石塚 裕大
Yasuhiro Ishitsuka

Research Interest: 

• Diophantine geometry, arithmetic invariant theory and related topics.

• Algebraic combinatorics and related topics.

Attend:

• 2025.6.2-4: (Organize, Talk) Workshop on Number Theory and Integrable Systems, Kobe University.

Preprints :

• Exponential sums over singular binary quartic forms and applications.
  Y. Ishitsuka, T. Tanugichi, F. Thorne and S.-Y. Xiao, submitted. (arXiv)

• The integrality of algebraic Witt vectors over imaginary quadratic fields is decidable.
  Y. Ishitsuka, and T. Uramoto. submitted.

Papers : 

• On the ACC for lengths of extremal rays.
  O. Fujino and Y. Ishitsuka, Tohoku Math. J. 65 (2013), no.1, 93--103.

• An Algorithm to obtain linear determinantal representations of smooth plane cubics over finite fields.
  Y. Ishitsuka, JSIAM Lett. 8 (2016), 69--72.

• On the symmetric determinantal representations of the Fermat curves of prime degree.
  Y. Ishitsuka and T. Ito, Int. J. Number Theory 12 (2016), no.4, 955--967.

• The local-global principle for symmetric determinantal representationsof smooth plane curves.
  Y. Ishitsuka and T. Ito, Ramanujan J. 43 (2017), 141--162.

• The local-global principle for symmetric determinantal representationsof smooth plane curves in characteristic two.
  Y. Ishitsuka and T. Ito, J. Pure Appl. Algebra 221 (2017), 1316--1321.

• A positive proportion of cubic curves over Q admit linear determinantal representations.
  Y. Ishitsuka, J. Ramanujan Math. Soc. 32 (2017), 231--257.

• On algorithms to obtain linear determinantal representations of smooth plane curves of higher degree.
  Y. Ishitsuka, T. Ito and T. Ohshita, JSIAM Lett. 11 (2019), 9--12.

• Explicit calculation of the mod 4 Galois representations associated with the Fermat quartic.
  Y. Ishitsuka, T. Ito and T. Ohshita, Int. J. Number Theory 16 (2020), no.4, 881--905.

• The local-global property for bitangents of plane quartics.
  Y. Ishitsuka, T. Ito, T. Ohshita, T. Taniguchi and Y. Uchida, JSIAM Lett. 12 (2020), 9--12.

• Systematic clustering algorithm for chromatin accesibility data and its application to hematopoietic cells.
  A. Tanaka, Y. Ishitsuka, H. Ohta, A. Fujimoto, J-i. Yasunaga and M. Matsuoka.
  PLoS Comput. Biol. 30 Nov 2020; 16 (11): e1008422.

• The Hasse principle for finite Galois modules allowing exceptional sets of positive density.
  Y. Ishitsuka and T. Ito,  Int. J. Number Theory 18 (2022), no.9, 1895--1919.

• The modularity of elliptic curves over all but finitely many totally real fields of degree 5.
  Y. Ishitsuka, T. Ito and S. Yoshikawa, Res. Number Theory 8, 82 (2022).

• Emergent Centrality in rank-based supplanting process.
  K. Shimomura, Y. Ishitsuka and H. Ohta. Phys. Rev. E 107 (2023), 034114.

• Integrative analysis of ATAC-seq and RNA-seq for cells infected by human T-cell leukemia virus type 1.
  A. Tanaka, Y. Ishitsuka, H. Ohta, N. Takenouchi, M. Nakagawa, K.-R. Koh, C. Ohnishi, H. Tanaka, A. Fujimoto, J-i. Yasunaga and M. Matsuoka.
  PLoS Comput. Biol. 2 Jan/ 2025 21(1): e1012690. 

• On the proportions of soluble forms in some families of locally soluble binary quartic forms.
  Y. Ishitsuka and Y. Kanamura. Tokyo J. Math. 47(2), 505-521, December 2024.

• Periods modulo p of integer sequences associated with division polynomials of genus 2 curves.
  Y. Ishitsuka, T. Ito,  T. Ohshita, T. Taniguchi and Y. Uchida. New York J. Math. 31 (2025) 568–588.

Others: 

• On the integrality of algebraic Witt vectors over imaginary quadratic fields.
  Y. Ishitsuka and T. Uramoto, on Symbolic Computation for Software Science 2021.

Education:

• 2025.4-9.: Combinatorics @ Kyushu University.

• 2024.12-2025.3.: Complex Analysis @ Kyushu University.

• 2023.9-2024.3.: Complex Analysis @ Kyushu University.

• 2022.12-2023.3.: Complex Analysis @ Kyushu University.

• 2021.12-2022.3.: Complex Analysis @ Kyushu University.

• (Under construction)

Talks:

• 2024.7.15-19: Lightning talk at ANTS XVI at MIT.

• 2024.8.8: Talk at Gunma University (link in Japanese).

• 2024.8.26-30: Analytic Number Theory and Arithmetic Statistics, in Montreal.

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