Duality and pomeron effective theory for QCD at high energy and large Nc

We propose an effective theory which governs pomeron dynamics in QCD at high energy, in the leading logarithmic approximation, and in the limit where Nc, the number of colors, is large. In spite of its remarkably simple structure, this effective theory generates precisely the evolution equations for scattering amplitudes that have been recently deduced from a more complete microscopic analysis. It accounts for the BFKL evolution of the pomerons together with their interactions: dissociation (one pomeron splitting into two) and recombination (two pomerons merging into one). It is constructed by exploiting a duality principle relating the evolutions in the target and the projectile, more precisely, splitting and merging processes, or fluctuations in the dilute regime and saturation effects in the dense regime. The simplest pomeron loop calculated with the effective theory is free of both ultraviolet or infrared singularities.