Current Affiliation Organization 【 display / non-display 】

Current Affiliation Organization 【 display / non-display 】

External Career 【 display / non-display 】

External Career 【 display / non-display 】

Published Papers 【 display / non-display 】

Published Papers 【 display / non-display 】

• Theoretical analysis of the maximum range of a projectile released from a pendulum

  Ken Yamamoto

  European Physical Journal Plus ( Springer Nature )  141   944   2026.08 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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    DOI

• Pólya urn model for analysis of football passes

  Ken Yamamoto

  Physical Review E ( American Physical Society )  112 ( 6 ) L062303   2025.12 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Geometric Brownian motion with random observation time as generalization of the double Pareto distribution

  Ken Yamamoto, Takashi Bando, Hirokazu Yanagawa, Yoshihiro Yamazaki

  Journal of Mathematical Physics ( American Institute of Physics )  66 ( 12 ) 123302   2025.12 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• On exceptionality of dimension three in terms of lattice angles

  Ken Yamamoto

  International Journal of Number Theory ( World Scientific )  21 ( 01 ) 113 - 132   2025.01 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  We investigate the lattice angle, namely, angles between two vectors with integer coordinates. We focus on the set of angles between a fixed integer vector and other integer vectors. For non-three-dimensional lattices, we proved that this set contains all lattice angles, irrespective of the fixed vector choice. In contrast, for the three-dimensional lattice, we proved that this set of angles cannot cover all lattice angles, for any fixed vector. Thus, only the three-dimensional lattice is an exception. We further provide the condition for a given three-dimensional integer vector to intersect another integer vector at a given angle, which involves a number-theoretic property of the squared norm of the given vector and the squared tangent of the given angle.

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• Exact solution of the propagation of ON-OFF signals by dispersive waves

  Ken Yamamoto

  Physica Scripta ( IOP Publishing )  99 ( 6 ) 065234 - 065234   2024.05 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Abstract The propagation of ON-OFF signals with dispersive waves is examined in this study. An integral-form exact solution for a simple ON-OFF switching event is derived, which holds for any dispersion relation. The integral can be exactly calculated for two types of dispersion relations. Further, the analysis of these solutions shows that the ON-OFF signal propagates with the group velocity and that the boundary thickness of the signal increases with time, typically at a rate proportional to the square root of time, owing to dispersion. Additionally, an approximate solution for a general dispersion relation is derived, and for a higher-complexity ON-OFF switching pattern is constructed.

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Other Papers 【 display / non-display 】

Other Papers 【 display / non-display 】

• A Network Science Approach to Team Sports

  Takuma Narizuka, Ken Yamamoto, Genki Ichinose

  Journal of the Japanese Society for Artificial Intelligence ( The Japanese Society for Artificial Intelligence )  40 ( 1 ) 12 - 19   2025.01  [Refereed]

   

  DOI

• 19pCW-8 Phase diagram of collective motions for bacterial cells in a shallow circular pool

  Jun-ichi Wakita, Shota Tsukamoto, Ken Yamamoto, Makoto Katori

  Meeting abstracts of the Physical Society of Japan   70   2867 - 2867   2015.08

   

  DOI

Presentations 【 display / non-display 】

Presentations 【 display / non-display 】

• Tracking data analysis for ball possession time in football matches

  Ken Yamamoto, Seiya Uezu, Keiichiro Kagawa, Yoshihiro Yamazaki, Takuma Narizuka

  10th International Congress on Industrial and Applied Mathematics  2023.08  -  2023.08 

Grant-in-Aid for Scientific Research 【 display / non-display 】

Grant-in-Aid for Scientific Research 【 display / non-display 】

• Grant-in-Aid for Scientific Research(C)

  Project Year: 2023.04  -  2026.03 

  Direct: 1,400,000 (YEN)  Overheads: 1,820,000 (YEN)  Total: 420,000 (YEN)

• Analysis of long-tailed phenomena using solvable stochastic processes

  Grant-in-Aid for Young Scientists(B)

  Project Year: 2013.04  -  2017.03 

  Investigator(s): Yamamoto Ken 

  Direct: 1,400,000 (YEN)  Overheads: 1,820,000 (YEN)  Total: 420,000 (YEN)

  　View Summary

  In this research project, heavy-tailed probability distributions in social and biological phenomena have been analyzed theoretically. First, a simple stochastic model has been constructed and analyzed, which is regarded as a model for the box-office grosse of a movie. This model can explain a power-law decay in the distribution of box-office grosses. Second, we have found that the number of articles within a law follows a lognormal distribution. The tree structure whose depth is normally distributed is an appropriate model for this lognormal behavior. Third, the size distribution of bacterial cells is studied. Our analysis of a phenomenological stochastic model for the bacterial growth has given a theoretical basis for the lognormality of the cell-size distribution.