  Aggregation of like-charged polymers is widely observed in biological and
soft matter systems. In many systems, bundles are formed when a short-range
attraction of diverse physical origin like charge-bridging, hydrogen-bonding or
hydrophobic interaction, overcomes the longer- range charge repulsion. In this
Letter, we present a general mechanism of bundle formation in these systems as
the breaking of the translational invariance in parallel aligned polymers with
competing interactions of this type. We derive a criterion for finite-sized
bundle formation as well as for macroscopic phase separation (formation of
infinite bundles).
