Yamamoto, Naoki

写真a

Affiliation

Faculty of Science and Technology, Department of Physics （Yagami）

Position

Associate Professor

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Career 【 Display / hide 】

  • 2007.04
    -
    2010.03

    東京大学, 大学院理学系研究科, 日本学術振興会 特別研究員 (DC1)

  • 2010.04
    -
    2012.03

    University of Washington, Institute for Nuclear Theory, JSPS Postdoctoral Fellow for Research Abroad / Research Associate

  • 2012.04
    -
    2013.08

    京都大学, 基礎物理学研究所, 日本学術振興会 特別研究員 (PD)

  • 2013.09
    -
    2014.03

    University of Maryland, Maryland Center for Fundamental Physics, Research Associate

  • 2014.04
    -
    2017.03

    慶應義塾大学, 理工学部物理学科, 専任講師

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Academic Background 【 Display / hide 】

  • 2001.04
    -
    2005.03

    The University of Tokyo, 理学部, Department of Physics

    University, Graduated

  • 2005.04
    -
    2007.03

    The University of Tokyo, Faculty of Science, Department of Physics

    Graduate School, Completed, Master's course

  • 2007.04
    -
    2010.03

    The University of Tokyo, Faculty of Science, Department of Physics

    Graduate School, Completed, Doctoral course

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Academic Degrees 【 Display / hide 】

  • 博士（理学）, The University of Tokyo, Coursework, 2010.03

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Research Areas 【 Display / hide 】

  • Natural Science / Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics

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Papers 【 Display / hide 】

  • Generalized chiral instabilities, linking numbers, and non-invertible symmetries

    Naoki Yamamoto, Ryo Yokokura

    Journal of High Energy Physics 07 （ 45 ） 1 - 29 2023.07

    Research paper (scientific journal), Joint Work, Accepted

    　View Summary

    We demonstrate a universal mechanism of a class of instabilities in infrared regions for massless Abelian p-form gauge theories with topological interactions, which we call generalized chiral instabilities. Such instabilities occur in the presence of initial electric fields for the p-form gauge fields. We show that the dynamically generated magnetic fields tend to decrease the initial electric fields and result in configurations with linking numbers, which can be characterized by non-invertible global symmetries. The so-called chiral plasma instability and instabilities of the axion electrodynamics and (4+1)-dimensional Maxwell-Chern-Simons theory in electric fields can be described by the generalized chiral instabilities in a unified manner. We also illustrate this mechanism in the (2+1)-dimensional Goldstone-Maxwell model in electric field.

  • Effective Chiral Magnetic Effect from Neutrino Radiation

    Naoki Yamamoto, Di-Lun Yang

    Physical Review Letters 131 （ 1 ） 012701(1-6) 2023.07

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  00319007

    　View Summary

    We develop an approach to chiral kinetic theories for electrons close to equilibrium and neutrinos away from equilibrium based on a systematic power counting scheme for different timescales of electromagnetic and weak interactions. Under this framework, we derive electric and energy currents along magnetic fields induced by neutrino radiation in general nonequilibrium states. This may be regarded as an effective chiral magnetic effect (CME), which is present without a chiral chemical potential, unlike the conventional CME. We also consider the so-called gain region of core-collapse supernovae as an example and find that the effective CME enhanced by persistent neutrino emission in time is sufficiently large to lead to the inverse cascade of magnetic and fluid kinetic energies and observed magnitudes of pulsar kicks. Our framework may also be applicable to other dense-matter systems involving nonequilibrium neutrinos.

  • Chiral effects in astrophysics and cosmology

    Kohei Kamada, Naoki Yamamoto, Di-Lun Yang

    Progress in Particle and Nuclear Physics 129   104016 2023.03

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  01466410

    　View Summary

    The microscopic quantum nature of elementary particles, chirality, leads to macroscopic phenomena like the chiral anomaly, chiral magnetic effect, and chiral plasma instability. We review recent progress of the studies of these chiral effects in high-energy astrophysics, such as pulsar kicks, magnetars, and core-collapse supernovae, and early Universe cosmology, such as the primordial magnetic field, baryogenesis, and chiral gravitational waves. We also provide a pedagogical introduction to the chiral effects and low-energy effective theories to describe them in and out of equilibrium—the chiral (magneto)hydrodynamics, chiral kinetic theory, and chiral radiation transport theory for neutrinos.

  • Unstable Nambu-Goldstone modes

    Naoki Yamamoto, Ryo Yokokura

    Physical Review D 106 （ 10 ） 105004(1-9) 2022.11

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  24700010

    　View Summary

    Nambu-Goldstone (NG) modes for 0-form and higher-form symmetries can become unstable in the presence of background fields. Examples include the instability of a photon with a time-dependent axion background or with a chirality imbalance, known as the chiral plasma instability, and the instability of a dynamical axion with a background electric field. We show that all these phenomena can be universally described by a symmetry algebra for 0-form and higher-form symmetries. We prove a counting rule for the number of unstable NG modes in terms of correlation functions of broken symmetry generators. Based on our unified description, we further give a simple new example where one of the NG modes associated with the spontaneous 0-form symmetry breaking U(1)×U(1)→{1} becomes unstable.

  • Chiral gravitational waves from thermalized neutrinos in the early Universe

    Philipp Gubler, Naoki Yamamoto, Di-Lun Yang

    Journal of Cosmology and Astroparticle Physics 09 （ 025 ） 1 - 36 2022.09

    Research paper (scientific journal), Joint Work, Accepted

    　View Summary

    We investigate polarized gravitational waves generated by chiral fermions in the early Universe. In particular, we focus on the contribution from left-handed neutrinos in thermal equilibrium with finite temperature and chemical potential in the radiation dominated era. We compute the correlation functions of gravitational fields pertinent to the Stokes parameter V characterizing the circular polarization of gravitational waves in the Minkowski and expanding spacetime backgrounds. In the expanding universe, we find that the thermalized neutrinos induce a non-vanishing V linear to the neutrino degeneracy parameter and wavenumber of gravitational waves in the long wavelength region. While the magnitude of the gravitational waves generated by thermal neutrinos is too small to be detectable by current and planned third generation gravitational wave detectors, their observations by future generation detectors for ultra-high frequency regimes could provide information on the neutrino degeneracy parameter in the early Universe.

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Papers, etc., Registered in KOARA 【 Display / hide 】

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Reviews, Commentaries, etc. 【 Display / hide 】

  • Crossover Between Quark Nuclear Matter and Condensed-Matter Physics

    Tomáš Brauner, Naoki Yamamoto

    Handbook of Nuclear Physics (Springer)     1 - 25 2022.07

    Article, review, commentary, editorial, etc. (scientific journal), Joint Work

  • カイラリティと宇宙

    山本 直希

    数理科学（特集：カイラリティとは何か） 59 ( 3 ) 45 - 51 2021.03

    Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media), Single Work

  • トポロジカル輸送現象入門

    山本 直希

    原子核研究 64   22 - 29 2020.02

    Article, review, commentary, editorial, etc. (scientific journal)

  • Chiral Transport Phenomena

    山本 直希

    原子核研究 63 ( 2 ) 72 - 73 2019.03

    Article, review, commentary, editorial, etc. (scientific journal), Single Work

  • 相対論的流体力学

    山本 直希

    数理科学（特集：相対論的思考法のすすめ） 55 ( 8 ) 36 - 42 2017.08

    Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media), Single Work

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Presentations 【 Display / hide 】

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

  • 素粒子論に基づく超新星のカイラル輻射流体力学の構築

    2019.04
    -
    2022.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Principal investigator

  • カイラル輸送現象による超新星爆発・初期宇宙の新物理

    2016.04
    -
    2019.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Young Scientists (B), Principal investigator

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Works 【 Display / hide 】

  • 他大学セミナー招待講演（東京工業大学 宇宙論研究室）

    山本 直希

    東京工業大学, 

    2022.07
    , 

    Other

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    Gravitational Spin Hall Effect

  • 他研究所セミナー招待講演（高エネルギー加速器研究機構）

    山本 直希

    オンライン, 

    2020.07
    , 

    Other

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    Magnetic monopoles and fermion number violation in chiral matter

  • 他研究所セミナー招待講演（高エネルギー加速器研究機構）

    山本 直希

    高エネルギー加速器研究機構, 

    2019.06
    , 

    Other

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    Chiral Soliton Lattice in QCD

  • 他大学セミナー招待講演（早稲田大学 天体物理学研究室）

    早稲田大学 天体物理学研究室, 

    2018.07
    , 

    Other

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    Chirality and Astrophysics

  • 他大学セミナー招待講演（東京大学 駒場キャンパス 素粒子論研究室）

    東京大学 駒場キャンパス 素粒子論研究室, 

    2017.12
    , 

    Other

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    カイラル輸送現象：ニュートリノから超新星爆発へ

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Awards 【 Display / hide 】

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Courses Taught 【 Display / hide 】

  • GRADUATE RESEARCH ON FUNDAMENTAL SCIENCE AND TECHNOLOGY 2

    2023

  • GRADUATE RESEARCH ON FUNDAMENTAL SCIENCE AND TECHNOLOGY 1

    2023

  • BACHELOR'S THESIS

    2023

  • INDEPENDENT STUDY ON FUNDAMENTAL SCIENCE AND TECHNOLOGY

    2023

  • QUARK-HADRON PHYSICS

    2023

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Social Activities 【 Display / hide 】

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Memberships in Academic Societies 【 Display / hide 】

  • 日本物理学会, 

    2006.09
    -
    Present
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