On random k-out sub-graphs of large graphs

Abstract

We consider random sub-graphs of a fixed graph $G=(V,E)$ with large minimum degree. We fix a positive integer $k$ and let $G_k$ be the random sub-graph where each $v\in V$ independently chooses $k$ random neighbors, making $kn$ edges in all. When the minimum degree $\delta (G)\ge (\frac{1}{2}+\epsilon )n,n=|V|$ then $G_k$ is $k$-connected w.h.p. for $k=O(1)$; Hamiltonian for $k$ sufficiently large. When $\delta (G)\ge m$, then $G_k$ has a cycle of length $(1-\epsilon )m$ for $k\ge k_{\epsilon }$. By w.h.p. we mean that the probability of non-occurrence can be bounded by a function $\varphi (n)$ (or $\varphi (m)$) where ${\lim }_{n\to \infty }\varphi (n)=0$.