The proton spin decomposition : path dependence and gauge symmetry

Understand

We discuss the different types of decomposition of the proton spin.

• We stress that, despite their lack of uniqueness, the Chen et al.
• and Wakamatsu decompositions are perfectly measurable.
• We argue that a large part of the recent controversies boils down to the fact that there actually exist two types of gauge transformations in the Chen et al.