New strongly regular graphs from finite geometries via switching
نویسندگان
چکیده
منابع مشابه
New strongly regular graphs from switching of edges
By Seidel’s switching, we construct new strongly regular graphs with parameters (276, 140, 58, 84). In this paper, we simplify the known switching theorem due to Bose and Shrikhande as follows. Let G = (V,E) be a primitive strongly regular graph with parameters (v, k, λ, μ). Let S(G,H) be the graph from G by switching with respect to a nonempty H ⊂ V . Suppose v = 2(k − θ1) where θ1 is the nont...
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(otherwise we divide the vector by an appropriate scalar), so w.l.o.g. we have uj = 1 for a certain j ∈ {1, . . . , v}. The absolute value |(A~u)j| of the j-th component of A~u is at most ∑ i∼j |ui|; since the absolute values of all components of ~u are less than or equal to 1, we have ∑ i∼j |ui| ≤ k. On the other hand |(A~u)j| must be equal to |ρuj| = |ρ|, from which we obtain |ρ| ≤ k. If ρ = ...
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ژورنال
عنوان ژورنال: Linear Algebra and its Applications
سال: 2019
ISSN: 0024-3795
DOI: 10.1016/j.laa.2019.07.014