3 papers
math.CO2018
Characterization of finite metric space by their isometric sequences
Mitsugu Hirasaka, Masashi Shinohara
Let be a finite metric space with . For a positive integer we define to be the quotient set of all -subsets of by isometry, and we denote $|A_k(X…
math.CO2018
Schurity and separability of quasiregular coherent configurations
Mitsugu Hirasaka, Kijung Kim, Ilia Ponomarenko
A permutation group is said to be quasiregular if every its transitive constituent is regular, and a quasiregular coherent configuration can be thought as a combinatorial analog of…
math.CO2017
New families of Hadamard matrices with maximum excess
Mitsugu Hirasaka, Koji Momihara, Sho Suda
In this paper, we find regular or biregular Hadamard matrices with maximum excess by negating some rows and columns of known Hadamard matrices obtained from quadratic residues of f…