Aoki, Kenichiro



Faculty of Economics (Hiyoshi)



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Career 【 Display / hide

  • 1989.08

    Physics Department, UCLA,Research Associate

  • 1992.09

    UCLA物理学科 ,AdjunctAssociateProfessor

  • 1993.06

    Research Associate, Department of Physics, Tokyo Institute of Technology

  • 1995.04


  • 1999.04


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Academic Background 【 Display / hide

  • 1984.03

    The University of Tokyo, Faculty of Science

    University, Graduated

  • 1985.10

    Princeton University, Physics Department

    United States, Graduate School, Completed, Master's course

  • 1989.10

    Princeton University, Department of Physics

    United States, Graduate School, Completed, Doctoral course

Academic Degrees 【 Display / hide

  • Ph. D., Princeton University, Dissertation, 1989.10


Research Areas 【 Display / hide

  • Natural Science / Mathematical physics and fundamental theory of condensed matter physics (Physics of Non-equilibirum)

  • Natural Science / Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics (Particle theory, string theory)


Books 【 Display / hide

  • 現代物理学を学びたい人へ - 原子から宇宙まで -

    AOKI KENICHIRO, 慶應義塾大学出版会, 2011.05

  • 力学(コア・テキスト)

    Kenichiro Aoki, サイエンス社, 2011

  • 素粒子物理学

    原 康夫,稲見 武夫,青木 健一郎, 朝倉書店, 2000

Papers 【 Display / hide

  • Fluctuation spectroscopy of surface melting of ice with and without impurities

    Mitsui T., Aoki K.

    Physical Review E (Physical Review E)  99 ( 1 )  2019.01

    ISSN  24700045

     View Summary

    © 2019 American Physical Society. Water is ubiquitous, and the surface properties of ice have been studied for some time, due to their importance. A liquidlike layer (LLL) is known to exist on ice, below the melting point. We use surface thermal fluctuation spectroscopy to study the LLL, including its thickness, for pure ice, and for ice with impurities. We find that the properties of the LLL are experimentally those of liquid water, with thickness much smaller than previous results. We also find that impurities cause the LLL to be thicker, and quite inhomogeneous, with properties depending on the dopant.

  • Dynamically enhanced low-coherence interferometry

    Mitsui T., Aoki K.

    Review of Scientific Instruments (Review of Scientific Instruments)  89 ( 9 )  2018.09

    ISSN  00346748

     View Summary

    © 2018 Author(s). In the investigations of inhomogeneous media, availability of methods to study the interior of the material without affecting it is valuable. Optical coherence tomography provides such a functionality by providing depth resolved images of semi-transparent objects non-invasively. This is especially useful in medicine and is used not only in research but also in clinical practice. Optical coherence tomography characterizes each cross section by its reflectance. The basic physics principle underlying optical coherence tomography is low-coherence interferometry, which is combined with lateral scanning to produce cross sections. It is clearly desirable to obtain more detailed information regarding each cross section, if available. We have developed a system which measures the fluctuation spectra at all depths in low-coherence interferometry. By providing more information for each cross section, this can in principle be effective in tissue characterization and pathological diagnosis. The system uses the time dependence of the low-coherence interferometry data to obtain the fluctuation spectrum at each depth. Additionally, noise reduction is applied to obtain the spectra without unwanted noise, such as shot-noise, which can swamp the signal. The measurement system is applied to samples with no external stimuli, and depth resolved thermal fluctuation spectra of the samples are obtained. These spectra are compared with their corresponding theoretical expectations and are found to agree. The measurement system requires dualizing the detectors in the low-coherence interferometer but otherwise requires little additional equipment. The measurements were performed in ten to a hundred seconds.

  • Thermal interface fluctuations of liquids and viscoelastic materials

    Aoki K., Mitsui T.

    Progress of Theoretical and Experimental Physics (Progress of Theoretical and Experimental Physics)  2018 ( 4 )  2018.04

    ISSN  2050-3911

     View Summary

    © 2018 Physical Society of Japan. All rights reserved. Spectra of thermal fluctuations of a wide range of interfaces, from liquid/air, viscoelastic material/ air, liquid/liquid to liquid/viscoelastic material interfaces, were measured over a 100 Hz to 10MHz frequency range. The obtained spectra were compared with the fluctuation theory of interfaces, and found to be mostly in quite good agreement, when the theory was generalized to apply to thermal fluctuations of liquid/viscoelastic material interfaces. The loss modulus of viscoelastic materials has been incorporated into the theory, and its effects observed experimentally. The spectra were measured using a system that combines light reflection, statistical noise reduction through averaged correlations, and confocal microscopy. It requires only a small area of the interface (∼1μm2), relatively short times for measurements (≲ few min), and can also be applied to highly viscous materials.

  • Order and chaos in the one-dimensional ϕ<sup>4</sup> model: N-dependence and the Second Law of Thermodynamics

    Hoover W., Aoki K.

    Communications in Nonlinear Science and Numerical Simulation (Communications in Nonlinear Science and Numerical Simulation)  49   192 - 201 2017.08

    ISSN  10075704

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    © 2017 Elsevier B.V. We revisit the equilibrium one-dimensional ϕ4 model from the dynamical systems point of view. We find an infinite number of periodic orbits which are computationally stable. At the same time some of the orbits are found to exhibit positive Lyapunov exponents! The periodic orbits confine every particle in a periodic chain to trace out either the same or a mirror-image trajectory in its two-dimensional phase space. These “computationally stable” sets of pairs of single-particle orbits are either symmetric or antisymmetric to the very last computational bit. In such a periodic chain the odd-numbered and even-numbered particles’ coordinates and momenta are either identical or differ only in sign. “Positive Lyapunov exponents” can and do result if an infinitesimal perturbation breaking a perfect two-dimensional antisymmetry is introduced so that the motion expands into a four-dimensional phase space. In that extended space a positive exponent results. We formulate a standard initial condition for the investigation of the microcanonical chaotic number dependence of the model. We speculate on the uniqueness of the model's chaotic sea and on the connection of such collections of deterministic and time-reversible states to the Second Law of Thermodynamics.

  • Observation of reflectance fluctuations in metals

    Mitsui T., Aoki K.

    Physical Review A (Physical Review A)  95 ( 4 )  2017.04

    ISSN  24699926

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    © 2017 American Physical Society. Through the study of the power spectra of a monochromatic light beam reflected by metallic mirrors, fluctuations in their reflectance are observed. The power spectra were obtained down to a factor 10-6 below the standard quantum limit, with a dynamic range of 105 in frequency and power, using methods we developed. The properties of the spectra are investigated, and their dependence on the material is analyzed. The physics underlying the phenomenon is also discussed. These fluctuations provide a window into the degrees of freedom responsible for the reflection process in metals.

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

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Presentations 【 Display / hide

  • Observation of Spontaneous Quantum Fluctuations in Photon Absorption by Atoms

    Kenichiro Aoki, Takahisa Mitsui

    The 12th Asia Pacific Physics Conference of AAPPS (International Conference Halls, Makuhari Messe Chiba, Japan) , 


    Oral presentation (general), The Association of Asia Pacific Physical Societies (AAPPS)

  • Direct Observations of Surface Thermal Fluctuations Below Shot Noise Levels

    Kenichiro Aoki, Takahisa Mitsui

    The 12th Asia Pacific Physics Conference of AAPPS (International Conference Halls, Makuhari Messe Chiba, Japan) , 


    Poster presentation, The Association of Asia Pacific Physical Societies

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

  • 散射雑音を除去した光計測を基盤とする揺らぎのダイナミックスの研究


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

Works 【 Display / hide

  • 自然科学系を核とした教養教育の将来




    Other, Joint

  • 文化系学生が学ぶ物理学実験





Courses Taught 【 Display / hide











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