Improved Approximation for the Directed Spanner Problem
Arnab Bhattacharyya, Konstantin Makarychev · arXiv (Cornell University) · 2010
We prove that the size of the sparsest directed k-spanner of a graph can be approximated in polynomial time to within a factor of $\tilde{O}(\sqrt{n})$, for all k >= 3. This improves the $\tilde{O}(n^{2/3})$-approximation recently shown by Dinitz and Krauthgamer.