The research team of 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)), Ryosuke Iritani (Research Scientist, iTHEMS) and Ryusuke Hamazaki (Senior Research Scientist, iTHEMS / RIKEN Hakubi Team Leader, Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team, RIKEN Cluster for Pioneering Research (CPR)) have proposed a broadly valid formula for theoretical models of evolutionary and ecological population dynamics using methods from information theory and statistical physics.
The results of this research are expected to lead to a unified framework for understanding complex population dynamics in evolutionary and ecological systems over time.

For more information, please see the related link.

RIKEN iTHEMS and N3AS Physics Frontier Center have started a joint research center, RIKEN-Berkeley Center (RBC), physically located on the 3rd floor of the physics building in Univ. California, Berkeley. This new Center aims to enhance the collaboration on nuclear astrophysics and quantum information science between the two institutions. On May 27-29, 2022, the first annual meeting of N3AS was held in Berkeley together with their international partners, RIKEN iTHEMS and CNRS Centre Pierre Binetruy. iTHEMS members are encouraged to use RBC as a base to interact with researchers in physics, mathematics, biology and related fields at Berkeley.

Ryosuke Iritani (Research Scientist, iTHEMS) is interviewed by The Big Issue Japan, and the latest volume (vol 432) is just published on 1st June.

The Big Issue is a magazine dedicated to supporting people in difficult circumstances and helping them achieve self-reliance. Each issue costs 450 yen, out of which 230 yen is the direct income of the street sales staff.

The content is about mathematical biology and is accessible for anyone. We hope as many people as possible take it a read and support the people!

Yuki Yokokura (Senior Research Scientist, iTHEMS) received "The 13th RIKEN Research Incentive Award (Ohbu Award)" on March 23, 2022 for his outstanding achievement in the "Study of Quantum Black Holes". Congratulations!

Dark matter (DM) is one important ingredient of our Universe of which existence indicates the theory beyond the Standard Model. It is not the unique motivation to extend the Standard Model describing the visible world. For example, we need to explain the origin of the tiny neutrino mass and the matter-antimatter asymmetry. The introduction of sterile neutrinos could solve these problems simultaneously.

Sterile neutrinos are new species of neutrinos which communicate with the Standard Model neutrino (active neutrinos) through mixing. Unfortunately, the possibility of explaining the whole of DM with the sterile neutrinos is already excluded from observations of X-ray emission, neutrino beam experiments, and cosmological requirements. However, it is still a viable candidate when we consider the production mechanism carefully. Furthermore, some of such scenarios expect large lepton asymmetries resulting in the matter-antimatter asymmetry. The sphaleron process takes an important role in such scenarios and it is related to the electroweak phase transition in the early Universe. The process of fixing the lepton asymmetry is interesting: sterile neutrinos first freeze-in, then freeze-out, and decay.

Quantitative prediction of such processes requires sophisticated calculations. Dr. Eijima has shown the latest results in this talk, with the comments that the bottleneck to proceed is the computational costs. The methodology is already well-developed. We will see indicative predictions in the near future! Neutrino physics will open new windows for our Universe!

Reported by Nagisa Hiroshima

Axion-like particles (ALPs) are a class of hypothetical bosons that feebly interact with ordinary matter. The hot plasma of stars and core-collapse supernovae is a possible laboratory to explore physics beyond the standard model, including ALPs. Once produced in a supernova, some of the ALPs can be absorbed by the supernova matter and affect energy transfer. The speaker recently consistently calculated the ALP emission in core-collapse supernovae and the backreaction on supernova dynamics. It is found that the stalled bounce shock can be revived if the coupling between ALPs and photons is as high as $g_{a\gamma}\sim 10^{-9}$ GeV$^{-1}$ and the ALP mass is 40-400 MeV.

Reported by Shigehiro Nagataki

I am Akira Matsumoto. I was in KEK until March 2022 as a student of SOKENDAI and got my Ph.D. there. Then I came to RIKEN and joined iTHEMS as a postdoctoral researcher in May 2022. I am interested in non-perturbative nature of gauge theories such as quantum chromodynamics (QCD), which describes the dynamics of quarks and gluons. Since these elementary particles are building blocks of matter, QCD is the important key to understanding history of our universe. The most powerful method of studying QCD is the Monte Carlo simulation based on the lattice gauge theory. So, we can simulate the dynamics of QCD on a supercomputer. However, in some cases, the Monte Carlo method is not applicable due to the so-called sign problem. For example, QCD with the chemical potential or with the topological theta term suffer from this problem. Since they are related to the structure of neutron star and the strong CP problem, the sign problem is a major obstacle to understanding such phenomena. I am studying and developing methods to avoid this problem. There are some conventional approaches such as the complex Langevin method and the tensor renormalization group. I am also trying to apply recently developing quantum computation to the simulation of gauge theories. I expect we can overcome the sign problem by using these methods in near future.

Title: Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs
Author: Meng Li, Geng Li, Lu Cao, Xingtai Zhou, Xiancheng Wang, Changqing Jin, Ching-Kai Chiu, Stephen J. Pennycook, Ziqiang Wang, Hong-Jun Gao
Journal Reference: Nature (2022)
doi: https://doi.org/10.1038/s41586-022-04744-8

Title: Observing Supernova Neutrino Light Curves with Super-Kamiokande. III. Extraction of Mass and Radius of Neutron Stars from Synthetic Data
Author: Yudai Suwa, Akira Harada, Masayuki Harada, Yusuke Koshio, Masamitsu Mori, Fumi Nakanishi, Ken'ichiro Nakazato, Kohsuke Sumiyoshi, Roger A. Wendell
arXiv: http://arxiv.org/abs/2204.08363v1

Title: Lindbladian Many-Body Localization
Author: Ryusuke Hamazaki, Masaya Nakagawa, Taiki Haga, Masahito Ueda
arXiv: http://arxiv.org/abs/2206.02984v1

Title: Semiclassical Gravity from Averaged Boundaries in two-dimensional BCFTs
Author: Yuya Kusuki
arXiv: http://arxiv.org/abs/2206.03035v1

Title: Evaluations of uncertainties in simulations of propagation of ultrahigh-energy cosmic-ray nuclei derived from microscopic nuclear models
Author: E. Kido, T. Inakura, M. Kimura, N. Kobayashi, S. Nagataki, N. Shimizu, A. Tamii, Y. Utsuno
arXiv: http://arxiv.org/abs/2206.03447v1

Title: Protoneutron Star Convection Simulated with a New General Relativistic Boltzmann Neutrino Radiation-Hydrodynamics Code
Author: Ryuichiro Akaho, Akira Harada, Hiroki Nagakura, Wakana Iwakami, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, Kohsuke Sumiyoshi, Shoichi Yamada
arXiv: http://arxiv.org/abs/2206.01673v1

Title: Semi-analytical frameworks for subhalos from the smallest to the largest scale
Author: Nagisa Hiroshima, Shin'ichiro Ando, Tomoaki Ishiyama
arXiv: http://arxiv.org/abs/2206.01358v1

Title: Ring isomorphisms of type II$_\infty$ locally measurable operator algebras
Author: Michiya Mori
arXiv: http://arxiv.org/abs/2206.00875v1

Title: Universal van der Waals force between heavy polarons in superfluids
Author: Keisuke Fujii, Masaru Hongo, Tilman Enss
arXiv: http://arxiv.org/abs/2206.01048v1