Hadamard matrices : construction by groups and examples by computer
Project/Area Number  10640031 
Research Category 
GrantinAid for Scientific Research (C)

Allocation Type  Singleyear Grants 
Section  一般 
Research Field 
Algebra

Research Institution  Ehime University 
Principal Investigator 
NIWASAKI Takashi(1999) Ehime University, Mathematical Science, Assistant, 理学部, 助手 (50218252)
木村 浩 愛媛大, 理学部, 教授 (70023570)

CoInvestigator(Kenkyūbuntansha) 
SASAKI Hiroki Ehime University, Mathematical Science, Assoc. Prof., 理学部, 助教授 (60142684)
KISO Kazuhiro Ehime University, Mathematical Science, Assistant, 理学部, 教授 (60116928)
NOGURA Tsugunori Ehime University, Mathematical Science, Professor, 理学部, 教授 (00036419)
SHAKHMATOV Dmitri Ehime University, Mathematical Science, Assoc. Prof., 理学部, 助教授 (90253294)
HIRAIDE Koichi Ehime University, Mathematical Science, Assoc. Prof., 理学部, 助教授 (50181136)
宮本 雅彦 筑波大学, 数学系, 教授 (30125356)
大森 博之 愛媛大学, 教育学部, 教授 (20036370)
庭崎 隆 愛媛大学, 理学部, 助手 (50218252)

Project Period (FY) 
1998 – 1999

Project Status 
Completed(Fiscal Year 1999)

Budget Amount *help 
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1999 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1998 : ¥2,200,000 (Direct Cost : ¥2,200,000)

Keywords  Hadamard matrix / finite groups / dihedral groups / Hadamard conjecture / 二面体群 / コード / 2面体群 / デザイン 
Research Abstract 
Let G be a dihedral group of order 2n and let A,B, C and D be its subsets. Recently, H. Kimura introduced a method to construct a Hadamard matrix H (A, B, C, D) of degree 8n + 4 under certain conditions for these subsets. In this research, we studied some properties of these subsets in terms of the integral group ring ZG, and gave some examples for small odd integers n as follows : 1. We generalized this construction to arbitrary groups G of order 2n. 2. We gave some variants of this construction. 3. We considered several actions on G (and on its subsets) that preserve the conditions for A, B, C and D. The holomorph of G was included. 4. We studied two particular cases : (1) A, B, C and D are symmetric ; (2) more strongly, for a dihedral group G, they are yinvariant. In these cases, the conditions for A, B, C and D simplify to problems similar to that of four square sums in the group ring ZG. 5. By using computer, we constructed Hadamard matrices H (A, B, C, D) from dihedral groups for all odd integers n < 30 except for n = 15. It seems that Hadamard matrices coming from dihedral groups are not a few. Furthermore it is interesting to note that almost all examples are yinvariant type.

Report
(3results)
Research Output
(3results)