Researcher basic information

• Doctor of Science, Hokkaido University, Sep. 2024

• https://researchmap.jp/skmsugawara?lang=en

• https://jglobal.jst.go.jp/detail?JGLOBAL_ID=202201010690644181
• https://orcid.org/0009-0004-4051-0598
• https://sites.google.com/view/sakumisugawara/

• https://orcid.org/0009-0004-4051-0598

• 202201010690644181

• 超平面配置
• トポロジー

• Natural Science, Geometry

• Bachelor's degree program, School of Science
• Master's degree program, Graduate School of Science
• Doctoral (PhD) degree program, Graduate School of Science

Research activity information

• Sep. 2025, 日本数学会, 2025年度日本数学会賞建部賢弘奨励賞
  超平面配置の研究：極小性，ハンドル分解，局所系コホモロジー
  菅原朔見
• Apr. 2022, Hokkaido University, The Excellent research award of the Graduate School of Science

• Even torsions in the homology group of the Milnor fiber boundary of hyperplane arrangements in $\mathbb{C}^3$
  Sakumi Sugawara
  01 Dec. 2025
  We study the homology group of the Milnor fiber boundary of a hyperplane arrangement in $\mathbb{C}^{3}$. By the work of Némethi--Szilárd, the homeomorphism type of the Milnor fiber boundary is combinatorially determined, and an explicit formula for the first Betti number is known. However, the torsion part of the first homology group is poorly understood. In this paper, under some conditions, we prove that the number of even-order torsion summands of the first homology group is greater than or equal to the Euler characteristic of the projectivized complement.
• First homology groups of the Milnor fiber boundary for generic hyperplane arrangements in C3$\mathbb {C}^{3}$
  Sakumi Sugawara
  Bulletin of the London Mathematical Society, Dec. 2025, [Peer-reviewed]
  Scientific journal, We study the Milnor fiber boundary for hyperplane arrangements in
  $\mathbb{C}^3$. This is one of the examples of non-isolated surface
  singularities, which are studied by N\'emethi--Szil\'ard. In this paper, we
  compute the first homology group of the Milnor fiber boundary for a generic
  arrangement and prove it is combinatorially determined. In particular, this
  gives the affirmative answer to the conjecture of Suciu.
• The cohomology ring of the boundary manifold of a combinatorial line arrangement
  Sakumi Sugawara
  09 Jul. 2025
  Cohen--Suciu proved that the cohomology ring of the boundary manifold of a
  complex projective line arrangement is isomorphic to the double of the
  cohomology ring of the complement. In this paper, we generalize this result to
  arbitrary combinatorial line arrangements, including non-realizable ones. The
  notion of the boundary manifold for combinatorial line arrangements was
  introduced by Ruberman--Starkston. To handle arbitrary combinatorial line
  arrangements, we construct explicit homology cycles following the method by
  Doig--Horn. Using these cycles, we compute the cohomology ring of the boundary
  manifold and prove that it is isomorphic to the double of the Orlik-Solomon
  algebra. As an application, we derive several results on the resonance variety
  of the boundary manifold.
• Divides with cusps and symmetric links
  Sakumi Sugawara
  Topology and its Applications, Mar. 2025, [Peer-reviewed]
  Scientific journal, A Divide with cusps is the image of a proper generic immersion from finite
  intervals and circles into a $2$-disk which allows to have cusps. A divide with
  cusps is the generalization of the notion of the divide which is introduced by
  A'Campo. From a divide with cusps, we can define the associated link in $S^3$.
  In this paper, we give the characterization of the link in $S^3$ which can be
  described as the associated link of a divide with cusps. In particular, we
  prove that every strongly invertible link and $2$-periodic link can be
  described as the link of a divide with cusps.
• Homogeneous quandles with abelian inner automorphism groups
  Takuya Saito; Sakumi Sugawara
  Journal of Algebra, 663, 150, 170, Elsevier BV, Feb. 2025, [Peer-reviewed]
  Scientific journal
• Betti numbers and torsions in homology groups of double coverings
  Suguru Ishibashi; Sakumi Sugawara; Masahiko Yoshinaga
  Advances in Applied Mathematics, 162, 102790, 102790, Elsevier BV, Jan. 2025, [Peer-reviewed]
  Scientific journal
• Handle decompositions and Kirby diagrams for the complement of plane algebraic curves
  Sakumi Sugawara
  18 Jun. 2023
  The complement of plane algebraic curves are well studied from topological
  and algebro-geometric viewpoints. In this paper, we will describe the explicit
  handle decompositions and the Kirby diagrams for the complement of plane
  algebraic curves. The method is based on the notion of braid monodromy. We
  refined this technique to obtain handle decompositions and Kirby diagrams.
• ℤ-local system cohomology of hyperplane arrangements and a Cohen–Dimca–Orlik type theorem
  Sakumi Sugawara
  International Journal of Mathematics, 34, 08, World Scientific Pub Co Pte Ltd, 15 Jun. 2023, [Peer-reviewed]
  Scientific journal, Local system cohomology groups of the complements of hyperplane arrangements have played an important role in the theory of hypergeometric integrals, the topology of Milnor fibers and covering spaces. One of the important theorems is the vanishing theorem for generic [Formula: see text]-local systems which goes back to Aomoto’s work. Later, Cohen, Dimca, and Orlik proved a stronger version of the vanishing theorem. In this paper, we prove a Cohen–Dimca–Orlik type theorem for [Formula: see text]-local systems.
• Divides with cusps and Kirby diagrams for line arrangements
  Sakumi Sugawara; Masahiko Yoshinaga
  Topology and its Applications, 313, 107989, 107989, Elsevier BV, May 2022, [Peer-reviewed]
  Scientific journal

• 平面曲線補集合のトポロジー
  菅原朔見, 第71回トポロジーシンポジウム講演集, Aug. 2024
• カスプ付きディバイドと対称的な結び目
  菅原朔見, 結び目の数理VI 報告集, 200, 207, Jan. 2024
• 超平面配置の二重被覆と整係数の局所系係数コホモロジー
  菅原朔見, 北海道大学数学講究録, 184, 559, 568, Mar. 2023
• 超平面配置の極小セル分割とカスプ付きディバイドによるKirby図式
  菅原朔見, 北海道大学数学講究録, 182, 223, 232, Mar. 2022
• カスプ付きディバイドから定まる絡み目と直線配置のKirby図式
  菅原朔見, 結び目の数理IV 報告集, 281, 293, Dec. 2021

• 超平面配置のトポロジー：組合せ的記述と一般化
  菅原朔見
  第9回数理新人セミナー, 18 Feb. 2026
  [Invited]
• Hyperplane arrangements and related 3-manifolds
  Sakumi Sugawara
  Arrangements in Osaka 2025, 15 Dec. 2025
• 超平面配置の特性多項式と曲がった直線への一般化
  菅原朔見
  佐世保高専数学セミナー, 05 Dec. 2025
  [Invited]
• 直線配置の境界多様体とその組合せ的一般化
  菅原朔見
  大阪大学トポロジーセミナー, 12 Nov. 2025
  [Invited]
• 超平面配置のミルナーファイバーとその境界
  菅原朔見
  特異点論若手勉強会2025, 05 Nov. 2025
  [Invited]
• Topology of hyperplane arrangements and related 3-manifolds
  菅原朔見
  トポロジー火曜セミナー, 07 Oct. 2025
  [Invited]
• 組合せ的直線配置から定まる3次元多様体のコホモロジー環について
  菅原朔見
  日本数学会2025年度秋季総合分科会, 19 Sep. 2025
• The intersection product on the boundary manifold of a combinatorial line arrangement
  Sakumi Sugawara
  Workshop and Summer school of hyperplane arrangements and related topics, 13 Aug. 2025
  [Invited]
• The cohomology ring of the boundary manifold of a combinatorial line arrangement
  菅原朔見
  Arrangement Days in NITech 2025, 12 Jun. 2025
  [Invited]
• 超平面配置の被覆空間とMilnorファイバー境界
  菅原朔見
  北海道大学数学教室談話会, 29 May 2025
  [Invited]
• 組合せ的直線配置から定まる3次元多様体について
  菅原朔見
  幾何学コロキウム（北海道大学）, 16 May 2025
  [Invited]
• Milnor fiber boundary of arrangements in \mathbb{C}^3
  菅原朔見
  Arrangement Days in Osaka, 24 Mar. 2025
  [Invited]
• 代数曲線補集合のハンドル分解
  菅原朔見
  第21回数学総合若手研究集会, 06 Mar. 2025
• Milnor fiber boundary for hyperplane arrangements
  菅原朔見
  接触構造、特異点、微分方程式及びその周辺, 21 Jan. 2025
  [Invited]
• Describe diffeomorphism type of plane curve complements via braid monodromy
  菅原朔見
  第9回代数幾何学研究集会 -宇部-, 11 Jan. 2025
  [Invited]
• 超平面配置の組合せ論とトポロジー
  菅原朔見
  北海道大学マトロイドセミナー, 12 Nov. 2024
  [Invited]
• Milnor fiber boudnary for hyperplane arrangements
  菅原朔見
  トポロジーとコンピュータ2024, 18 Sep. 2024
  [Invited]
• First homology groups of the Milnor fiber boundary for generic arrangements in \mathbb{C}^3
  菅原朔見
  2024年度日本数学会秋季総合分科会, 05 Sep. 2024
• 平面代数曲線補集合のトポロジー
  菅原朔見
  第71回トポロジーシンポジウム, 07 Aug. 2024
  [Invited]
• Milnor fiber boundary of hyperplane arrangements
  菅原朔見
  特異点論及びその周辺, 20 Jun. 2024
• Covering spaces and Milnor fiber boundary of hyperplane arrangements
  菅原朔見
  大阪大学トポロジーセミナー, 29 May 2024
  [Invited]
• Handle decompositions and Kirby diagrams for the complement of plane algebraic curves
  菅原朔見
  接触構造，特異点，微分方程式とその周辺, 18 Jan. 2024
• Divides with cusps and symmetric links
  Sakumi Sugawara
  結び目の数理Ⅵ, 24 Dec. 2023
• Description of Kirby diagrams for plane curve complements via braidmonodromy
  Sakumi Sugawara
  Hyperplane Arrangements 2023, 11 Dec. 2023
  [Invited]
• Handle decompositions and Kirby diagrams for the complement of plane algebraic curves d
  Sakumi Sugawara
  4-dimensional Topology, 11 Nov. 2023
• Handle decompositions and Kirby diagrams for the complement of plane algebraic curves
  Sakumi Sugawara
  日本数学会2023年度秋季総合分科会, 22 Sep. 2023
• Divides with cusps and symmetric links
  Sakumi Sugawara
  JV2023 Quy Nhon Workshop "Topology of Singularities and Related Topics", 15 Sep. 2023
  [Invited]
• Kirby diagrams for the complement of plane algebraic curves
  Sakumi Sugawara
  特異点論及びその周辺分野の深化と異分野への応用, 24 Jun. 2023
• Double coverings and integral local system cohomology of hyperplane arrangements
  Sakumi Sugawara
  第19回数学総合若手研究集会, 06 Mar. 2023
• Double coverings and integral local system cohomology of hyperplane arrangements
  Sakumi Sugawara
  Geometry and Topology Seminar, Hanoi Institute of Mathematics, 16 Feb. 2023
  [Invited]
• Double coverings and integral local system cohomology of arrangements
  Sakumi Sugawara
  Combinatorics, geometry, and commutative algebra of hyperplane arrangements, 16 Jan. 2023
  [Invited]
• Double coverings and integral local system cohomology of arrangements
  Sakumi Sugawara
  Singularities, arrangements, and low-dim. topology Ⅱ, 26 Nov. 2022
  [Invited]
• $\mathbb{Z}$-local system homology for hyperplane arrangements and a CDO type theorem
  Sakumi Sugawara
  日本数学会2022年度秋季総合分科会, 13 Sep. 2022
• Cohen--Dimca--Orlik type theorem for integral local systems
  Sakumi Sugawara
  第25回代数曲面ワークショップ at 南大沢, 19 Aug. 2022
  [Invited]
• Divides with cusps and Kirby diagrams for line arrangements
  Sakumi Sugawara
  Branched coverings, Degenerations, and Related Topics 2022, 07 Mar. 2022
  [Invited]
• Minimal cell decomposition for hyperplane arrangements and Kirby diagrams described by divides with cusps
  Sakumi Sugawara
  第18回数学総合若手研究集会〜数学の交叉点〜, 01 Mar. 2022
• $\mathbb{Z}$-local system homology for hyperplane arrangements
  Sakumi Sugawara
  超平面配置の数学とその進展2022, 15 Feb. 2022
• Links of divides with cusps and Kirby diagrams for line arrangements
  Sakumi Sugawara
  第5回数理新人セミナー, 10 Feb. 2022
• Links of divides with cusps and Kirby diagrams for line arrangements
  Sakumi Sugawara
  結び目の数理Ⅳ, 26 Dec. 2021
• Divides with cusps and Kirby diagrams for line arrangements
  Sakumi Sugawara
  広島大学トポロジーセミナー, 26 Oct. 2021
  [Invited]
• Divides with cusps and Kirby diagrams for line arrangements
  菅原朔見
  日本数学会2021年度秋季総合分科会, 16 Sep. 2021
• Divides with cusps and Kirby diagrams for line arrangements
  菅原朔見
  大阪大学トポロジーセミナー, 14 Jul. 2021
  [Invited]
• Divides with cusps and Kirby diagrams for line arrangements
  菅原朔見
  特異点の未来, 24 Jun. 2021
• Handle decomposition of line arrangements
  Sakumi Sugawara
  Recent developments in Arrangements, 15 Feb. 2021
• Handle decomposition of line arrangements
  菅原朔見
  第4回数理新人セミナー, 11 Feb. 2021

• 日本数学会

• 超平面配置の被覆空間、Milnorファイバー及びその境界の位相的研究
  科学研究費助成事業
  Jul. 2025 - Mar. 2027
  菅原 朔見
  日本学術振興会, 研究活動スタート支援, 北海道大学, 25K23326
• カスプ付きdivideを用いた直線配置の低次元トポロジー的研究
  科学研究費助成事業 特別研究員奨励費
  22 Apr. 2022 - 31 Mar. 2025
  菅原 朔見
  日本学術振興会, 特別研究員奨励費, 北海道大学, 22J20470

• 多項式を使って数えよう
  07 Jun. 2025 - 07 Jun. 2025
  Lecturer
  第133回数学教育実践研究会