tanaka

15:00- Talk by Prof. Yasuaki Hiraoka 16:15- MACS Student Conference FY2020 17:30- Talk by Prof. Motomu Tanaka

Venue: via Zoom

Event Official Language: Japanese

iTHEMS Intensive Course [4] : "Adaptive strategies of organisms, their mathematical bases" - Cancer as a mini-evolutionary process

June 25 at 15:00 - 16:30, 2020

Prof. Yoh Iwasa (Senior Advisor, iTHEMS / Professor, Kwansei Gakuin University)

Living systems exhibit features distinct from nonliving physical systems: their structure and behaviors appear to be chosen adaptive. They are the outcomes of evolution. Mathematical formalisms developed in engineering and social sciences (e.g. control theory, game theory, evolutionary game theory) are sometimes very useful in biology.

Venue: via Zoom

Event Official Language: English

Emergence of life in an inflationary universe

May 11 at 15:30 - 17:00, 2020

Dr. Tomonori Totani (Professor, Department of Astronomy, Graduate School of Science, The University of Tokyo)

The origin of life may be the greatest mystery in natural science. Especially, we know almost nothing about how the first biological molecule (possibly an RNA) appeared from abiotic chemical processes. A widespread notion is that the abiogenesis probability is extremely low when we consider only random chemical reactions to polymerize a large biological molecule. However, we do not know any more efficient polymerization process expected to work in a realistic prebiotic environment. Here, I consider this problem from a viewpoint of cosmology. Cosmologists agree that the universe created by an inflation should extend far beyond the observable universe (13.8 billion light year radius). Then the inflationary universe may be sufficiently large to produce many abiogenesis events, even if we consider only the basic random polymerization. I will give a quantitative answer to this question, and discuss various implications about the origin-of-life studies.

Venue: via Zoom

Event Official Language: English

Interaction Models in Quantum Optics, Representation Theory and Number Theory

April 10 at 15:30 - 17:00, 2020

Dr. Masato Wakayama (Senior Advisor, iTHEMS / Vice President, Tokyo University of Science)

Recently, interaction models originated in quantum optics, with the quantum Rabi model (QRM) as a distinguished representative, are appearing ubiquitously in various quantum systems including cavity and circuit quantum electrodynamics, quantum dots and artificial atoms, with potential applications to quantum information technologies such as quantum computing. Together with the integrability of QRM, demonstrated by Daniel Braak in 2011, this has led to wide discussion and development of various aspect of the QRM and its generalizations from the point of view of theoretical physics and mathematics. In this talk, firstly, we characterize the structure of the spectra of QRM and its asymmetric version via sℓ2-representations. Secondly, we introduce the non-commutative harmonic oscillator, which may be considered to be a “cover” of the QRM in the Heun ODE picture, and describe certain number theoretical aspects arising from its spectral zeta function. Further, we discuss the heat kernel and partition function of the QRM toward the number theoretical investigation of the model. In addition, a number of related open problems will be presented.

Venue: via Zoom

Event Official Language: English

The 11th MACS Colloquium

February 19 at 15:00 - 17:30, 2020

Prof. Hiroyuki Hata (Professor, Graduate School of Science, Kyoto University)

15:00- Teatime 15:15- Talk by Prof. Hiroyuki Hata 16:40- MACS Report Meeting FY2019 The 11th MACS colloquium is supported by iTHEMS. It will be broadcasted to Wako, but if you can join the colloquium physically in Kyoto, that would be better. iTHEMS provides good confectionery at Kyoto!

Venue: Lecture room #401, Graduate School of Science Building No 6, Kyoto University

Event Official Language: Japanese

Exploring the learning principle in the brain

January 16 at 15:30 - 17:00, 2020

Dr. Taro Toyoizumi (Team Leader, RIKEN Center for Brain Science (CBS))

Animals adapt to the environment for survival. Synaptic plasticity is considered a major mechanism underlying this process. However, the best-known form of synaptic plasticity, i.e., Hebbian plasticity that depends on pre- and post-synaptic activity, can surge coincident activity in model neurons beyond a physiological range. Our lab has explored how neural circuits learn about the environment by synaptic plasticity. The instability of Hebbian plasticity could be mitigated by a global factor that modulates its outcome. For example, TNF-alpha that mediates homeostatic synaptic scaling is released by glia, reflecting the activity level of surrounding neurons. I show that a specific interaction of Hebbian plasticity with this global factor accounts for the time course of adaptation to the altered environment (Toyoizumi et al. 2015). At a more theoretical level, I ask what is the optimal synaptic plasticity rule for achieving an efficient representation of the environment. A solution is the error-gated Hebbian rule, whose update is proportional to the product of Hebbian change and a specific global factor. I show that this rule, suitable also in neuromorphic devices, robustly extracts hidden independent sources in the environment (Isomura and Toyoizumi 2016, 2018, 2019). Finally, I introduce that synapses change by intrinsic spine dynamics, even in the absence of synaptic plasticity. I show that physiological spine-volume distribution and stable cell assemblies are both achieved when intrinsic spine dynamics are augmented in a model (Humble et al.2019).

Venue: Large Meeting Room, 2F Welfare and Conference Building (Cafeteria)

Broadcast:R311, Computational Science Research Building / SUURI-COOL (Kyoto) / SUURI-COOL (Sendai)

Event Official Language: English