New Feasibility Conditions for Directed Strongly Regular Graphs

  • Sylvia A. Hobart
  • Jason Williford
Keywords: Directed strongly regular graph


We prove two results for directed strongly regular graphs that have an eigenvalue of multiplicity less than $k$, the common out-degree of each vertex. The first bounds the size of an independent set, and the second determines an eigenvalue of the subgraph on the out-neighborhood of a vertex. Both lead to new nonexistence results for parameter sets.
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