Strongly regular graph

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In graph theory, a strongly regular graph (SRG) is a regular graph G = (V, E) with v vertices and degree k such that for some given integers λ , μ ≥ 0 {\displaystyle \lambda ,\mu \geq 0} every two adjacent vertices have λ common neighbours, and every two non-adjacent vertices have μ common neighbours. Such a strongly regular graph is denoted by srg(v, k, λ, μ). Its complement graph is also strongly regular: it is an srg(v, v − k − 1, v − 2 − 2k + μ, v − 2k + λ). If a graph G is strongly regular with μ > 0, then G is distance-regular with diameter 2. Likewise, if G is strongly regular with λ = 1, then it is locally linear.

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