Treffer: Approximating k-outconnected subgraph problems.

We present approximation algorithms and structural results for problems in network design. We give improved approximation algorithms for finding min-cost k-outconnected graphs with either a single root or multiple roots for (i) uniform costs, and (ii) metric costs. The improvements are obtained by focusing on single-root k-outconnected graphs and proving (i) a version of Mader's critical cycle theorem and (ii) an extension of a splitting off theorem by Bienstock et al. [ABSTRACT FROM AUTHOR]