  Charge fractionalization is the phenomenon where quasi-particle excitations
in a many-particle system appear with non-integer values relative to the
fundamental charge unit. Examples of such systems are known from field
theoretical models and from physical realizations. Recently there has been an
interest in charge fractionalization in one-dimensional systems described by
Luttinger liquid theory. These are gapless systems and that gives rise to the
question whether non-integer charges should be regarded as sharp in the same
meaning as in a gapped system. In this talk I first give an introduction to
charge fractionalization as an effect in gapped systems and discuss next in
what sense the charge fractionalization effect is found in gapless Luttinger
liquids. The talk is based on a recent paper with Mats Horsdal and Thors Hans
Hansson.
