Is gauge-invariant complete decomposition of the nucleon spin possible ?

Understand

Is gauge-invariant complete decomposition of the nucleon spin possible? Although it is a difficult theoretical question which has not reached a complete consensus yet, a general agreement now is that there are at least two physically inequivalent gauge-invariant decompositions (I) and (II) of the nucleon.

• %The one is a nontrivial gauge-invariant %generalization of the Jaffe-Manohar decomposition.
• %The other is an extension of the Ji decomposition, which allows %a gauge-invariant decomposition of the total gluon angular %momentum into the intrinsic spin and orbital parts.
• In these two decompositions, the intrinsic spin parts of quarks and gluons are just common.