  We investigate the quark orbital angular momentum of the nucleon in the
absence of gauge-field degrees of freedom, by using the concept of the Wigner
distribution and the light-cone wave functions of the Fock state expansion of
the nucleon. The quark orbital angular momentum is obtained from the
phase-space average of the orbital angular momentum operator weighted with the
Wigner distribution of unpolarized quarks in a longitudinally polarized
nucleon. We also derive the light-cone wave function representation of the
orbital angular momentum. In particular, we perform an expansion in the nucleon
Fock state space and decompose the orbital angular momentum into the $N$-parton
state contributions. Explicit expressions are presented in terms of the
light-cone wave functions of the three-quark Fock state. Numerical results for
the up and down quark orbital angular momenta of the proton are shown in the
light-cone constituent quark model and the light-cone chiral quark-soliton
model.
