ANGULAR AND LONG RANGE RAPIDITY CORRELATIONS IN PARTICLE PRODUCTION AT HIGH ENERGY

We discuss the general mechanism leading to long-range rapidity and angular correlations producedin high energy collisions (theridge).This effect naturally appears in the high energy QCD and is strongly sensitive to physics of the gluon saturation.We comment on various recent practical realizations of the main idea, paying special attention to Nc counting and stress the relevance of Pomeron loops.