Linked from
The 11 pages that link to Laplacian matrix, each with the reason it gives.
Incidence matrixRelated: For an oriented incidence matrix B, the product BBᵀ is the graph Laplacian.
Undirected graphRelated: For undirected graphs, its symmetry links connectivity to eigenvalues.
Kirchhoff's theoremBroader topic: Its principal cofactors contain the spanning-tree count.
Ioana DumitriuRelated: Its spectrum turns network questions into problems about eigenvalues.