weighted matrix tree theorem

Tags: #theorem

Statement

for a weighted graph G,

∑T spans Gwt(T)=det(L~)

where L~ is any cofactor of the Laplacian (Kirchoff) matrix and the weight of the tree is defined as

wt(T)=∏e∈Txe

Proof

The proof follows from Kirchoff's matrix tree theorem, as we may take each edge weight to be in Z≥0 and treat them as multiedges.