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Rei Nishiura's Homepage

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Email: nishiura[at]tap.scphys.kyoto-u.ac.jp

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About Me

I am currently engaged in theoretical research in high energy astrophysics and plasma physics.

In particular, I am interested in understanding fundamental physical processes such as scattering and instabilities through analytical and numerical approaches, and applying them to astrophysical phenomena such as neutron stars, Fast Radio Bursts (FRBs), and Active Galactic Nuclei (AGNs).

Fields I have worked on (in the order I have focused on)

  1. Plasma physics(scattering, instabilities, kinetic theory)
  2. Electromagnetism(interaction between EM waves and charged particles)
  3. Magnetohydrodynamics(MHD, shocks, turbulence)
  4. Quantum mechanics(quantum mechanical approach to induced scattering)

Through teaching activities (e.g., as a teaching assistant), I have also worked on topics such as protoplanetary disks, gravitational waves, quasinormal modes, and Hawking radiation. More recently, through a collaborative project on Little Red Dots, I have also been working on the physics of stellar structure. In these contexts, I use Newtonian mechanics, special relativity, and general relativity as needed.

You can find my publications here:

Research

Fast Radio Bursts (FRBs)

Fast Radio Bursts (FRBs) are extremely bright radio pulses emitted over millisecond timescales. One of the most promising source candidates is a magnetar, an ultra-strongly magnetized neutron star. A magnetar magnetosphere is filled with electron–positron plasma, and when an intense electromagnetic wave such as an FRB propagates through it, nonlinear wave–plasma interactions can amplify small fluctuations and trigger various instabilities. This physics is crucial for determining whether an FRB can escape or is attenuated during propagation.

I focus in particular on induced scattering, including induced Compton, Brillouin, and Raman processes. I develop analytical theories applicable to ultra-strong magnetic fields and test them through comparisons with kinetic numerical simulations.

First-author papers

  1. Collective Thomson scattering in magnetized electron and positron pair plasma and the application to induced Compton scattering

    Authors: Rei Nishiura, Kunihito Ioka

    Journal: Physical Review D 109, 043048 (2024)

    URL: APS

  2. Induced Compton scattering in magnetized electron and positron pair plasma

    Authors: Rei Nishiura, Shoma F. Kamijima, Masanori Iwamoto, Kunihito Ioka

    Journal: Physical Review D 111, 063055 (2025)

    URL: APS

  3. Unified kinetic theory of induced scattering: Compton, Brillouin, and Raman processes in magnetized electron and positron pair plasma

    Authors: Rei Nishiura, Shoma F. Kamijima, Kunihito Ioka

    Journal: Physical Review D 113, 123070 (2026)

    URL: APS

  4. Induced Scattering of Fast Radio Bursts in Magnetar Magnetospheres

    Authors: Rei Nishiura, Shoma F. Kamijima, Kunihito Ioka

    Status: Submitted (arXiv:2601.18865)

    URL: arXiv

Co-authored papers

  1. One-dimensional PIC Simulation of Induced Compton Scattering in Magnetized Electron-Positron Pair Plasma

    Authors: Shoma F. Kamijima, Rei Nishiura, Masanori Iwamoto, Kunihito Ioka

    Status: Submitted to Physical Review D (arXiv:2601.01169)

    URL: arXiv

Cosmic-Ray Acceleration

Cosmic rays are high-energy charged particles in the Universe. One possible acceleration site is a shock driven by an ultrafast outflow (UFO) from an active galactic nucleus (AGN). Using numerical simulations, I investigate how magnetic-field amplification near shocks, including the Bell instability, affects the acceleration efficiency and maximum energy of cosmic rays.

First-author papers

  1. Bell Instability and Cosmic-Ray Acceleration in Active Galactic Nuclei Ultrafast Outflow Shocks

    Authors: Rei Nishiura, Tsuyoshi Inoue

    Journal: The Astrophysical Journal 997, 175 (2026)

    URL: IOPscience

Little Red Dots

Recently, I have also participated in discussions for a collaborative project on Little Red Dots. While I am not leading this project, I contribute to the collaboration from a theoretical perspective.

Career

Education

Employment

Activities

Teaching Assistant (TA)

Research Group Activities

Invited Talks and International Conference Presentations

Oral and Poster Presentations

B. Oral Presentations

  1. Induced Scattering of Fast Radio Bursts in Magnetar Magnetospheres, 2026 Spring Meeting of the Physical Society of Japan, online, March 2026.
  2. Induced Scattering of Fast Radio Bursts in Magnetar Magnetospheres, 38th Theoretical Astrophysics Symposium “Numerical Simulations and AI in Astrophysics,” University of Tsukuba, December 2025.
  3. Theory of Induced Scattering of Fast Radio Bursts in Magnetar Magnetospheres, High Energy Astrophysics Workshop 2025, Osaka University, Toyonaka Campus, December 2025.
  4. Unified Theory of Induced Scattering of Fast Radio Bursts in Magnetar Magnetospheres, 80th Annual Meeting of the Physical Society of Japan, Hiroshima University, Higashi-Hiroshima Campus, September 2025.
  5. Unified Theory of Induced Scattering of Fast Radio Bursts in Magnetar Magnetospheres, 2025 Autumn Annual Meeting of the Astronomical Society of Japan, Kaikyo Messe Shimonoseki, September 2025.
  6. Unified Theory of Induced Scattering of Fast Radio Bursts in Magnetar Magnetospheres, YITP Workshop “Exploring Extreme Transients: Frontiers in the Early Universe and Time-Domain Astronomy,” Yukawa Institute for Theoretical Physics, Kyoto University, August 2025.
  7. Cosmic-Ray Particle Acceleration in Ultrafast Outflows from Active Galactic Nuclei, High Energy Astrophysics Workshop 2024, Tohoku University, October 2024.
  8. Parametric Decay Instability of Fast Radio Bursts in Magnetar Magnetospheres, 2024 Autumn Meeting of the Physical Society of Japan, September 2024.
  9. Parametric Decay Instability of Fast Radio Bursts in Magnetar Magnetospheres, 2024 Autumn Annual Meeting of the Astronomical Society of Japan, September 2024.
  10. Parametric Instability of Fast Radio Burst in Magnetar Magnetosphere, Keihan Astrophysics Meeting 2024 Fall, Kyoto University, September 2024.
  11. Induced Compton Scattering of Fast Radio Bursts in Magnetized Electron–Positron Pair Plasma, Exploring Extreme Transients: Emerging Frontiers and Challenges, Yukawa Institute for Theoretical Physics, Kyoto University, August 2024.
  12. Thomson Scattering in Magnetized Electron–Positron Pair Plasma and Its Application to Fast Radio Bursts, High Energy Astrophysics Workshop 2023, The University of Tokyo, November 2023.
  13. Scattering of Fast Radio Bursts in Strongly Magnetized Electron-Positron Plasma, YITP Workshop: Cosmic Plasma Revisited, Kyoto University, October 2023.
  14. Collective Scattering of Fast Radio Bursts in Magnetar Magnetospheres, 2023 Autumn Annual Meeting of the Astronomical Society of Japan, Nagoya University, September 2023.
  15. Particle Scattering of Fast Radio Bursts in Magnetar Magnetospheres, 78th Annual Meeting of the Physical Society of Japan, Tohoku University, September 2023.
  16. Scattering of Fast Radio Bursts in Magnetar Bursts, High Energy Astrophysics Workshop 2022, Hiroshima University, November 2022.

C. Poster Presentations

  1. Scattering of Fast Radio Bursts in Strongly Magnetized Electron-Positron Plasma, The Creation of Multi-Messenger Astrophysics, Gero Onsen, December 2023.
  2. Scattering of Fast Radio Bursts in Magnetar Bursts, 35th Theoretical Astrophysics Symposium, Corasse Fukushima, December 2022.
  3. Kilonova Radiation Models for Black Hole–Neutron Star Binary Mergers, 51st Summer School on Astronomy and Astrophysics for Young Researchers, online, August 2021.

Seminars and Presentations

Outreach