  We construct the effective Hamiltonian which governs the renormalization
group flow of the gluon distribution with increasing energy and in the leading
logarithmic approximation. This Hamiltonian defines a two-dimensional field
theory which involves two types of Wilson lines: longitudinal Wilson lines
which describe gluon recombination (or merging) and temporal Wilson lines which
account for gluon bremsstrahlung (or splitting). The Hamiltonian is self-dual,
i.e., it is invariant under the exchange of the two types of Wilson lines. In
the high density regime where one can neglect gluon number fluctuations, the
general Hamiltonian reduces to that for the JIMWLK evolution. In the dilute
regime where gluon recombination becomes unimportant, it reduces to the dual
partner of the JIMWLK Hamiltonian, which describes bremsstrahlung.
