Perturbative generation of a strange-quark asymmetry in the nucleon

We point out that perturbative evolution in QCD at three loops generates a strange-antistrange asymmetry s(x)-(s) over bar (x) in the nucleon's sea just from the fact that the nucleon has nonvanishing up and down quark valence densities. The recently computed three-loop splitting functions allow for an estimate of this effect. We find that a fairly sizable asymmetry may be generated. Results for analogous asymmetries in the heavy-quark sector are also presented.