  We present experimental results and a systematic theoretical analysis of
dark-br ight soliton interactions and multiple-dark-bright soliton complexes in
atomic t wo-component Bose-Einstein condensates. We study analytically the
interactions b etween two-dark-bright solitons in a homogeneous condensate and,
then, extend ou r considerations to the presence of the trap. An effective
equation of motion is derived for the dark-bright soliton center and the
existence and stability of stationary two-dark-bright soliton states is
illustrated (with the bright components being either in- or out-of-phase). The
equation of motion provides the characteristic oscillation frequencies of the
solitons, in good agreement with the eigenfrequencies of the anomalous modes of
the system.
