Extreme Values of the Fiedler Vector on Trees
Let $G$ be a connected tree on $n$ vertices and let $L = D-A$ denote the Laplacian matrix on $G$. The second-smallest eigenvalue $λ_{2}(G) > 0$, also known as the algebraic connectivity, as well as the associated eigenvector $ϕ_2$ have been of substantial interest. We investigate the question of when the maxima and minima of $ϕ_2$ are assumed at the endpoints of the longest path in $G$. Our results also apply to more general graphs that `behave globally' like a tree but can exhibit more complicated local structure. The crucial new ingredient is a reproducing formula for the eigenvector $ϕ_k$.
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