Functional Renormalization Group at RIKEN 2023 -From condensed matter and particle physics to gravity-

January 21 (Sat) - 22 (Sun), 2023

Gergely Fejos (Assistant Professor, Institute of Physics, Eötvös Loránd University, Hungary)
Yuya Tanizaki (Special Postdoctoral Researcher, Theory Group, RIKEN Nishina Center for Accelerator-Based Science (RNC) / Assistant Professor, Yukawa Institute for Theoretical Physics, Kyoto University)
Takeru Yokota (Postdoctoral Researcher, The Institute for Solid State Physics (ISSP), The University of Tokyo)
Junichi Haruna (Ph.D. Student, Graduate School of Science, Kyoto University)
Rina Tazai (Assistant Professor, Yukawa Institute for Theoretical Physics, Kyoto University)
Shunsuke Yabunaka (Researcher, Japan Atomic Energy Agency (JAEA))
Taiki Haga (Assistant Professor, Division of Physics and Electronics, Graduate School of Engineering, Osaka Metropolitan University)
Masatoshi Yamada (Assistant Professor, College of Physics, Jilin University, China)

Functional renormalization group (FRG) is a powerful theoretical tool to investigate physical systems described by field theory. Its application covers diverse areas of physics spanning from condensed matter and statistical physics to particle physics and gravity. The purpose of this two-day workshop is to overview the recent applications and progresses of FRG in various fields of physics, to discuss future directions, and to seek for possible new collaborations bridging different fields of physics.

Venue: #345-347, 3F, Main Research Building (Main Venue) / via Zoom

Event Official Language: English

Math and Physics of Seiberg-Witten theory

January 20 (Fri) at 16:00 - 18:10, 2023

Nobuo Iida (JSPS Research Fellow PD, School of Science, Tokyo Institute of Technology)

Math and physics have developed through interactions with each other. For example, classical mechanics and calculous were born together. Einstein's theory of gravitation is written in the language of pseudo-Riemann geometry. Since the late 20th century, physicists centering on Edward Witten have revolutionized modern geometry. Seiberg-Witten theory is one of such breakthroughs, for both mathematicians and physicists. In physics it is regarded as a theory describing strong coupling (i.e. low energy) behavior of some supersymmetric gauge theories. It showes confinement (by a mechanism similar to superconductivity) and electric magnetic duality. Even though this story has not been mathematically justified yet, it is regarded as an important trigger of developments in understanding non perturbative aspects of quantum field theory and string theory, and stimulates broad fields of physics and math. In math, Seiberg-Witten theory is regarded as a fundamental tool to study 3 and 4-dimensional geometry. This is based on a PDE called Seiberg-Witten equation, which originates from the "electric magnetic dual description" of monopoles, but people can use it as a tool to study geometry without knowing such a physical origin. In this talk, developments of Seiberg-Witten theory from both viewpoints will be reviewed and if the time permits, works in math by the speaker and collaborators will be discussed. The speaker thinks it is unusual for a mathematician to talk about something that has not been mathematically justified yet, but hopes this talk will lead to new interactions between math and physics.

Venue: Hybrid Format (Common Room 246-248 and Zoom)

Event Official Language: English

Understanding kilonova spectra and identification of r-process elements

January 20 (Fri) at 14:00 - 15:00, 2023

Nanae Domoto (Ph.D. Student, Department of Astronomy, Graduate School of Science, Tohoku University)

Binary neutron star (NS) merger is a promising site for the rapid neutron capture nucleosynthesis (r-process). The radioactive decay of newly synthesized elements powers electromagnetic radiation, as called kilonova. The detection of gravitational wave from a NS merger GW170817 and the observation of the associated kilonova AT2017gfo have provided with us the evidence that r-process happens in the NS merger. However, the abundance pattern synthesized in this event, which is important to understand the origin of the r-process elements, is not yet clear. In this talk, I will first introduce an overview and current understanding of kilonova. Then, I will discuss our recent findings of elemental features in photospheric spectra of kilonova toward identification of elements.

Venue: via Zoom

Event Official Language: English

Mathematical models inspired by the Lenski experiment

January 19 (Thu) at 10:00 - 11:00, 2023

Adrian Gonzalez-Casanova (Neyman Visiting Assistant Professor, University of California, Berkeley, USA / Associate Professor, National Autonomous University of Mexico, Mexico)

We will discuss the basic models of mathematical population genetics and see how to apply them to the study of the Lenski experiment. Furthermore, we will describe novel models that are capable of providing a parsimonious explanation of the deceleration of the relative fitness and can be used to attack questions such as, is it advantageous to be efficient? If time permits, we will also discuss examples of mathematical modelling beyond the Lenski experiment, including the study of populations of bacteria carrying plasmids.

Venue: via Zoom

Event Official Language: English

Tetra-neutron system studied by RI-beam experiments

January 17 (Tue) at 13:30 - 15:00, 2023

Susumu Shimoura (Research Scientist, Spin isospin Laboratory, RIKEN Cluster for Pioneering Research (CPR))

Multi-neutron systems have attracted a long-standing attention in nuclear physics. In several decades, experimental attempts have been made with a particular focus on the tetra-neutron system. Among them, the two different experiments, the double-charge exchange reaction on 4He and the alpha-particle knockout reaction from the 8He, show a sharp peak just above the threshold in the four-neutron spectra, which could be a signature of a "resonant state", separate from a broad bump structure at higher excitation energy regions. Both the experiments have been realized by using the 8He beam above 150 A MeV at the RIKEN RI Beam Factory. Details of the two experiments including basic idea, experimental techniques, and analysis are presented as well as a historical review of previous experimental attempts. Emphasis is made for the experimental conditions for populating a kinematically isolated tetra-neutron system with very small momentum transfer. The spectral shape is discussed by means of reaction processes and correlations in the final tetra-neutron system with several recent theoretical studies.

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

Event Official Language: English

Mergers of neutron star-neutron star (or black hole) binaries as r-process sites

January 13 (Fri) at 14:00 - 15:00, 2023

Shinya Wanajo (Senior Scientist, Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Germany)

The discovery of an electromagnetic counterpart (kilonova) associated with GW170817 confirms that binary neutron star (NS) mergers are at least one of sites of r-process nucleosynthesis. However, there is no observational evidence that black hole (BH)-NS mergers are r-process sites. In this talk, we overview the latest work of nucleosynthesis based on long-term hydrodynamics simulations of NS-NS and BH-NS mergers covering early dynamical and late post-merger mass ejections. We also briefly discuss a possible constraint on nuclear equations of state.

Venue: via Zoom / Common Room #246-248

Event Official Language: English

Basic of microbial ecology and applicability of your life and research

January 12 (Thu) at 16:00 - 17:00, 2023

Daiki Kumakura (Ph.D. Student, Graduate School of Life Science, Hokkaido University)

Microbial ecology is a fascinating field that examines the various environments in which microbes can thrive and their potential applications to human life. In this seminar, I will delve into four main topics:

Venue: via Zoom

Event Official Language: English

Searching for high-freqeuncy gravitational waves with axion detectors

January 12 (Thu) at 14:00 - 15:30, 2023

Valerie Domcke (Senior Faculty, Department of Theoretical Physics, CERN, Switzerland)

Current gravitational wave (GW) experiments cover a large frequency range from nHz to kHz. Beyond that, the regime of high frequency GWs is both extremely challenging challenging, and highly motivated as a unique window to the very early Universe. In this talk I will discuss a proposal for a new type of electromagnetic GW detector which makes use of the observation that GWs generate oscillating electromagnetic effects in the vicinity of external electric and magnetic fields. This is in close analogy to the interaction of the axion with electromagnetic fields. I will discuss how existing bounds from axion searches can be recast for GWs, as well as implications for future axion searches such as the DMRadio program.

Venue: Hybrid Format (Common Room 246-248 and Zoom)

Event Official Language: English

Can social issues be solved by mathematical science!? - Connecting Corporate Issues and Mathematical Sciences -

January 7 (Sat) at 13:00 - 17:00, 2023

Continuing from last year, we will hold a symposium to explore the possibility of solving social issues through mathematical research. Last year, under the theme of "Social Implementation of Mathematical Research!? - Attempts and Challenges -", we held talks by mathematical scientists working on mathematical problems extracted from corporate issues, and saw that efforts to address issues of interest at the individual researcher level are becoming more active. This year, under the broader theme of "Connecting" mathematical scientists and companies, we will introduce not only researchers who are strongly promoting joint research with companies, but also activities of companies who are collaborating with mathematical scientists from the standpoint of companies. We would like to organize a panel session to share with the participants not only the results of their activities but also the difficulties of the collaboration and the exchange of opinions on how to solve the problems. We are sincerely looking forward to the active participation of corporate researchers and mathematical scientists who are interested in such activities.

Venue: Hybrid Format (Noyori Conference Hall, Nagoya University and Zoom)

Event Official Language: Japanese

A cell membrane model that reproduces cortical flow-driven cell migration and collective movement

January 5 (Thu) at 16:00 - 17:00, 2023

Katsuhiko Sato (Associate Professor, Research Institute for Electronic Science, Hokkaido University)

Cellular migration is a key component of numerous biological processes, including the morphogenesis of multicellular organisms, wound healing, and cancer metastasis, where cells adhere to each other to form a cluster and collectively migrate. Although the mechanisms controlling single-cell migration are relatively well understood, those underlying multiple-cell migration still remain unclear. A key reason for this knowledge gap is the so-called many-body problem. That is, many forces—including contraction forces from actomyosin networks, hydrostatic pressure from the cytosol, frictional forces from the substrate, and forces from adjacent cells—contribute to cell cluster movement, making it challenging to model, and ultimately elucidate, the final result of these forces. In this talk, I provide a two-dimensional cell membrane model that represents cells on a substrate with polygons and expresses various mechanical forces on the cell surface, keeping these forces balanced at all times by neglecting cell inertia. The model is discrete but equivalent to a continuous model if appropriate replacement rules for cell surface segments are chosen. When cells are given a polarity, expressed by a direction-dependent surface tension reflecting the location dependence of contraction and adhesion on a cell boundary, the cell surface begins to flow from front to rear as a result of force balance. This flow produces unidirectional cell movement, not only for a single cell but also for multiple cells in a cluster, with migration speeds that coincide with analytical results from a continuous model. Further, if the direction of cell polarity is tilted with respect to the cluster center, surface flow induces cell cluster rotation. The reason why this model moves while keeping force balance on cell surface (i.e., under no net forces from outside) is because of the implicit inflow and outflow of cell surface components through the inside of the cell. I provide an analytical formula connecting cell migration speed and turnover rate of cell surface components.

Venue: via Zoom

Event Official Language: English