Butsuri
Online ISSN : 2423-8872
Print ISSN : 0029-0181
ISSN-L : 0029-0181
Volume 74 , Issue 8
Showing 1-23 articles out of 23 articles from the selected issue
Preface
Contents
Topics
Artificial Intelligence and Physics
  • Hideyuki Nakashima
    Type: Artificial Intelligence and Physics
    2019 Volume 74 Issue 8 Pages 526-532
    Published: August 05, 2019
    Released: January 31, 2020
    JOURNALS RESTRICTED ACCESS

    When a complex system is decomposed into subsystems, it looses some of the essential property. In other words, the whole is not the sum of its parts. Therefore, the traditional divide and conquer method, which is a commonstrategy for natural sciences, is not applicable.

    Intelligence is a complex system. The world that an intelligent system handles is also a complex system. Analytical approach cannot be used to construct of control intelligent systems. We will review the history of AI research from the viewpoint of complex systems and propose a new constructive methodology. This methodology applies both to the research and the design of intelligent systems.

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Reviews
Researches
  • Shunichiro Kinoshita, Takahisa Igata
    Type: Researches
    2019 Volume 74 Issue 8 Pages 542-547
    Published: August 05, 2019
    Released: January 31, 2020
    JOURNALS RESTRICTED ACCESS

    The Blandford–Znajek process is an energy-extraction mechanism from a rotating black hole by force-free electromagnetic fields. Since this process can efficiently achieve powerful energy fluxes, it has been widely believed to be a viable mechanism for the formation of relativistic jets. From a spacetime perspective, the dynamics of magnetic field lines of force-free electromagnetic fields can be rewritten into a quite similar form for the dynamics of strings. Using this formalism, we explicitly show that the energy and angular-momentum fluxes for stationary and axisymmetric force-free electromagnetic fields have identical properties to those for rigidly rotating Nambu–Goto strings. Thus, we conclude that the Blandford–Znajek process is kinematically identical to an energy-extraction mechanism by the Nambu–Goto string and the magnetic field lines with magnetic tension play an important role in the Blandford–Znajek process.

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  • Minoru Tanaka, Noboru Sasao, Motohiko Yoshimura
    Type: Researches
    2019 Volume 74 Issue 8 Pages 548-553
    Published: August 05, 2019
    Released: January 31, 2020
    JOURNALS RESTRICTED ACCESS

    Radiative emission of neutrino pair (RENP) from a metastable excited state of an atom is supposed to be sensitive to neutrino properties such as absolute masses and Dirac-Majorana distinction. A rate enhancement mechanism using quantum coherence among atoms in a macroscopic target, macrocoherent amplification, is explained. The spectral rate of macrocoherently amplified RENP is theoretically evaluated in several setups. In addition, the results of experiments that exhibit the macrocoherent amplification in a two-photon QED process, paired superradiance (PSR), are also presented. We have observed an amplification of 1018 or larger in the PSR process of parahydrogen, which confirms the validity of the macrocoherent amplification.

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  • Taro Nakajima, Yusuke Tokunaga, Taka-hisa Arima
    Type: Researches
    2019 Volume 74 Issue 8 Pages 554-559
    Published: August 05, 2019
    Released: January 31, 2020
    JOURNALS RESTRICTED ACCESS

    Since the discovery of spontaneous electric polarization in TbMnO3 , it has been recognized that inversion symmetry breaking by magnetic order can lead to ferroelectricity. Here, we demonstrate that an application of uniaxial stress can be a useful tool to control the spin-driven ferroelectricity. We performed pyroelectric measurements on a tetragonal multiferroic Ba2CoGe2O7 , revealing that the application of uniaxial stress along the [110] direction can induce electric polarization of spin origin. We also found that DyFeO3 simultaneously exhibits both the ferromagnetic moment and electric polarization under uniaxial stress. Although, in general, an application of uniaxial stress cannot induce large atomic displacements, but it can change symmetry of matter, which is essential for cross-correlated phenomena in spin-driven multiferroics.

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