Spin content of the nucleon in a valence and sea quark mixing model

A dynamical valence and sea quark mixing model is shown to fit the baryon ground state properties as well as the spin content of the nucleon. The relativistic correction and the $q^3{\leftrightarrow} q^3q\bar{q}$ transition terms induced by the quark axial vector current $\bar{\psi}\vec{\gamma}\gamma^5\psi$ in this model space is responsible for the quark spin reduction.