Spectral Graph Theory
Laplacian Eigenvalues, Connectivity & Cheeger Constant
Eigenvalues: —
The graph Laplacian L = D − A has eigenvalues 0 = λ₁ ≤ λ₂ ≤ … ≤ λₙ.
λ₂ (Fiedler value) = algebraic connectivity. λ₂ = 0 iff graph is disconnected.
Nodes colored by Fiedler eigenvector (graph partitioning / spectral bisection).