Thursday, February 24, 17:00– 18:15 Quantum Matter Seminar
Friday, February 25, 12:30- 13:30 Coffee Meeting
Friday, February 25, 18:00- 18:30 External Event: RIKEN Day: Let's Talk with Researchers! "Listening to the Ringing of a Black Hole"

In the recent article posted in "Quanta magazine”, iTHEMS Director Tetsuo Hatsuda, visiting researcher Tetsuo Hyodo and their collaborator Laura Fabbietti in Munich are interviewed about the ongoing studies on the mysteries of nuclear forces using the Japanese supercomputers and the European Large Hadron Collider (LHC).

See related links for details.

An advanced mathematical model that can describe high-energy interactions between light and matter has been developed by two RIKEN researchers and a collaborator [1]. The approach could be extended to offer new insights in other areas of physics.

High-harmonic generation is a powerful technique that converts laser light from one wavelength, or color, to another. Put simply, it converts a low-energy, long-wavelength photon into multiple higher energy, shorter wavelength photons.

High-harmonic generation has several applications. For example, it offers a way to create table-top sources of extreme ultraviolet or x-ray light using lasers, rather than expensive synchrotron facilities. High-harmonic generation can also produce ultrashort light pulses, as short as one attosecond ($10^{-18}$ second) or maybe even one zeptosecond ($10^{-21}$ second), which are useful for imaging extremely rapid processes such as those that occur in atoms. But high-harmonic generation is inherently difficult to model mathematically, and thus understand fully.

Now, Hidetoshi Taya and Masaru Hongo from the RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) Program, together with their colleague Tatsuhiko Ikeda from the University of Tokyo, have developed an analytical approach to high-harmonic generation in the so-called non-perturbative regime for the first time.

To read more, please visit the related link.

The Hidden Markov Models (HMM) have been used in a variety of fields for different purposes.
I reviewed HMM and basic algorithms such as the forward algorithm. Then, I explained how this statistical framework can be applied to biological problems.

Dr. Yutaka Hirai gave an excellent talk on Galactic archaeology with r-process elements. He showed that his high-resolution simulations of galaxies suggest that binary neutron star mergers play an important role in enriching r-process elements in dwarf galaxies and the Milky Way. He also showed that r-process enhanced stars in the Milky Way tend to form in dwarf galaxies previously accreted to the Milky Way. He demonstrated that the abundance of r-process elements in stars can be used as an indicator for the early evolution of the Milky Way.

Reported by Shigehiro Nagataki

Stochastic processes describe systems in which one or more variables fluctuate randomly. In the first part of the talk, I reviewed basic concepts in stochastic processes and how to express them in terms of localized spin operators and the probability vector (PV). This framework is convenient to compute statistics away from meanfield approximations because it can borrow methods traditionally used in many-body problems in Physics. The second part of the talk addressed the equation for the squared norm of the PV and its correspondence with the Rényi entropy. The general idea and challenges of employing estimates of the Rényi entropy were discussed shortly after. As a practical biological application, I explained the dynamical equations for averages and fluctuations in a simple stochastic epidemic model, highlighting the effects of noise and correlations in heterogeneous finite systems.

Revealing time-resolved particle acceleration in the recurrent Nova RS Ophiuchi
H.E.S.S. Collaboration (Naomi Tsuji)
arXiv: https://arxiv.org/abs/2202.08201

Title: Nonperturbative Waveguide Quantum Electrodynamics
Author: Yuto Ashida, Takeru Yokota, Atac Imamoglu, Eugene Demler
arXiv: http://arxiv.org/abs/2105.08833v4

Title: Isospin symmetry breaking in the charge radius difference of mirror nuclei
Author: Tomoya Naito, Xavier Roca-Maza, Gianluca Colò, Haozhao Liang, Hiroyuki Sagawa
arXiv: http://arxiv.org/abs/2202.05035v1

Title: The double detonation of a double degenerate system, from Type Ia supernova explosion to its supernova remnant
Author: Gilles Ferrand, Ataru Tanikawa, Donald C. Warren, Shigehiro Nagataki, Samar Safi-Harb, Anne Decourchelle
arXiv: http://arxiv.org/abs/2202.04268v1

Title: Detecting Preformed-Pair Current through Nonequilibrium Noise in the BCS--BEC Crossover
Author: Hiroyuki Tajima, Daigo Oue, Mamoru Matsuo, Takeo Kato
arXiv: http://arxiv.org/abs/2202.03873v1