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20182026
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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.CO2026

Divisible design graphs from Higmanian association schemes

Grigory Ryabov

An imprimitive symmetric indecomposable association scheme of rank 5 is said to be Higmanian. A divisible design graph is a graph whose adjacency matrix is an incidence matrix of a…

math.CO2026

Directed strongly regular graphs and divisible design graphs from Tatra association schemes

Mikhail Muzychuk, Grigory Ryabov

In this paper, we construct directed strongly regular graphs and divisible design graphs with new parameters merging some basic relations of so-called Tatra associations schemes. W…

math.CO2025

Deza Cayley graphs from difference sets

Grigory Ryabov

In this note, we provide several constructions of Deza Cayley graphs over groups having a generalized dihedral subgroup. These constructions are based on a usage of (relative) diff…

math.CO2025

On CI-property of normal Cayley digraphs over abelian groups

Grigory Ryabov

A Cayley digraph over a finite group is said to be CI if for every Cayley digraph over isomorphic to , there is an isomorphism from to whic…

math.CO2024

On a family of divisible design digraphs

Mikhail Muzychuk, Grigory Ryabov

For every odd prime power , a family of pairwise nonisomorphic normal arc-transitive divisible design Cayley digraphs with isomorphic neighborhood designs over a Heisenberg grou…