Light flavor sea-quark asymmetry for the spin-dependent distribution functions of the nucleon

The theoretical predictions of the chiral quark soliton model for the unpolarized and longitudinally polarized structure functions of the nucleon are compared with recent high energy data. The theory is shown to explain all the qualitatively noticeable features of the existing experiments, including the light flavor sea-quark asymmetry for the unpolarized distribution functions established by the NMC measurement as well as very small quark spin fraction of the nucleon indicated by the EMC measurement. Another unique feature of the model is that it predicts sizably large isospin asymmetry also for the spin-dependent sea-quark distribution functions.