engleski

Strongly regular graphs on 81 vertices and a new partial geometry

In this talk we will explain a method for constructing strongly regular graphs from groups. Using the method, twelve new strongly regular graphs with parameters (81, 30, 9, 12) are found as graphs invariant under certain subgroups of the automorphism groups of the two previously known graphs that arise from 2-weight codes. One of these new graphs is geometric and yields a partial geometry with parameters pg(5, 5, 2) that is not isomorphic to the partial geometry discovered by J. H. van Lint and A. Schrijver in 1981.

strongly regular graph ; partial geometry

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