Mitsugu Hirasaka

activity

20122021

collaborators

4 papers

math.CO2021

Association schemes with a certain type of $p$ -subschemes

Wasim Abbas, Mitsugu Hirasaka

In this article, we focus on association schemes with some properties derived from the orbitals of a transitive permutation group $G$ with a one-point stabilizer $H$ satisfying $H…

math.CO2016

The number of ideals of $Z [x]$ containing $x (x - α) (x - β)$ with given index

Mitsugu Hirasaka, Semin Oh

It is well-known that a connected regular graph is strongly-regular if and only if its adjacency matrix has exactly three eigenvalues. Let $B$ denote an integral square matrix and…

math.CO2014

Isomorphism classes of association schemes induced by Hadamard matrices

Mitsugu Hirasaka, Kijung Kim, Hyonju Yu

Every Hadamard matrix $H$ of order $n > 1$ induces a graph with $4 n$ vertices, called the Hadamard graph $Γ (H)$ of $H$ . Since $Γ (H)$ is a distance-regular graph with diameter $4$ ,…

math.CO2012

On $p$ -schemes of order $p^{3}$

Jung Rae Cho, Mitsugu Hirasaka, Kijung Kim

Let $(X, S)$ be a $p$ -scheme of order $p^{3}$ and $T$ the thin residue of $S$ . Now we assume that $T$ has valency $p^{2}$ . It is easy to see that one of the following holds: (i) $|T|=p^…

Association schemes with a certain type of p-subschemes

The number of ideals of Z[x] containing x(x−α)(x−β) with given index

Isomorphism classes of association schemes induced by Hadamard matrices

On p-schemes of order p3

Association schemes with a certain type of $p$ -subschemes

The number of ideals of $Z [x]$ containing $x (x - α) (x - β)$ with given index

On $p$ -schemes of order $p^{3}$