2014/10/22 by Koutis, Ioannis, Miller, Gary, Peng, Richard
#Discrete Mathematics (cs.DM) #FOS: Computer and information sciences
paper · doi:10.48550/arxiv.1412.6075
The generalized conductance ϕ(G,H) between two graphs G and H on the same vertex set V is defined as the ratio ϕ(G,H) = minS⊆ V \fraccapG(S,S) capH(S,S), where capG(S,S) is the total weight of the edges crossing from S to S=V-S. We show that the minimum generalized eigenvalue λ(LG,LH) of the pair of Laplacians LG and LH satisfies λ(LG,LH) ≥ ϕ(G,H) ϕ(G)/8, where ϕ(G) is the usual conductance of G. A generalized cut that meets this bound can be obtained from the generalized eigenvector corresponding to λ(LG,LH). The inequality complements a recent proof that ϕ(G) cannot be replaced by Θ(ϕ(G,H)) in the above inequality, unless the Unique Games Conjecture is false.