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math.CO2025
Comparing classes of highly symmetric graphs: From -arc-transitive to -distance-transitive
Wei Jin, Jack H. Koolen, Chenhui Lv
A -distance-transitive graph is a vertex-transitive graph whose vertex stabilizer is transitive on both the first- and second-step neighborhoods. This concept simultaneously gen…
math.CO2025
An improved bound for strongly regular graphs with smallest eigenvalue
Jack Koolen, Chenhui Lv, Greg Markowsky +1
In 1979, Neumaier gave a bound on in terms of and , where is the smallest eigenvalue of a primitive strongly regular graph, unless the graph in question belongs to…
math.CO2025
A Bose-Laskar-Hoffman theory for -bounded graphs with fixed smallest eigenvalue
Jack H. Koolen, Hong-Jun Ge, Chenhui Lv +1
In 2018, by Ramsey and Hoffman theory, Koolen, Yang, and Yang presented a structural result on graphs with smallest eigenvalue at least and large minimum degree. In this study…