Coloring sparse random Cayley graphs

Abstract

It is shown that there exists $c>0$ so that the Cayley graph over any finite abelian group $Z$ generated by $c\log |Z|$ random elements is properly 3-colorable with high probability (as $|Z|\to \infty$). This is asymptotically tight and improves the best-known bound due to Alon of $\frac{1}{4}\log \log |Z|$ elements. It also settles the abelian case of Alon's suggestion that a bound of $c\log |G|$ may hold for any finite solvable group $G$.

16 pages; exposition improved