Consistent gauge invariant nucleon spin decomposition

Understand

We consider a non-uniqueness problem of gauge invariant nucleon spin decomposition.

• A gauge invariant decomposition with a generalized Coulomb constraint for the physical gluon has been constructed.
• The decomposition scheme is consistent with the concept of helicity in non-Abelian gauge theory.
• We provide an explicit representation for the gauge invariant Abelian projection which implies further separation of gluon into binding and valence parts.