On Stability of Rooted Graph and Its Optimality
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Key words:
- rooted graph;reliability;stability;deletion-contraction edge formula;expect-variance optimality /
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Abstract: When G is a rooted graph where each edge may independently succeed with probability p when catastrophic thing happens, we consider the expected number of vertices in the operational component of G containing the root.Then the expected value of edges number EV(G;p) is a proper index of reliability to rooted graph.Later, we give the definition E2(G;p), which is the expect of vertices number square, then variance D(G;p)=E2(G;p)-[EV(G;p)]2.Especially, we get the deletion-contraction edge formula of E2(G;p).So we obtain a recursive computing variance method.And D(G;p) is a proper stability index to the rooted graph.With this formula, we get some variance computational formulas of specific rooted graphs.Finally, we propose expect-variance optimality of rooted graph.