Our group strives to uncover the basic physics of star formation, planetary systems, active galactic nuclei, the birth of stars and galaxies of the early universe, the characteristics of the light they emit, formation and evolution of galaxies and black holes. We tackle many of the problems of modern astrophysics by solving equations of relativistic radiation hydrodynamics, radiation transport, and gravitational dynamics, which faithfully capture the interaction of light with matter and the complex gravitational interactions, so crucial in the study of the formation and evolution of stars, galaxies, and black holes. To find solutions to the complicated system of equations that describe multi-component celestial bodies and turbulent flow, we conduct large-scale numerical simulations, using, amongst others, tailor-made supercomputers at the Center for Computational Sciences.

## Featured Articles

### [Press release] A cosmological neutrino simulation using Fugaku chosen as a 2021 Gordon Bell Prize finalist

In this research, a completely new method of Vlasov simulation was developed and adopted in a large-scale simulation of the motion of neutrinos in cosmological structure formation. The simulation was run on the entire system of supercomputer "Fugaku". Vlasov simulations can deliver noise-free numerical results compared to conventional N-body simulations,...

## State Transitions and Time Variations of Black Hole Accretion Flows

### Ryoji Matsumoto

Black hole candidates display transitions between hard and soft X-ray states. During the transition, quasi-periodic oscillations and jet ejections are observed, and the black hole accretion flow shows intense activity. Our group has investigated the process of the formation of the soft X-ray emitting region by the cooling of the hot accretion flow emitting hard X-rays as the disk surface density increases, using three-dimensional magnetohydrodynamic and radiative magnetohydrodynamic simulations. We found that a magnetic pressure-dominated accretion disk supported by an azimuthal magnetic field is formed during this transition, and that an increase in the accretion rate leads to radiation pressure...

#### [Press release] The Cosmic Neutrino Background: World's First Six-dimensional Simulations

In this research, we solved the Vlasov-Poisson equations directly by running our new high-precision numerical scheme for...

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#### Theoretical and Observational Astrophysics Joint New Members BBQ

On the 3rd of May 2018, the Theoretical Astrophysics and the Observational Astrophysics groups organized a barbeque...

#### 38th National High School Cultural Festival in Ibaraki "Ibaraki Sobun 2014"

On July 28, 2014, Yu Komatsu was interviewed by students of the newspaper division of the 38th...

#### A fierce new challenge: unveiling the connection between the first galaxies and...

The Epoch of Reionization (EoR) shaped the properties of the baryonic content of the Universe. Using hydrodynamical...

#### Computing the Universe: from Intergalactic to Interstellar Medium

This talk will highlight some progress made based on our efforts of computing the universe, in order...

#### Probing dust aggregate structure in protoplanetary disks by millimeter-wave polarization

Dust coagulation in protoplanetary disks is the first step of planetesimal formation. However, a pathway from dust...

The formation of the first stars after the big bang is one of the most important outstanding...

#### Cosmic Ray Particle Acceleration by the Jet of Microquasar SS433 Probed through...

Since its discovery in the 1970s, the microquasar SS433 has attracted much attention as one of the...

#### The Age of Discovery with JWST: Excavating the First Massive Black Holes...

The James Webb Space Telescope (JWST) is opening a new window of the most distant universe and...

#### Probing the impact of feedback by cosmological hydrodynamic simulations

Observations of the cosmic background radiation have established the $\Lambda$ cold dark matter (CDM) model as the...

#### The Milky Way's central supermassive black hole observed by the Event Horizon...

On May 12, 2022, the Event Horizon Telescope (EHT) Collaboration released the world's first images of the...

#### Formation of Astrophysical Objects 2022

This workshop aims to provide an opportunity to exchange views and share information about the current status...

#### Black-hole jets, accretion discs, and disc-winds workshop 2023

Despite the fact that the existence of black holes is now firmly established, the structure and physical...

#### Galaxy-IGM workshop 2022

The Galaxy-IGM Workshop will be held again this year. For the past 10 years, the Galaxy-IGM Workshop...

#### Formation of Astrophysical Objects 2021

This workshop aims to provide an opportunity to exchange views and share information about the current status...