Perfect Matching in Product Graphs and in their Random Subgraphs

Abstract

For $t\in \mathbb{N}$ and ever $i\in [t]$, let $H_i$ be a $d_i$-regular connected graph with $1<|V(H_i)|\le M$ for some integer $M\ge 2$. Let $G={\square }_{i=1}^t{H}_i$ be the $t$-dimensional Cartesian product of $H_1,\dots ,H_t$. We prove that if $t\ge 2\ln M$ then $G$ has a (nearly-)perfect matching. We further show that this bound on the dimension is tight up to a constant factor. Then, considering the random graph process on $G$, we generalise the result of Bollobás on the binary hypercube $Q^t$, showing that with high probability, the hitting times for minimum degree one, connectivity, and the existence of a (nearly-)perfect matching in the random graph process on $G$ are the same.

arXiv commentA new (tight) Theorem added, proofs revised