The study of multi-particle correlations is a powerful tool to probe the mechanism of particle production in high-energy collisions of protons and nuclei. The LHC p-Pb run led to some interesting observations by ALICE, ATLAS and CMS. The observed patterns are reminiscent of collective effects measured in Pb-Pb collisions. They have been attributed to mechanisms that involve initial-state effects such as gluon saturation and collective effects developing in a high-density system possibly formed in these collisions.
The talk will give an overview of the findings in p-Pb collisions and their theoretical implications.