Da Zhao

activity

20172026

collaborators

Showing math.COShow all

10 papers · 1 filter

math.CO2026

On Neumaier Cayley graphs

Rhys J. Evans, Sergey Goryainov, Grigory Ryabov +1

In the present paper, we study Neumaier Cayley graphs. First, we give a criterion for a Cayley graph to be a Neumaier graph with a spread given by the cosets of a subgroup. Further…

math.CO2025

Generalized block diagonal Laplacian spectrum of graphs

Yanrui Xu, Da Zhao

We reduce the $p^{2}$ block all-one matrices in the generalized block Laplacian spectrum of graphs to $p$ block all-one matrices in the generalized block diagonal Lapalcian spectrum…

math.CO2024

Bivariate $Q$ -polynomial structures for the nonbinary Johnson scheme and the association scheme obtained from attenuated spaces

Eiichi Bannai, Hirotake Kurihara, Da Zhao +1

The study of $P$ -polynomial association schemes (distance-regular graphs) and $Q$ -polynomial association schemes, and in particular $P$ - and $Q$ -polynomial association schemes, has…

math.CO2023

Multivariate P- and/or Q-polynomial association schemes

Eiichi Bannai, Hirotake Kurihara, Da Zhao +1

The classification problem of $P$ - and $Q$ -polynomial association schemes has been one of the central problems in algebraic combinatorics. Generalizing the concept of $P$ - and $Q$ -…

math.CO2020

Classification of partially metric Q-polynomial association schemes with $m_{1} = 4$

Da Zhao

We classify the Q-polynomial association schemes with $m_{1} = 4$ which are partially metric with respect to the nearest neighbourhood relation. An association scheme is partially…

math.CO2020

Explicit construction of exact unitary designs

Eiichi Bannai, Yoshifumi Nakata, Takayuki Okuda +1

The purpose of this paper is to give explicit constructions of unitary $t$ -designs in the unitary group $U (d)$ for all $t$ and $d$ . It seems that the explicit constructions were so…