Performance information

• Comparison of gap-based and flow-based control strategies using a new controlled stochastic cellular automaton model for traffic flow
  Kayo Kinjo; Akiyasu Tomoeda
  Transportation Letters, First page：1, Last page：11, Oct. 2024, [Reviewed], [Lead]
  Informa UK Limited, Scientific journal
  DOI：https://doi.org/10.1080/19427867.2024.2417150
  DOI ID：10.1080/19427867.2024.2417150, ISSN：1942-7867, eISSN：1942-7875
• Improvement of System Identification of Stochastic Systems via Koopman Generator and Locally Weighted Expectation
  Yuki Tahara; Kakutaro Fukushi; Shunta Takahashi; Kayo Kinjo; Jun Ohkubo
  Journal of the Physical Society of Japan, Volume：93, Number：7, First page：074006-1, Last page：074006-9, Jul. 2024, [Reviewed]
  Physical Society of Japan, Scientific journal
  DOI：https://doi.org/10.7566/jpsj.93.074006
  DOI ID：10.7566/jpsj.93.074006, ISSN：0031-9015, eISSN：1347-4073
• Extraction of nonlinearity in neural networks with Koopman operator
  Naoki Sugishita; Kayo Kinjo; Jun Ohkubo
  Journal of Statistical Mechanics: Theory and Experiment, Volume：2024, Number：7, First page：073401, Last page：073401, Jul. 2024, [Reviewed]
  Abstract
  
  Nonlinearity plays a crucial role in deep neural networks. In this paper, we investigate the degree to which the nonlinearity of the neural network is essential. For this purpose, we employ the Koopman operator, extended dynamic mode decomposition, and the tensor-train format. The Koopman operator approach has been recently developed in physics and nonlinear sciences; the Koopman operator deals with the time evolution in the observable space instead of the state space. Since we can replace the nonlinearity in the state space with the linearity in the observable space, it is a hopeful candidate for understanding complex behavior in nonlinear systems. Here, we analyze learned neural networks for the classification problems. As a result, the replacement of the nonlinear middle layers with the Koopman matrix yields enough accuracy in numerical experiments. In addition, we confirm that the pruning of the Koopman matrix gives sufficient accuracy even at high compression ratios. These results indicate the possibility of extracting some features in the neural networks with the Koopman operator approach.
  IOP Publishing, Scientific journal
  DOI：https://doi.org/10.1088/1742-5468/ad5713
  DOI ID：10.1088/1742-5468/ad5713, eISSN：1742-5468
• Dynamics of quantum double dark-solitons and an exact finite-size scaling of Bose–Einstein condensation
  Kayo Kinjo; Jun Sato; Tetsuo Deguchi
  Journal of Physics A: Mathematical and Theoretical, Volume：56, Number：16, First page：164001, Last page：164001, Mar. 2023, [Reviewed], [Lead]
  Abstract
  
  We show several novel aspects in the exact non-equilibrium dynamics of quantum double dark-soliton states in the Lieb–Liniger model for the one-dimensional Bose gas with repulsive interactions. We also show an exact finite-size scaling of the fraction of the quasi-Bose–Einstein condensation (BEC) in the ground state, which should characterize the quasi-BEC in quantum double dark-soliton states that we assume to occur in the weak coupling regime. First, we show the exact time evolution of the density profile in the quantum state associated with a quantum double dark-soliton by the Bethe ansatz. Secondly, we derive a kind of macroscopic quantum wave-function effectively by exactly evaluating the square amplitude and phase profiles of the matrix element of the field operator between the quantum double dark-soliton states. The profiles are close to those of dark-solitons particularly in the weak-coupling regime. Then, the scattering of two notches in the quantum double dark-soliton state is exactly demonstrated. It is suggested from the above observations that the quasi-BEC should play a significant role in the dynamics of quantum double dark-soliton states. If the condensate fraction is close to 1, the quantum state should be well approximated by the quasi-BEC state where the mean-field picture is valid.
  IOP Publishing, Scientific journal
  DOI：https://doi.org/10.1088/1751-8121/acc496
  DOI ID：10.1088/1751-8121/acc496, ISSN：1751-8113, eISSN：1751-8121
• Quantum Dark Solitons in the 1D Bose Gas: From Single to Double Dark-Solitons
  Kayo Kinjo; Eriko Kaminishi; Takashi Mori; Jun Sato; Rina Kanamoto; Tetsuo Deguchi
  Universe, Volume：8, Number：1, First page：2, Last page：2, Dec. 2021, [Reviewed], [Lead]
  We study quantum double dark-solitons, which give pairs of notches in the density profiles, by constructing corresponding quantum states in the Lieb–Liniger model for the one-dimensional Bose gas. Here, we expect that the Gross–Pitaevskii (GP) equation should play a central role in the long distance mean-field behavior of the 1D Bose gas. We first introduce novel quantum states of a single dark soliton with a nonzero winding number. We show them by exactly evaluating not only the density profile but also the profiles of the square amplitude and phase of the matrix element of the field operator between the N-particle and (N−1)-particle states. For elliptic double dark-solitons, the density and phase profiles of the corresponding states almost perfectly agree with those of the classical solutions, respectively, in the weak coupling regime. We then show that the scheme of the mean-field product state is quite effective for the quantum states of double dark solitons. Assigning the ideal Gaussian weights to a sum of the excited states with two particle-hole excitations, we obtain double dark-solitons of distinct narrow notches with different depths. We suggest that the mean-field product state should be well approximated by the ideal Gaussian weighted sum of the low excited states with a pair of particle-hole excitations. The results of double dark-solitons should be fundamental and useful for constructing quantum multiple dark-solitons.
  MDPI AG, Scientific journal
  DOI：https://doi.org/10.3390/universe8010002
  DOI ID：10.3390/universe8010002, eISSN：2218-1997

• Sep. 2020 - Present, The Japan Society for Industrial and Applied Mathematics
• Mar. 2018 - Present

• 研究会「第5回首都圏素粒子論研究室合同研究発表会」運営・幹事代表　　　　　　　　　　　　　　　
  Planning etc
  12 Mar. 2017 - 14 Mar. 2017
  Academic society etc

• 第587回埼玉新聞「サイ・テクこらむ」への寄稿　　　　　　　　　　　　　　　
  contribution
  埼玉新聞社, 埼玉新聞, 04 Dec. 2024 - 04 Dec. 2024

• YouTube動画「数理モデルでシミュレーション」に出演　　　　　　　　　　　　　　　
  Jan. 2025, [Internet]
  「理工系の研究者紹介・彩の国・理工系進路選択エンカレッジプログラム（JST女子中高生プログラム）」の一環で、女子中高生に理系科目に対して親近感を持ってもらうために、埼玉大学の理工系女性教員の研究やその人の人柄を紹介する動画に出演しました。