The rainbow connection number of 2-connected graphs
  The rainbow connection number of a graph G is the least number of colours in a (not necessarily proper) edge-colouring of G such that every two vertices are joined by a path which contains no colour twice. Improving a result of Caro et al., we prove that the rainbow connection number of every 2-connected graph with n vertices is at most the ceiling of n/2. The bound is optimal. 
Jan Ekstein, P\v{r}emysl Holub, Tom\'a\v{s} Kaiser, Maria Koch,   Stephan Matos Camacho, Zden\v{e}k Ryj\'a\v{c}ek and Ingo S...
math.CO