Papers

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• "Numerical Studies of Accretion Flows onto a Neutron Star Engulfed in a Massive Star"
  Daiyu Sakurai, Ryuichiro Akaho, Shoichi Yamada
  Submitted to MNRAS, arXiv:2604.19236 
  What's new: wind-tunnel simulation of the neutron star accretion engulfed a massive star, using the multi-layer domain-decomposition to resolve the neutron star scale

• "Comprehensive neutrino light curves and spectra: from pre-supernova evolution to early supernova phase"
  Chinami Kato, Hiroki Nagakura, Akira Ito, Ryosuke Hirai, Shun Furusawa, Takashi Yoshida, Ryuichiro Akaho
  Submitted to the Astrophysical Journal Supplement Series, arXiv:2603.09810  
  What's new: sequential supernova neutrino signal starting from the presupernova phase

• "Bifurcated Impact of Neutrino Fast Flavor Conversion on Core-collapse Supernovae Informed by Multi-angle Neutrino Radiation Hydrodynamics"
  Ryuichiro Akaho, Hiroki Nagakura, Wakana Iwakami, Shun Furusawa, Akira Harada, Hirotada Okawa, Hideo Matsufuru, Kohsuke Sumiyoshi, Shoichi Yamada
  Physical Review Letters 136, 191002 (2026)  Featured in Physics Viewpoint  Press release in EurekAlert  プレスリリース
  What's new: investigate the effect of the neutrino fast flavor instability by implementing multi-angle subgrid modeling onto 2D simulations

• "A Dual-Resolution Prescription in the S_N Method for Boltzmann Neutrino Transport I: Proof of Principle and the Resolution of Collision Term"
  Akira Ito, Ryuichiro Akaho, Hiroki Nagakura, Shoichi Yamada
  The Astrophysical Journal Supplement Series 284 11 (2026)
  What's new: propose a new scheme for the Boltzmann neutrino transport, which employs different momentum angle resolution for advection and collision terms 

• "Neutrino Constraints on Black Hole Formation in M31"
  Yudai Suwa, Ryuichiro Akaho, Yosuke Ashida, Akira Harada, Masayuki Harada, Yusuke Koshio, Masamitsu Mori, Fumi Nakanishi, Ken'ichiro Nakazato, Kohsuke Sumiyoshi, Roger A. Wendell, Masamichi Zaizen
  The Open Journal of Astrophysics, Vol.8 id.167 (2025)
  What's new: nuclear equation of state constraint based on non-neutrino detection from the black hole formation candidate event in M31 galaxy

• "Asymmetric emissions of neutrinos in the cooling of rotating proto-neutron stars"
  Laura Barrio, Kotaro Fujisawa, Ryuichiro Akaho, Hiroki Nagakura, Shoichi Yamada
  Physical Review D 112, 083039 (2025)
  What's new:  asymmetric neutrino emission from the rotating PNS with the Boltzmann transport and the resultant gravitational memory

• "Comparative Testing of Subgrid Models for Fast Neutrino Flavor Conversions in Core-collapse Supernova Simulations"
  Ryuichiro Akaho, Hiroki Nagakura, Shoichi Yamada
  Physical Review D 112, 043015 (2025)
  What's new: implementation of the neutrino fast flavor conversion (FFC) subgrid model onto Boltzmann radiation-hydro code, and comparison of different mixing methods 

• "Observing Supernova Neutrino Light Curves with Super-Kamiokande.VI. A Practical Data Analysis Technique Considering Realistic Experimental Backgrounds"
  Fumi Nakanishi, Ken'ichiro Nakazato, Masayuki Harada, Yusuke Koshio, Ryuichiro Akaho, Yosuke Ashida, Akira Harada, Masamitsu Mori, Kohsuke Sumiyoshi, Yudai Suwa, Roger A. Wendell, Masamichi Zaizen
  The Astrophysical Journal 992 27 (2025)
  What's new:  new backward-time analysis method for SuperK with the realistic background noise taken into account

• "Observing Supernova Neutrino Light Curves with Super-Kamiokande. V. Distance Estimation with Neutrinos Alone"
  Yudai Suwa, Akira Harada, Masamitsu Mori, Ken'ichiro Nakazato, Ryuichiro Akaho, Masayuki Harada, Yusuke Koshio, Fumi Nakanishi, Kohsuke Sumiyoshi, Roger A. Wendell
  The Astrophysical Journal 980 117 (2025)
  What's new: development of the analysis method to infer core-collapse supernova distance only from neutrino signals

• "Quasi-steady evolution of fast neutrino-flavor conversions"
  Jiabao Liu, Hiroki Nagakura, Masamichi Zaizen, Lucas Johns, Ryuichiro Akaho, Shoichi Yamada
  Physical Review D 111, 023051 (2025)
  What's new: behavior of the neutrino fast flavor conversion (FFC) with constantly injected neutrinos that generates persistent appearance of ELN-XLN crossing

• "Impacts of Black-Hole-Forming Supernova Explosions on the Diffuse Neutrino Background"
  Ken'ichiro Nakazato, Ryuichiro Akaho, Yosuke Ashida, Takuji Tsujimoto
  The Astrophysical Journal 975 71 (2024)  
  What's new: estimation of the diffuse supernova neutrino background (DSNB) signal by taking into account the accretion emission from the black hole forming progenitors

• "Muon-induced collisional flavor instability in core-collapse supernova"
  Jiabao Liu, Hiroki Nagakura, Ryuichiro Akaho, Akira Ito, Masamichi Zaizen, Shoichi Yamada
  Physical Review D 110, 043039 (2024)
  What's new: appearance of the resonance-like collisional flavor instability (CFI) due to the presence of muons

• "Physical mechanism of core-collapse supernovae that neutrinos drive"
  Shoichi Yamada, Hiroki Nagakura, Ryuichiro Akaho, Akira Harada, Shun Furusawa, Wakana Iwakami, Hirotada Okawa, Hideo Matsufuru, Kohsuke Sumiyoshi
  Proceedings of the Japan Academy, Series B, Physical and biological sciences 100(3) (2024)
  Review article of core-collapse supernovae 

• “Detectability of Late-time Supernova Neutrinos with Fallback Accretion onto Protoneutron star”
  Ryuichiro Akaho, Hiroki Nagakura, Thierry Foglizzo
  The Astrophysical Journal 960 116 (2024)  Featured in AAS Nova
  What's new: prediction of neutrino signals due to the fallback accretion onto cold proto-neutron star

• "Collisional and Fast Neutrino Flavor Instabilities in Two-dimensional Core-collapse Supernova Simulation with Boltzmann Neutrino Transport"
  Ryuichiro Akaho, Jiabao Liu, Hiroki Nagakura, Masamichi Zaizen, Shoichi Yamada
  Physical Review D 109, 023012 (2024)
  What's new: post-process analysis of the collisional & fast neutrino flavor instabilities in 2D core-collapse supernova model

• "Universality of the Neutrino Collisional Flavor Instability in Core Collapse Supernovae"
  Jiabao Liu, Ryuichiro Akaho, Akira Ito, Hiroki Nagakura, Masamichi Zaizen, Shoichi Yamada
  Physical Review D 108, 123024 (2023)
  What's new: systematic post-process analysis of the collisional neutrino flavor instability in 1D core-collapse supernova models

• “Protoneutron Star Convection Simulated with a New General Relativistic Boltzmann Neutrino Radiation-Hydrodynamics Code”
  Ryuichiro Akaho, Akira Harada, Hiroki Nagakura, Wakana Iwakami, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, Kohsuke Sumiyoshi, and Shoichi Yamada
  The Astrophysical Journal 944 60 (2023)
  What's new: development of general relativistic Boltzmann radiation hydro code and application to the proto-neutron star convection simulations

• “Principal-Axis Analysis of the Eddington Tensor for the Early Post-Bounce Phase of Rotational Core-Collapse Supernovae”
  Wakana Iwakami, Akira Harada, Hiroki Nagakura, Ryuichiro Akaho, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, Kohsuke Sumiyoshi, and Shoichi Yamada
  The Astrophysical Journal 933 91 (2022)
  What's new: comparison of the moment closures in rotating core-collapse supernovae based on momentum space information provided by the Boltzmann transport

• "Multidimensional Boltzmann Neutrino Transport Code in Full General Relativity for Core-collapse Simulations"
  Ryuichiro Akaho, Akira Harada, Hiroki Nagakura, Kohsuke Sumiyoshi, Wakana Iwakami, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, and Shoichi Yamada
  The Astrophysical Journal 909 210 (2021)
  What's new: development of the general relativistic Boltzmann neutrino transport code